TY  - JOUR
A1  - Calitri, Francesca
A1  - Sommer, Michael
A1  - van der Meij, Marijn W.
A1  - Egli, Markus
T1  - Soil erosion along a transect in a forested catchment: recent or ancient processes?
JF  - Catena : an interdisciplinary journal of soil science, hydrology, geomorphology focusing on geoecology and landscape evolution
N2  - Forested areas are assumed not to be influenced by erosion processes. However, forest soils of Northern Germany in a hummocky ground moraine landscape can sometimes exhibit a very shallow thickness on crest positions and buried soils on slope positions. The question consequently is: Are these on-going or ancient erosional and depositional processes? Plutonium isotopes act as soil erosion/deposition tracers for recent (last few decades) processes. Here, we quantified the 239+240PU inventories in a small, forested catchment (ancient forest "Melzower Forst", deciduous trees), which is characterised by a hummocky terrain including a kettle hole. Soil development depths (depth to C horizon) and 239+240PU inventories along a catena of sixteen different profiles were determined and correlated to relief parameters. Moreover, we compared different modelling approaches to derive erosion rates from Pu data. <br /> We find a strong relationship between soil development depths, distance-to-sink and topography along the catena. Fully developed Retisols (thicknesses > 1 m) in the colluvium overlay old land surfaces as documented by fossil Ah horizons. However, we found no relationship of Pu-based erosion rates to any relief parameter. Instead, 239+240PU inventories showed a very high local, spatial variability (36-70 Bq m(-2)). Low annual rainfall, spatially distributed interception and stem flow might explain the high variability of the 239+240PU inventories, giving rise to a patchy input pattern. Different models resulted in quite similar erosion and deposition rates (max: -5 t ha(-1) yr(-1) to +7.3 t ha(-1) yr(-1)). Although some rates are rather high, the magnitude of soil erosion and deposition - in terms of soil thickness change - is negligible during the last 55 years. The partially high values are an effect of the patchy Pu deposition on the forest floor. This forest has been protected for at least 240 years. Therefore rather natural events and anthropogenic activities during medieval times or even earlier must have caused the observed soil pattern, which documents strong erosion and deposition processes.
KW  - Soil erosion
KW  - 239+240 Plutonium
KW  - Forest
KW  - Moraine landscape
KW  - Soil catena
Y1  - 2020
U6  - https://doi.org/10.1016/j.catena.2020.104683
SN  - 0341-8162
SN  - 1872-6887
VL  - 194
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Zhang, Liyu
A1  - Chen, Daizhao
A1  - Kuang, Guodun
A1  - Guo, Zenghui
A1  - Zhang, Gongjing
A1  - Wang, Xia
T1  - Persistent oxic deep ocean conditions and frequent volcanic activities during the Frasnian-Famennian transition recorded in South China
JF  - Global and planetary change
N2  - The Frasnian-Famennian (F-F) transition of Late Devonian was a critical episode in geological history, recording a major mass extinction event. In this study, we focus on an F-F succession from a deep marine context in Bancheng, southern Guangxi, South China, to investigate coeval changes in pelagic environments of the Paleo-Tethys Ocean. The studied succession is exclusively composed of bedded cherts intercalated with multiple siliceous volcanic ash beds. A SIMS zircon U-Pb Concordia age of 367.8 +/- 2.5 Ma is reported for a tuffaceous layer slightly above the F-F boundary. Geochemical ratios of Al/(Al + Fe + Mn), Ce/Ce*, Y/Ho, and Al, Fe contents in bedded cherts indicate that they are of predominantly biogenic/chemical origin with some terrigenous inputs. Negligible enrichment of redox sensitive elements (Mo, U, V) and low V/Cr ratios (<2) suggest persistently oxic conditions existed in the deep pelagic basin at Bancheng, South China during the F-F transition. These findings call into question the widely held hypothesis that marine anoxia was the primary killing mechanism for the F-F crisis. In contrast, multiple tuffaceous layers throughout the F-F boundary succession indicate frequent volcanic activity, which could have released massive amounts of greenhouse gases into the atmosphere, inducing climate warming. This scenario may have increased continental weathering and riverine fluxes into the ocean, reconciling the increases in Al2O3 content and Al/(Al + Fe + Mn) ratio across the F-F boundary. Documentation of persistently oxic conditions and frequent volcanic activitiy provides new perspectives on the inter-relationship between volcanism, climate, and oceanic redox fluctuation during the F-F biotic crisis.
KW  - Late Devonian
KW  - Bedded chert
KW  - Major and trace elements
KW  - Deep ocean redox condition
KW  - Volcanic activity
KW  - Zircon U-Pb dating
Y1  - 2020
U6  - https://doi.org/10.1016/j.gloplacha.2020.103350
SN  - 0921-8181
VL  - 195
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Brill, Fabio Alexander
A1  - Passuni Pineda, Silvia
A1  - Espichan Cuya, Bruno
A1  - Kreibich, Heidi
T1  - A data-mining approach towards damage modelling for El Nino events in Peru
JF  - Geomatics, natural hazards and risk
N2  - Compound natural hazards likeEl Ninoevents cause high damage to society, which to manage requires reliable risk assessments. Damage modelling is a prerequisite for quantitative risk estimations, yet many procedures still rely on expert knowledge, and empirical studies investigating damage from compound natural hazards hardly exist. A nationwide building survey in Peru after theEl Ninoevent 2017 - which caused intense rainfall, ponding water, flash floods and landslides - enables us to apply data-mining methods for statistical groundwork, using explanatory features generated from remote sensing products and open data. We separate regions of different dominant characteristics through unsupervised clustering, and investigate feature importance rankings for classifying damage via supervised machine learning. Besides the expected effect of precipitation, the classification algorithms select the topographic wetness index as most important feature, especially in low elevation areas. The slope length and steepness factor ranks high for mountains and canyons. Partial dependence plots further hint at amplified vulnerability in rural areas. An example of an empirical damage probability map, developed with a random forest model, is provided to demonstrate the technical feasibility.
KW  - Natural hazard
KW  - damage model
KW  - residential buildings
KW  - data-mining
KW  - remote
KW  - sensing
KW  - open data
Y1  - 2020
U6  - https://doi.org/10.1080/19475705.2020.1818636
SN  - 1947-5705
SN  - 1947-5713
VL  - 11
IS  - 1
SP  - 1966
EP  - 1990
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Wietzke, Luzie M.
A1  - Merz, Bruno
A1  - Gerlitz, Lars
A1  - Kreibich, Heidi
A1  - Guse, Björn
A1  - Castellarin, Attilio
A1  - Vorogushyn, Sergiy
T1  - Comparative analysis of scalar upper tail indicators
JF  - Hydrological sciences journal = Journal des sciences hydrologiques
N2  - Different upper tail indicators exist to characterize heavy tail phenomena, but no comparative study has been carried out so far. We evaluate the shape parameter (GEV), obesity index, Gini index and upper tail ratio (UTR) against a novel benchmark of tail heaviness - the surprise factor. Sensitivity analyses to sample size and changes in scale-to-location ratio are carried out in bootstrap experiments. The UTR replicates the surprise factor best but is most uncertain and only comparable between records of similar length. For samples with symmetric Lorenz curves, shape parameter, obesity and Gini indices provide consistent indications. For asymmetric Lorenz curves, however, the first two tend to overestimate, whereas Gini index tends to underestimate tail heaviness. We suggest the use of a combination of shape parameter, obesity and Gini index to characterize tail heaviness. These indicators should be supported with calculation of the Lorenz asymmetry coefficients and interpreted with caution.
KW  - upper tail behaviour
KW  - heavy-tailed distributions
KW  - extremes
KW  - diagnostics
KW  - surprise
Y1  - 2020
U6  - https://doi.org/10.1080/02626667.2020.1769104
SN  - 0262-6667
SN  - 2150-3435
VL  - 65
IS  - 10
SP  - 1625
EP  - 1639
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Kruse, Stefan
A1  - Kolmogorov, Aleksey I.
A1  - Pestryakova, Luidmila Agafyevna
A1  - Herzschuh, Ulrike
T1  - Long-lived larch clones may conserve adaptations that could restrict treeline migration in northern Siberia
JF  - Ecology and evolution
N2  - The occurrence of refugia beyond the arctic treeline and genetic adaptation therein play a crucial role of largely unknown effect size. While refugia have potential for rapidly colonizing the tundra under global warming, the taxa may be maladapted to the new environmental conditions. Understanding the genetic composition and age of refugia is thus crucial for predicting any migration response. 
Here, we genotype 194 larch individuals from an similar to 1.8 km(2)area in northcentral Siberia on the southern Taimyr Peninsula by applying an assay of 16 nuclear microsatellite markers. For estimating the age of clonal individuals, we counted tree rings at sections along branches to establish a lateral growth rate that was then combined with geographic distance.
Findings reveal that the predominant reproduction type is clonal (58.76%) by short distance spreading of ramets. One outlier of clones 1 km apart could have been dispersed by reindeer. In clonal groups and within individuals, we find that somatic mutations accumulate with geographic distance. Clonal groups of two or more individuals are observed. Clonal age estimates regularly suggest individuals as old as 2,200 years, which coincides with a major environmental change that forced a treeline retreat in the region. 
We conclude that individuals with clonal growth mode were naturally selected as it lowers the likely risk of extinction under a harsh environment. We discuss this legacy from the past that might now be a maladaptation and hinder expansion under currently strongly increasing temperatures.
KW  - adaptation
KW  - clonal growth
KW  - growth rate
KW  - Larix
KW  - leading edge
KW  - treeline
KW  - migration
Y1  - 2020
U6  - https://doi.org/10.1002/ece3.6660
SN  - 2045-7758
VL  - 10
IS  - 18
SP  - 10017
EP  - 10030
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Voss, Katalyn A.
A1  - Bookhagen, Bodo
A1  - Sachse, Dirk
A1  - Chadwick, Oliver A.
T1  - Variation of deuterium excess in surface waters across a 5000-m elevation gradient in eastern Nepal
JF  - Journal of hydrology
N2  - The strong elevation gradient of the Himalaya allows for investigation of altitude and orographic impacts on surface water delta O-18 and delta D stable isotope values. This study differentiates the time- and altitude-variable contributions of source waters to the Arun River in eastern Nepal. It provides isotope data along a 5000-m gradient collected from tributaries as well as groundwater, snow, and glacial-sourced surface waters and time-series data from April to October 2016. We find nonlinear trends in delta O-18 and delta D lapse rates with high-elevation lapse rates (4000-6000 masl) 5-7 times more negative than low-elevation lapse rates (1000-3000 masl). A distinct seasonal signal in delta O-18 and delta D lapse rates indicates time-variable source-water contributions from glacial and snow meltwater as well as precipitation transitions between the Indian Summer Monsoon and Winter Westerly Disturbances. Deuterium excess correlates with the extent of snowpack and tracks melt events during the Indian Summer Monsoon season. Our analysis identifies the influence of snow and glacial melt waters on river composition during low-flow conditions before the monsoon (April/May 2016) followed by a 5-week transition to the Indian Summer Monsoon-sourced rainfall around mid-June 2016. In the post-monsoon season, we find continued influence from glacial melt waters as well as ISM-sourced groundwater.
KW  - stable isotopes
KW  - Himalaya
KW  - glacier
KW  - snow
KW  - precipitation
KW  - seasonality
Y1  - 2020
U6  - https://doi.org/10.1016/j.jhydrol.2020.124802
SN  - 0022-1694
SN  - 1879-2707
VL  - 586
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Ganguli, Poulomi
A1  - Paprotny, Dominik
A1  - Hasan, Mehedi
A1  - Güntner, Andreas
A1  - Merz, Bruno
T1  - Projected changes in compound flood hazard from riverine and coastal floods in northwestern Europe
JF  - Earth's future
N2  - Compound flooding in coastal regions, that is, the simultaneous or successive occurrence of high sea levels and high river flows, is expected to increase in a warmer world. To date, however, there is no robust evidence on projected changes in compound flooding for northwestern Europe. We combine projected storm surges and river floods with probabilistic, localized relative sea-level rise (SLR) scenarios to assess the future compound flood hazard over northwestern coastal Europe in the high (RCP8.5) emission scenario. We use high-resolution, dynamically downscaled regional climate models (RCM) to drive a storm surge model and a hydrological model, and analyze the joint occurrence of high coastal water levels and associated river peaks in a multivariate copula-based approach. The RCM-forced multimodel mean reasonably represents the observed spatial pattern of the dependence strength between annual maxima surge and peak river discharge, although substantial discrepancies exist between observed and simulated dependence strength. All models overestimate the dependence strength, possibly due to limitations in model parameterizations. This bias affects compound flood hazard estimates and requires further investigation. While our results suggest decreasing compound flood hazard over the majority of sites by 2050s (2040-2069) compared to the reference period (1985-2005), an increase in projected compound flood hazard is limited to around 34% of the sites. Further, we show the substantial role of SLR, a driver of compound floods, which has frequently been neglected. Our findings highlight the need to be aware of the limitations of the current generation of Earth system models in simulating coastal compound floods.
KW  - compound flood
KW  - storm surge
KW  - river floods
KW  - sea level rise
KW  - climate
KW  - change
KW  - Europe
Y1  - 2020
U6  - https://doi.org/10.1029/2020EF001752
SN  - 2328-4277
VL  - 8
IS  - 11
PB  - Wiley-Blackwell
CY  - Hoboken, NJ
ER  - 
TY  - JOUR
A1  - Vogt-Vincent, Noam
A1  - Lippold, Jörg
A1  - Kaboth-Bahr, Stefanie
A1  - Blaser, Patrick
T1  - Ice-rafted debris as a source of non-conservative behaviour for the epsilon Nd palaeotracer
BT  - insights from a simple model
JF  - Geo-marine letters : an international journal of marine geology
N2  - Neodymium isotopic composition (epsilon Nd) has enjoyed widespread use as a palaeotracer, principally because it behaves quasi-conservatively in the modern ocean. However, recent bottom water epsilon Nd reconstructions from the eastern North Atlantic are difficult to interpret under assumptions of conservative behaviour. The observation that this apparent departure from conservative behaviour increases with enhanced ice-rafted debris (IRD) fluxes has resulted in the suggestion that IRD leads to the overprinting of bottom water epsilon Nd through reversible scavenging. In this study, a simple water column model successfully reproduces epsilon Nd reconstructions from the eastern North Atlantic at the Last Glacial Maximum and Heinrich Stadial 1, and demonstrates that the changes in scavenging intensity required for good model-data fit is in good agreement with changes in the observed IRD flux. Although uncertainties in model parameters preclude a more definitive conclusion, the results indicate that the suggestion of IRD as a source of non-conservative behaviour in the epsilon Nd tracer is reasonable and that further research into the fundamental chemistry underlying the marine neodymium cycle is necessary to increase confidence in assumptions of conservative epsilon Nd behaviour in the past.
KW  - Neodymium isotopes
KW  - epsilon Nd
KW  - ice-rafted debris
KW  - IRD
KW  - last glacial
KW  - maximum
KW  - LGM
KW  - Heinrich event
KW  - Palaeoceanography
KW  - Paleoceanography
KW  - model
KW  - reversible scavenging
KW  - conservative
KW  - ocean circulation
KW  - atlantic
KW  - meridional overturning circulation
KW  - geochemical cycling
Y1  - 2020
U6  - https://doi.org/10.1007/s00367-020-00643-x
SN  - 0276-0460
SN  - 1432-1157
VL  - 40
IS  - 3
SP  - 325
EP  - 340
PB  - Springer
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Huang, Sichao
A1  - Herzschuh, Ulrike
A1  - Pestryakova, Luidmila Agafyevna
A1  - Zimmermann, Heike Hildegard
A1  - Davydova, Paraskovya
A1  - Biskaborn, Boris
A1  - Shevtsova, Iuliia
A1  - Stoof-Leichsenring, Kathleen Rosemarie
T1  - Genetic and morphologic determination of diatom community composition in surface sediments from glacial and thermokarst lakes in the Siberian Arctic
JF  - Journal of paleolimnolog
N2  - Lakes cover large parts of the climatically sensitive Arctic landscape and respond rapidly to environmental change. Arctic lakes have different origins and include the predominant thermokarst lakes, which are small, young and highly dynamic, as well as large, old and stable glacial lakes. Freshwater diatoms dominate the primary producer community in these lakes and can be used to detect biotic responses to climate and environmental change. We used specific diatom metabarcoding on sedimentary DNA, combined with next-generation sequencing and diatom morphology, to assess diatom diversity in five glacial and 15 thermokarst lakes within the easternmost expanse of the Siberian treeline ecotone in Chukotka, Russia. We obtained 163 verified diatom sequence types and identified 176 diatom species morphologically. Although there were large differences in taxonomic assignment using the two approaches, they showed similar high abundances and diversity of Fragilariceae and Aulacoseiraceae. In particular, the genetic approach detected hidden within-lake variations of fragilarioids in glacial lakes and dominance of centric Aulacoseira species, whereas Lindavia ocellata was predominant using morphology. In thermokarst lakes, sequence types and valve counts also detected high diversity of Fragilariaceae, which followed the vegetation gradient along the treeline. Ordination analyses of the genetic data from glacial and thermokarst lakes suggest that concentrations of sulfate (SO42-), an indicator of the activity of sulfate-reducing microbes under anoxic conditions, and bicarbonate (HCO3-), which relates to surrounding vegetation, have a significant influence on diatom community composition. For thermokarst lakes, we also identified lake depth as an important variable, but SO42- best explains diatom diversity derived from genetic data, whereas HCO3- best explains the data from valve counts. Higher diatom diversity was detected in glacial lakes, most likely related to greater lake age and different edaphic settings, which gave rise to diversification and endemism. In contrast, small, dynamic thermokarst lakes are inhabited by stress-tolerant fragilarioids and are related to different vegetation types along the treeline ecotone. Our study demonstrated that genetic investigations of lake sediments can be used to interpret climate and environmental responses of diatoms. It also showed how lake type affects diatom diversity, and that such genetic analyses can be used to track diatom community changes under ongoing warming in the Arctic.
KW  - diatoms
KW  - diversity
KW  - glacial lakes
KW  - sedimentary DNA
KW  - Siberian arctic
KW  - thermokarst
Y1  - 2020
U6  - https://doi.org/10.1007/s10933-020-00133-1
SN  - 0921-2728
SN  - 1573-0417
VL  - 64
IS  - 3
SP  - 225
EP  - 242
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Guzman, Diego A.
A1  - Samprogna Mohor, Guilherme
A1  - Mendiondo, Eduardo Mario
T1  - Multi-year index-based insurance for adapting Water Utility Companies to hydrological drought
BT  - case study of a water supply system of the Sao Paulo metropolitan region, Brazil
JF  - Water
N2  - The sustainability of water utility companies is threatened by non-stationary drivers, such as climate and anthropogenic changes. To cope with potential economic losses, instruments such as insurance are useful for planning scenarios and mitigating impacts, but data limitations and risk uncertainties affect premium estimation and, consequently, business sustainability. This research estimated the possible economic impacts of business interruption to the Sao Paulo Water Utility Company derived from hydrological drought and how this could be mitigated with an insurance scheme. Multi-year insurance (MYI) was proposed through a set of "change" drivers: the climate driver, through forcing the water evaluation and planning system (WEAP) hydrological tool; the anthropogenic driver, through water demand projections; and the economic driver, associated with recent water price policies adopted by the utility company during water scarcity periods. In our study case, the evaluated indices showed that MYI contracts that cover only longer droughts, regardless of the magnitude, offer better financial performance than contracts that cover all events (in terms of drought duration). Moreover, through MYI contracts, we demonstrate solvency for the insurance fund in the long term and an annual average actuarially fair premium close to the total expected revenue reduction.
KW  - multi-year insurance
KW  - climate change
KW  - hydrological drought
KW  - water
KW  - security and economy
Y1  - 2020
U6  - https://doi.org/10.3390/w12112954
SN  - 2073-4441
VL  - 12
IS  - 11
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Izgi, Gizem
A1  - Eken, Tuna
A1  - Gaebler, Peter
A1  - Eulenfeld, Tom
A1  - Taymaz, Tuncay
T1  - Crustal seismic attenuation parameters in the western region of the North Anatolian Fault Zone
JF  - Journal of geodynamics
N2  - Detailed knowledge of the crustal structure along the North Anatolian Fault Zone can help in understanding past and present tectonic processes in relation to the deformation history. To estimate the frequency-dependent crustal attenuation parameters beneath the western part of the North Anatolian Fault Zone we apply acoustic radiative transfer theory under the assumption of multiple isotropic scattering to generate synthetic seismogram envelopes. The inversion depends on finding an optimal fit between observed and synthetically computed coda wave envelopes in five frequency bands. 2-D lateral variation of intrinsic and scattering attenuation at various frequencies tends to three crustal blocks (i.e., Armutlu-Almacik, Istanbul-Zonguldak and Sakarya Zones) separated by the southern and northern branches of the western part of the North Anatolian Fault Zone. Overall, scattering attenuation appears to be dominant over intrinsic attenuation in the study area at lower frequencies. Relatively low attenuation properties are observed beneath the older Istanbul Zone whereas higher attenuation properties are found for the younger Sakarya Zone. The Armutlu Almacik Zone exhibits more complex lateral variations. Very high attenuation values towards the west characterize the area of the Kuzuluk Basin, a pull-apart basin formed under west-east extension. Our coda-derived moment magnitudes are similar to the local magnitude estimates that were previously calculated for the same earthquakes. For smaller earthquakes (M-L < 2.5), however, the relation between local and moment magnitudes appears to lose its coherency. This may stem from various reasons including the use of seismic data recorded in finite sampling interval, possible biases in local magnitude estimates of earthquake catalogues as well as biases due to wrong assumptions to consider anelastic attenuation terms.
Y1  - 2020
U6  - https://doi.org/10.1016/j.jog.2020.101694
SN  - 0264-3707
VL  - 134
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Reschke, Maria
A1  - Kröner, Igor
A1  - Laepple, Thomas
T1  - Testing the consistency of Holocene and Last Glacial Maximum spatial correlations in temperature proxy records
JF  - Journal of quaternary science : JQS
N2  - Holocene temperature proxy records are commonly used in quantitative synthesis and model-data comparisons. However, comparing correlations between time series from records collected in proximity to one another with the expected correlations based on climate model simulations indicates either regional or noisy climate signals in Holocene temperature proxy records. In this study, we evaluate the consistency of spatial correlations present in Holocene proxy records with those found in data from the Last Glacial Maximum (LGM). Specifically, we predict correlations expected in LGM proxy records if the only difference to Holocene correlations would be due to more time uncertainty and more climate variability in the LGM. We compare this simple prediction to the actual correlation structure in the LGM proxy records. We found that time series data of ice-core stable isotope records and planktonic foraminifera Mg/Ca ratios were consistent between the Holocene and LGM periods, while time series of Uk'37 proxy records were not as we found no correlation between nearby LGM records. Our results support the finding of highly regional or noisy marine proxy records in the compilation analysed here and suggest the need for further studies on the role of climate proxies and the processes of climate signal recording and preservation.
KW  - Holocene
KW  - LGM
KW  - spatial correlation
KW  - temperature
KW  - Uk'37
Y1  - 2020
U6  - https://doi.org/10.1002/jqs.3245
SN  - 0267-8179
SN  - 1099-1417
VL  - 36
IS  - 1
SP  - 20
EP  - 28
PB  - Wiley
CY  - New York
ER  - 
TY  - JOUR
A1  - Zimmermann, Heike Hildegard
A1  - Stoof-Leichsenring, Kathleen Rosemarie
A1  - Kruse, Stefan
A1  - Müller, Juliane
A1  - Stein, Ruediger
A1  - Tiedemann, Ralf
A1  - Herzschuh, Ulrike
T1  - Changes in the composition of marine and sea-ice diatoms derived from sedimentary ancient DNA of the eastern Fram Strait over the past 30 000 years
JF  - Ocean science
N2  - The Fram Strait is an area with a relatively low and irregular distribution of diatom microfossils in surface sediments, and thus microfossil records are scarce, rarely exceed the Holocene, and contain sparse information about past richness and taxonomic composition. These attributes make the Fram Strait an ideal study site to test the utility of sedimentary ancient DNA (sedaDNA) metabarcoding. Amplifying a short, partial rbcL marker from samples of sediment core MSM05/5-712-2 resulted in 95.7% of our sequences being assigned to diatoms across 18 different families, with 38.6% of them being resolved to species and 25.8% to genus level. Independent replicates show a high similarity of PCR products, especially in the oldest samples. Diatom sedaDNA richness is highest in the Late Weichselian and lowest in Mid- and Late Holocene samples. Taxonomic composition is dominated by cold-water and sea-ice-associated diatoms and suggests several reorganisations - after the Last Glacial Maximum, after the Younger Dryas, and after the Early and after the Mid-Holocene. Different sequences assigned to, amongst others, Chaetoceros socialis indicate the detectability of intra-specific diversity using sedaDNA. We detect no clear pattern between our diatom sedaDNA record and the previously published IP25 record of this core, although proportions of pennate diatoms increase with higher IP25 concentrations and proportions of Nitzschia cf. frigida exceeding 2% of the assemblage point towards past sea-ice presence.
Y1  - 2020
U6  - https://doi.org/10.5194/os-16-1017-2020
SN  - 1812-0784
VL  - 16
IS  - 5
SP  - 1017
EP  - 1032
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Montero-Lopez, Carolina
A1  - Hongn, Fernando D.
A1  - Lopez Steinmetz, Romina L.
A1  - Aramayo, Alejandro
A1  - Pingel, Heiko
A1  - Strecker, Manfred
A1  - Cottle, John
A1  - Bianchi, Carlos
T1  - Development of an incipient Paleogene topography between the present-day Eastern Andean Plateau (Puna) and the Eastern Cordillera, southern Central Andes, NW Argentina
JF  - Basin research / publ. in conjunction with the European Association of Geoscientists & Engineers and the International Association of Sedimentologists
N2  - The structural and topographic evolution of orogenic plateaus is an important research topic because of its impact on atmospheric circulation patterns, the amount and distribution of rainfall, and resulting changes in surface processes. The Puna region in the north-western Argentina (between 13 degrees S and 27 degrees S) is part of the Andean Plateau, which is the world's second largest orogenic plateau. In order to investigate the deformational events responsible for the initial growth of this part of the Andean plateau, we carried out structural and stratigraphic investigations within the present-day transition zone between the northern Puna and the adjacent Eastern Cordillera to the east. This transition zone is characterized by ubiquitous exposures of continental middle Eocene redbeds of the Casa Grande Formation. Our structural mapping, together with a sedimentological analysis of these units and their relationships with the adjacent mountain ranges, has revealed growth structures and unconformities that are indicative of syntectonic deposition. These findings support the notion that tectonic shortening in this part of the Central Andes was already active during the middle Paleogene, and that early Cenozoic deformation in the region that now constitutes the Puna occurred in a spatially irregular manner. The patterns of Paleogene deformation and uplift along the eastern margin of the present-day plateau correspond to an approximately north-south oriented swath of reactivated basement heterogeneities (i.e. zones of mechanical weakness) stemming from regional Paleozoic mountain building that may have led to local concentration of deformation belts.
KW  - Andean Plateau
KW  - Eastern Cordillera
KW  - Eocene deformation
KW  - growth structures
KW  - northern Puna
KW  - north-western Argentina
KW  - southern Central Andes
Y1  - 2020
U6  - https://doi.org/10.1111/bre.12510
SN  - 0950-091X
SN  - 1365-2117
VL  - 33
IS  - 2
SP  - 1194
EP  - 1217
PB  - Wiley-Blackwell
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Zhou, Renjie
A1  - Aitchison, Jonathan C.
A1  - Lokho, Kapesa
A1  - Sobel, Edward
A1  - Feng, Yuexing
A1  - Zhao, Jian-xin
T1  - Unroofing the Ladakh Batholith: constraints from autochthonous molasse of the Indus Basin, NW Himalaya
JF  - Journal of the Geological Society
N2  - The Indus Molasse records orogenic sedimentation associated with uplift and erosion of the southern margin of Asia in the course of ongoing India-Eurasia collision. Detailed field investigation clarifies the nature and extent of the depositional contact between this molasse and the underlying basement units. We report the first dataset on detrital zircon U-Pb ages, Hf isotopes and apatite U-Pb ages for the autochthonous molasse in the Indus Suture Zone. A latest Oligocene depositional age is proposed on the basis of the youngest detrital zircon U-Pb age peak and is consistent with published biostratigraphic data. Multiple provenance indicators suggest exclusively northerly derivation with no input from India in the lowermost parts of the section. The results provide constraints on the uplift and erosion history of the Ladakh Range following the initial India-Asia collision.
Y1  - 2020
U6  - https://doi.org/10.1144/jgs2019-188
SN  - 0016-7649
SN  - 2041-479X
VL  - 177
IS  - 4
SP  - 818
EP  - 825
PB  - Geological Society (London)
CY  - London
ER  - 
TY  - JOUR
A1  - Bahr, André
A1  - Kolber, Gilles
A1  - Kaboth-Bahr, Stefanie
A1  - Reinhardt, Lutz
A1  - Friedrich, Oliver
A1  - Pross, Jörg
T1  - Mega-monsoon variability during the late Triassic
BT  - re-assessing the role of orbital forcing in the deposition of playa sediments in the Germanic Basin
JF  - Sedimentology : the journal of the International Association of Sedimentologists
N2  - The formation of the supercontinent Pangaea during the Permo-Triassic gave rise to an extreme monsoonal climate (often termed 'mega-monsoon') that has been documented by numerous palaeo-records. However, considerable debate exists about the role of orbital forcing in causing humid intervals in an otherwise arid climate. To shed new light on the forcing of monsoonal variability in subtropical Pangaea, this study focuses on sediment facies and colour variability of playa and alluvial fan deposits in an outcrop from the late Carnian (ca 225 Ma) in the southern Germanic Basin, south-western Germany. The sediments were deposited against a background of increasingly arid conditions following the humid Carnian Pluvial Event (ca 234 to 232 Ma). The ca 2 center dot 4 Myr long sedimentary succession studied shows a tripartite long-term evolution, starting with a distal mud-flat facies deposited under arid conditions. This phase was followed by a highly variable playa-lake environment that documents more humid conditions and finally a regression of the playa-lake due to a return of arid conditions. The red-green (a*) and lightness (L*) records show that this long-term variability was overprinted by alternating wet/dry cycles driven by orbital precession and ca 405 kyr eccentricity, without significant influence of obliquity. The absence of obliquity in this record indicates that high-latitude forcing played only a minor role in the southern Germanic Basin during the late Carnian. This is different from the subsequent Norian when high-latitude signals became more pronounced, potentially related to the northward drift of the Germanic Basin. The recurring pattern of pluvial events during the late Triassic demonstrates that orbital forcing, in particular eccentricity, stimulated the occurrence and intensity of wet phases. It also highlights the possibility that the Carnian Pluvial Event, although most likely triggered by enhanced volcanic activity, may also have been modified by an orbital stimulus.
KW  - Carnian Pluvial Event
KW  - Germanic Basin
KW  - Late Triassic
KW  - mega-monsoon
KW  - orbital forcing
KW  - playa-lake
Y1  - 2019
U6  - https://doi.org/10.1111/sed.12668
SN  - 0037-0746
SN  - 1365-3091
VL  - 67
IS  - 2
SP  - 951
EP  - 970
PB  - Wiley-Blackwell
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Glerum, Anne
A1  - Brune, Sascha
A1  - Stamps, D. Sarah
A1  - Strecker, Manfred
T1  - Victoria continental microplate dynamics controlled by the lithospheric strength distribution of the East African Rift
JF  - Nature Communications
N2  - The Victoria microplate between the Eastern and Western Branches of the East African Rift System is one of the largest continental microplates on Earth. In striking contrast to its neighboring plates, Victoria rotates counterclockwise with respect to Nubia. The underlying cause of this distinctive rotation has remained elusive so far. Using 3D numerical models, we investigate the role of pre-existing lithospheric heterogeneities in continental microplate rotation. We find that Victoria's rotation is primarily controlled by the distribution of rheologically stronger zones that transmit the drag of the major plates to the microplate and of the mechanically weaker mobile belts surrounding Victoria that facilitate rotation. Our models reproduce Victoria's GPS-derived counterclockwise rotation as well as key complexities of the regional tectonic stress field. These results reconcile competing ideas on the opening of the rift system by highlighting differences in orientation of the far-field divergence, local extension, and the minimum horizontal stress. One of the largest continental microplates on Earth is situated in the center of the East African Rift System, and oddly, the Victoria microplate rotates counterclockwise with respect to the neighboring African tectonic plate. Here, the authors' modelling results suggest that Victoria microplate rotation is caused by edge-driven lithospheric processes related to the specific geometry of rheologically weak and strong regions.
Y1  - 2020
U6  - https://doi.org/10.1038/s41467-020-16176-x
SN  - 2041-1723
VL  - 11
IS  - 1
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - JOUR
A1  - Bentz, Stephan
A1  - Kwiatek, Grzegorz
A1  - Martinez-Garzon, Patricia
A1  - Bohnhoff, Marco
A1  - Dresen, Georg
T1  - Seismic moment evolution during hydraulic stimulations
JF  - Geophysical research letters
N2  - Analysis of past and present stimulation projects reveals that the temporal evolution and growth of maximum observed moment magnitudes may be linked directly to the injected fluid volume and hydraulic energy. Overall evolution of seismic moment seems independent of the tectonic stress regime and is most likely governed by reservoir specific parameters, such as the preexisting structural inventory. Data suggest that magnitudes can grow either in a stable way, indicating the constant propagation of self-arrested ruptures, or unbound, for which the maximum magnitude is only limited by the size of tectonic faults and fault connectivity. Transition between the two states may occur at any time during injection or not at all. Monitoring and traffic light systems used during stimulations need to account for the possibility of unstable rupture propagation from the very beginning of injection by observing the entire seismicity evolution in near-real time and at high resolution for an immediate reaction in injection strategy. 

Plain Language Summary Predicting and controlling the size of earthquakes caused by fluid injection is currently the major concern of many projects associated with geothermal energy production. Here, we analyze the magnitude and seismic moment evolution with injection parameters for prominent geothermal and scientific projects to date. Evolution of seismicity seems to be largely independent of the tectonic stress background and seemingly depends on reservoir specific characteristics. We find that the maximum observed magnitudes relate linearly to the injected volume or hydraulic energy. A linear relation suggests stable growth of induced ruptures, as predicted by current models, or rupture growth may no longer depend on the stimulated volume but on tectonics. A system may change between the two states during the course of fluid injection. Close-by and high-resolution monitoring of seismic and hydraulic parameters in near-real time may help identify these fundamental changes in ample time to change injection strategy and manage maximum magnitudes.
Y1  - 2020
U6  - https://doi.org/10.1029/2019GL086185
SN  - 0094-8276
SN  - 1944-8007
VL  - 47
IS  - 5
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Forbriger, Thomas
A1  - Gao, Lingli
A1  - Malischewsky, Peter
A1  - Ohrnberger, Matthias
A1  - Pan, Yudi
T1  - A single Rayleigh mode may exist with multiple values of phase-velocity at one frequency
JF  - Geophysical journal international
N2  - Other than commonly assumed in seismology, the phase velocity of Rayleigh waves is not necessarily a single-valued function of frequency. In fact, a single Rayleigh mode can exist with three different values of phase velocity at one frequency. We demonstrate this for the first higher mode on a realistic shallow seismic structure of a homogeneous layer of unconsolidated sediments on top of a half-space of solid rock (LOH). In the case of LOH a significant contrast to the half-space is required to produce the phenomenon. In a simpler structure of a homogeneous layer with fixed (rigid) bottom (LFB) the phenomenon exists for values of Poisson's ratio between 0.19 and 0.5 and is most pronounced for P-wave velocity being three times S-wave velocity (Poisson's ratio of 0.4375). A pavement-like structure (PAV) of two layers on top of a half-space produces the multivaluedness for the fundamental mode. Programs for the computation of synthetic dispersion curves are prone to trouble in such cases. Many of them use mode-follower algorithms which loose track of the dispersion curve and miss the multivalued section. We show results for well established programs. Their inability to properly handle these cases might be one reason why the phenomenon of multivaluedness went unnoticed in seismological Rayleigh wave research for so long. For the very same reason methods of dispersion analysis must fail if they imply wave number k(l)(omega) for the lth Rayleigh mode to be a single-valued function of frequency.. This applies in particular to deconvolution methods like phase-matched filters. We demonstrate that a slant-stack analysis fails in the multivalued section, while a Fourier-Bessel transformation captures the complete Rayleigh-wave signal. Waves of finite bandwidth in the multivalued section propagate with positive group-velocity and negative phase-velocity. Their eigenfunctions appear conventional and contain no conspicuous feature.
KW  - Surface waves and free oscillations
KW  - Theoretical seismology
KW  - Wave
KW  - propagation
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa123
SN  - 0956-540X
SN  - 1365-246X
VL  - 222
IS  - 1
SP  - 582
EP  - 594
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Menges, Johanna
A1  - Hovius, Niels
A1  - Andermann, Christoff
A1  - Lupker, Maarten
A1  - Haghipour, Negar
A1  - Märki, Lena
A1  - Sachse, Dirk
T1  - Variations in organic carbon sourcing along a trans-Himalayan river determined by a Bayesian mixing approach
JF  - Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society
N2  - Rivers transfer particulate organic carbon (POC) from eroding mountains into geological sinks. Organic carbon source composition and selective mobilization have been shown to affect the type and quantity of POC export, but their combined effects across complex mountain ranges remain underexplored. Here, we examine the variation in organic carbon sourcing and transport in the trans-Himalayan Kali Gandaki River catchment, along strong gradients in precipitation, rock type and vegetation. Combining bulk stable nitrogen, and stable and radioactive organic carbon isotopic composition of bedrock, litter, soil and river sediment samples with a Bayesian end-member mixing approach, we differentiate POC sources along the river and quantify their export. Our analysis shows that POC export from the Tibetan segment of the catchment, where carbon bearing shales are partially covered by aged and modern soils, is dominated by petrogenic POC. Based on our data we re-assess the presence of aged biospheric OC in this part of the catchment, and its contribution to the river load. In the High Himalayan segment, we observed low inputs of petrogenic and biospheric POC, likely due to very low organic carbon concentrations in the metamorphic bedrock, combined with erosion dominated by deep-seated landslides. Our findings show that along the Kali Gandaki River, the sourcing of sediment and organic carbon are decoupled, due to differences in rock organic carbon content, soil and above ground carbon stocks, and geomorphic process activity. While the fast eroding High Himalayas are the principal source of river sediment, the Tibetan headwaters, where erosion rates are lower, are the principal source of organic carbon. To robustly estimate organic carbon export from the Himalayas, the mountain range should be divided into tectono-physiographic zones with distinct organic carbon yields due to differences in substrate and erosion processes and rates.
KW  - particulate organic carbon
KW  - Himalaya
KW  - rivers
KW  - carbon cycle
KW  - stable
KW  - isotopes
KW  - erosion
KW  - end-member mixing
Y1  - 2020
U6  - https://doi.org/10.1016/j.gca.2020.07.003
SN  - 0016-7037
VL  - 286
SP  - 159
EP  - 176
PB  - Elsevier
CY  - New York [u.a.]
ER  - 
TY  - JOUR
A1  - Obreht, Igor
A1  - Wörmer, Lars
A1  - Brauer, Achim
A1  - Wendt, Jenny
A1  - Alfken, Susanne
A1  - De Vleeschouwer, David
A1  - Elvert, Marcus
A1  - Hinrichs, Kai-Uwe
T1  - An annually resolved record of Western European vegetation response to Younger Dryas cooling
JF  - Quaternary science reviews : the international multidisciplinary research and review journal
N2  - The regional patterns and timing of the Younger Dryas cooling in the North Atlantic realm were complex and are mechanistically incompletely understood. To enhance understanding of regional climate patterns, we present molecular biomarker records at subannual to annual resolution by mass spectrometry imaging (MSI) of sediments from the Lake Meerfelder Maar covering the Allerod-Younger Dryas transition. These analyses are supported by conventional extraction-based molecular-isotopic analyses, which both validate the imaging results and constrain the sources of the target compounds. The targeted fatty acid biomarkers serve as a gauge of the response of the local aquatic and terrestrial ecosystem to climate change. Based on the comparison of our data with existing data from Meerfelder Maar, we analyse the short-term environmental evolution in Western Europe during the studied time interval and confirm the previously reported delayed hydrological response to Greenland cooling. However, despite a detected delay of Western European environmental change of similar to 135 years, our biomarker data show statistically significant correlation with deuterium excess in Greenland ice core at - annual resolution during this time-transgressive cooling. This suggests a coherent atmospheric forcing across the North Atlantic realm during this transition. We propose that Western European cooling was postponed due to major reorganization of the westerlies that were intermittently forcing warmer and wetter air masses from lower latitudes to Western Europe and thus resulted in delayed cooling relative to Greenland.
KW  - lateglacial
KW  - paleoclimatology
KW  - Western Europe
KW  - Meerfelder Maar
KW  - high-resolution biomarkers
KW  - fatty acids
KW  - FT-ICR-MS
KW  - mass spectrometry
KW  - imaging
Y1  - 2020
U6  - https://doi.org/10.1016/j.quascirev.2020.106198
SN  - 0277-3791
VL  - 231
PB  - Elsevier
CY  - Amsterdam [u.a.]
ER  - 
TY  - JOUR
A1  - Krmíček, Lukáš
A1  - Timmerman, Martin Jan
A1  - Ziemann, Martin Andreas
A1  - Sudo, Masafumi
A1  - Ulrych, Jaromir
T1  - 40Ar/39Ar step-heating dating of phlogopite and kaersutite megacrysts from the Železná hůrka (Eisenbühl) Pleistocene scoria cone, Czech Republic
JF  - Geologica Carpathica
N2  - (40)A/Ar-39 step-heating of mica and amphibole megacrysts from hauyne-bearing olivine melilitite scoria/tephra from the Zelezna hurka yielded a 435 +/- 108 ka isotope correlation age for phlogopite and a more imprecise 1.55 Ma total gas age of the kaersutite megacryst. The amphibole megacrysts may constitute the first, and the younger phlogopite megacrysts the later phase of mafic, hydrous melilitic magma crystallization. It cannot be ruled out that the amphibole megacrysts are petrogenetically unrelated to tephra and phlogopite megacrysts and were derived from mantle xenoliths or disaggregated older, deep crustal pegmatites. This is in line both with the rarity of amphibole at Zelezna hurka and with the observed signs of magmatic resorption at the edges of amphibole crystals.
KW  - Bohemian Massif
KW  - Zelezna hurka
KW  - Eisenbuhl
KW  - argon dating
KW  - mica
KW  - amphibole
KW  - melilitite
Y1  - 2020
U6  - https://doi.org/10.31577/GeolCarp.71.4.6
SN  - 1335-0552
SN  - 1336-8052
VL  - 71
IS  - 4
SP  - 382
EP  - 387
PB  - Veda
CY  - Bratislava
ER  - 
TY  - JOUR
A1  - Rybski, Diego
A1  - Dawson, Richard J.
A1  - Kropp, Jürgen
T1  - Comparing generic and case study damage functions
BT  - London storm-surge example
JF  - Natural hazards review
N2  - Two different approaches are used to assess the impacts associated with natural hazards and climate change in cities. A bottom-up approach uses high resolution data on constituent assets within the urban area. In contrast, a top-down approach uses less detailed information but is consequently more readily transferable. Here, we compare damage curves generated by each approach for coastal flooding in London. To compare them, we fit a log-logistic regression with three parameters to the calculated damage curves. We find that the functions are remarkably similar in their shape, albeit with different inflection points and a maximum damage that differs by 13%-25%. If rescaled, the curves agree almost exactly, which enables damage assessment to be undertaken following the calculation of the three parameters.
Y1  - 2020
U6  - https://doi.org/10.1061/(ASCE)NH.1527-6996.0000336
SN  - 1527-6988
SN  - 1527-6996
VL  - 21
IS  - 1
PB  - American Society of Civil Engineers
CY  - Reston
ER  - 
TY  - JOUR
A1  - Baes, Marzieh
A1  - Sobolev, Stephan
A1  - Gerya, Taras V.
A1  - Brune, Sascha
T1  - Plume-induced subduction initiation
BT  - single-slab or multi-slab subduction?
JF  - Geochemistry, geophysics, geosystems
N2  - Initiation of subduction following the impingement of a hot buoyant mantle plume is one of the few scenarios that allow breaking the lithosphere and recycling a stagnant lid without requiring any preexisting weak zones. Here, we investigate factors controlling the number and shape of retreating subducting slabs formed by plume-lithosphere interaction. Using 3-D thermomechanical models we show that the deformation regime, which defines formation of single-slab or multi-slab subduction, depends on several parameters such as age of oceanic lithosphere, thickness of the crust and large-scale lithospheric extension rate. Our model results indicate that on present-day Earth multi-slab plume-induced subduction is initiated only if the oceanic lithosphere is relatively young (<30-40 Myr, but >10 Myr), and the crust has a typical thickness of 8 km. In turn, development of single-slab subduction is facilitated by older lithosphere and pre-imposed extensional stresses. In early Earth, plume-lithosphere interaction could have led to formation of either episodic short-lived circular subduction when the oceanic lithosphere was young or to multi-slab subduction when the lithosphere was old.
KW  - subduction zone
KW  - plume
KW  - numerical model
KW  - singleslab
KW  - multi-slab
Y1  - 2020
U6  - https://doi.org/10.1029/2019GC008663
SN  - 1525-2027
VL  - 21
IS  - 2
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Liu, Qi
A1  - Adler, Karsten
A1  - Lipus, Daniel
A1  - Kämpf, Horst
A1  - Bussert, Robert
A1  - Plessen, Birgit
A1  - Schulz, Hans-Martin
A1  - Krauze, Patryk
A1  - Horn, Fabian
A1  - Wagner, Dirk
A1  - Mangelsdorf, Kai
A1  - Alawi, Mashal
T1  - Microbial signatures in deep CO2-saturated miocene sediments of the active Hartousov mofette system (NW Czech Republic)
JF  - Frontiers in microbiology
N2  - The Hartousov mofette system is a natural CO2 degassing site in the central Cheb Basin (Eger Rift, Central Europe). In early 2016 a 108 m deep core was obtained from this system to investigate the impact of ascending mantle-derived CO2 on indigenous deep microbial communities and their surrounding life habitat. During drilling, a CO2 blow out occurred at a depth of 78.5 meter below surface (mbs) suggesting a CO2 reservoir associated with a deep low-permeable CO2-saturated saline aquifer at the transition from Early Miocene terrestrial to lacustrine sediments. Past microbial communities were investigated by hopanoids and glycerol dialkyl glycerol tetraethers (GDGTs) reflecting the environmental conditions during the time of deposition rather than showing a signal of the current deep biosphere. The composition and distribution of the deep microbial community potentially stimulated by the upward migration of CO2 starting during Mid Pleistocene time was investigated by intact polar lipids (IPLs), quantitative polymerase chain reaction (qPCR), and deoxyribonucleic acid (DNA) analysis. The deep biosphere is characterized by microorganisms that are linked to the distribution and migration of the ascending CO2-saturated groundwater and the availability of organic matter instead of being linked to single lithological units of the investigated rock profile. Our findings revealed high relative abundances of common soil and water bacteria, in particular the facultative, anaerobic and potential iron-oxidizing Acidovorax and other members of the family Comamonadaceae across the whole recovered core. The results also highlighted the frequent detection of the putative sulfate-oxidizing and CO2-fixating genus Sulfuricurvum at certain depths. A set of new IPLs are suggested to be indicative for microorganisms associated to CO2 accumulation in the mofette system.
KW  - geo-bio interaction
KW  - CO2
KW  - mofette systems
KW  - Eger Rift
KW  - microbial lipid
KW  - biomarker
KW  - microbial diversity
KW  - deep biosphere
KW  - saline groundwater
Y1  - 2020
U6  - https://doi.org/10.3389/fmicb.2020.543260
SN  - 1664-302X
VL  - 11
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Mogrovejo Arias, Diana Carolina
A1  - Brill, Florian H. H.
A1  - Wagner, Dirk
T1  - Potentially pathogenic bacteria isolated from diverse habitats in Spitsbergen, Svalbard
JF  - Environmental earth sciences
N2  - The Arctic ecosystem, a reservoir of genetic microbial diversity, represents a virtually unlimited source of microorganisms that could interact with human beings. Despite continuous exploration of Arctic habitats and description of their microbial communities, bacterial phenotypes commonly associated with pathogenicity, such as hemolytic activity, have rarely been reported. In this study, samples of snow, fresh and marine water, soil, and sediment from several habitats in the Arctic archipelago of Svalbard were collected during Summer, 2017. Bacterial isolates were obtained after incubation on oligotrophic media at different temperatures and their hemolytic potential was assessed on sheep blood agar plates. Partial (alpha) or true (beta) hemolysis was observed in 32 out of 78 bacterial species. Genes expressing cytolytic compounds, such as hemolysins, likely increase the general fitness of the producing microorganisms and confer a competitive advantage over the availability of nutrients in natural habitats. In environmental species, the nutrient-acquisition function of these compounds presumably precedes their function as toxins for mammalian erythrocytes. However, in the light of global warming, the presence of hemolytic bacteria in Arctic environments highlights the possible risks associated with these microorganisms in the event of habitat melting/destruction, ecosystem transition, and re-colonization.
KW  - Arctic
KW  - Svalbard
KW  - hemolysins
KW  - climate change
KW  - pathogens
KW  - virulence
Y1  - 2020
U6  - https://doi.org/10.1007/s12665-020-8853-4
SN  - 1866-6280
SN  - 1866-6299
VL  - 79
IS  - 5
PB  - Springer
CY  - Berlin ; Heidelberg
ER  - 
TY  - JOUR
A1  - Niemz, Peter
A1  - Cesca, Simone
A1  - Heimann, Sebastian
A1  - Grigoli, Francesco
A1  - von Specht, Sebastian
A1  - Hammer, Conny
A1  - Zang, Arno
A1  - Dahm, Torsten
T1  - Full-waveform-based characterization of acoustic emission activity in a mine-scale experiment
BT  - a comparison of conventional and advanced hydraulic fracturing schemes
JF  - Geophysical journal international / the Royal Astronomical Society, the Deutsche Geophysikalische Gesellschaft and the European Geophysical Society
N2  - Understanding fracturing processes and the hydromechanical relation to induced seismicity is a key question for enhanced geothermal systems (EGS). Commonly massive fluid injection, predominately causing hydroshearing, are used in large-scale EGS but also hydraulic fracturing approaches were discussed. To evaluate the applicability of hydraulic fracturing techniques in EGS, six in situ, multistage hydraulic fracturing experiments with three different injection schemes were performed under controlled conditions in crystalline rock at the Aspo Hard Rock Laboratory (Sweden). During the experiments the near-field ground motion was continuously recorded by 11 piezoelectric borehole sensors with a sampling rate of 1 MHz. The sensor network covered a volume of 30x30x30 m around a horizontal, 28-m-long injection borehole at a depth of 410 m. To extract and characterize massive, induced, high-frequency acoustic emission (AE) activity from continuous recordings, a semi-automated workflow was developed relying on full waveform based detection, classification and location procedures. The approach extended the AE catalogue from 196 triggered events in previous studies to more than 19600 located AEs. The enhanced catalogue, for the first time, allows a detailed analysis of induced seismicity during single hydraulic fracturing experiments, including the individual fracturing stages and the comparison between injection schemes. Beside the detailed study of the spatio-temporal patterns, event clusters and the growth of seismic clouds, we estimate relative magnitudes and b-values of AEs for conventional, cyclic progressive and dynamic pulse injection schemes, the latter two being fatigue hydraulic fracturing techniques. While the conventional fracturing leads to AE patterns clustered in planar regions, indicating the generation of a single main fracture plane, the cyclic progressive injection scheme results in a more diffuse, cloud-like AE distribution, indicating the activation of a more complex fracture network. For a given amount of hydraulic energy (pressure multiplied by injected volume) pumped into the system, the cyclic progressive scheme is characterized by a lower rate of seismicity, lower maximum magnitudes and significantly larger b-values, implying an increased number of small events relative to the large ones. To our knowledge, this is the first direct comparison of high resolution seismicity in a mine-scale experiment induced by different hydraulic fracturing schemes.
KW  - Fracture and flow
KW  - Spatial analysis
KW  - Statistical methods
KW  - Time-series analysis
KW  - Induced seismicity
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa127
SN  - 0955-419X
SN  - 1365-246X
VL  - 222
IS  - 1
SP  - 189
EP  - 206
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Wang, Lei
A1  - Dresen, Georg
A1  - Rybacki, Erik
A1  - Bonnelye, Audrey
A1  - Bohnhoff, Marco
T1  - Pressure-dependent bulk compressibility of a porous granular material modeled by improved contact mechanics and micromechanical approaches
BT  - effects of surface roughness of grains
JF  - Acta materialia
N2  - The change of the mechanical properties of granular materials with pressure is an important topic associated with many industrial applications. In this paper we investigate the influence of hydrostatic pressure (P-e) on the effective bulk compressibility (C-eff) of a granular material by applying two modified theoretical approaches that are based on contact mechanics and micromechanics, respectively. For a granular material composed of rough grains, an extended contact model is developed to elucidate the effect of roughness of grain surfaces on bulk compressibility. At relatively low pressures, the model predicts that the decrease of bulk compressibility with pressure may be described by a power law with an exponent of -1/2 (i.e., C-eff proportional to P-e(1/2) ), but deviates at intermediate pressures. At elevated pressures beyond full contact, bulk compressibility remains almost unchanged, which may be roughly evaluated by continuum contact mechanics. As an alternative explanation of pressure-dependent bulk compressibility, we suggest a micromechanical model that accounts for effects of different types of pore space present in granular materials. Narrow and compliant inter-granular cracks are approximated by three-dimensional oblate spheroidal cracks with rough surfaces, whereas the equant and stiff pores surrounded by three and four neighboring grains are modeled as tubular pores with cross sections of three and four cusp-like corners, respectively. In this model, bulk compressibility is strongly reduced with increasing pressure by progressive closure of rough-walled cracks. At pressures exceeding crack closure pressure, deformation of the remaining equant pores is largely insensitive to pressure, with almost no further change in bulk compressibility. To validate these models, we performed hydrostatic compression tests on Bentheim sandstone (a granular rock consisting of quartz with high porosity) under a wide range of pressure. The relation between observed microstructures and measured pressure-dependent bulk compressibility is well explained by both suggested models.
KW  - Bulk compressibility
KW  - Granular materials
KW  - Roughness
KW  - Micromechanical model
KW  - Contact model
Y1  - 2020
U6  - https://doi.org/10.1016/j.actamat.2020.01.063
SN  - 1359-6454
SN  - 1873-2453
VL  - 188
SP  - 259
EP  - 272
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Pradhan, Prajal
A1  - Kriewald, Steffen
A1  - Costa, Luís Fílípe Carvalho da
A1  - Rybski, Diego
A1  - Benton, Tim G.
A1  - Fischer, Günther
A1  - Kropp, Jürgen
T1  - Urban food systems: how regionalization can contribute to climate change mitigation
JF  - Environmental science & technology
N2  - Cities will play a key role in the grand challenge of nourishing a growing global population, because, due to their population density, they set the demand. To ensure that food systems are sustainable, as well as nourishing, one solution often suggested is to shorten their supply chains toward a regional rather than a global basis. While such regional systems may have a range of costs and benefits, we investigate the mitigation potential of regionalized urban food systems by examining the greenhouse gas emissions associated with food transport. Using data on food consumption for 7108 urban administrative units (UAUs), we simulate total transport emissions for both regionalized and globalized supply chains. In regionalized systems, the UAUs' demands are fulfilled by peripheral food production, whereas to simulate global supply chains, food demand is met from an international pool (where the origin can be any location globally). We estimate that regionalized systems could reduce current emissions from food transport. However, because longer supply chains benefit from maximizing comparative advantage, this emission reduction would require closing yield gaps, reducing food waste, shifting toward diversified farming, and consuming seasonal produce. Regionalization of food systems will be an essential component to limit global warming to well below 2 degrees C in the future.
Y1  - 2020
U6  - https://doi.org/10.1021/acs.est.0c02739
SN  - 0013-936X
SN  - 1520-5851
VL  - 54
IS  - 17
SP  - 10551
EP  - 10560
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schönfeldt, Elisabeth
A1  - Pánek, Tomáš
A1  - Winocur, Diego
A1  - Silhan, Karel
A1  - Korup, Oliver
T1  - Postglacial Patagonian mass movement
BT  - from rotational slides and spreads to earthflows
JF  - Geomorphology : an international journal on pure and applied geomorphology
N2  - Many of the volcanic plateau margins of the eastern, formerly glaciated, foreland of the Patagonian Andes are undermined by giant landslides (>= 10(8) m(3)). One cluster of such landslides extends along the margin of the Meseta del Lago Buenos Aires (MLBA) plateau that is formed mainly by Neogene-Quaternary basalts. The dry climate is at odds with numerous >2-km long earthflows nested within older and larger compound landslides. We present a hydrological analysis, a detailed geomorphic map, interpretations of exposed landslide interiors, and radiocarbon dating of the El Mirador landslide, which is one of the largest and morphologically most representative landslide. We find that the presence of lakes on top of the plateau, causing low infiltration rates, correlates negatively with the abundance of earthflows on compound landslides along the plateau margins. Field outcrops show that the pattern of compound landslides and earthflows is likely controlled by groundwater seepage at the contact between the basalts and underlying soft Miocene molasse. Numerous peat bogs store water and sediment and are more abundant in earthflow-affected areas than in their contributing catchment areas. <br /> Radiocarbon dates indicate that these earthflows displaced metre-thick layers of peat in the late Holocene (<2.5 ka). We conclude that earthflows of the MLBA plateau might be promising proxies of past hydroclimatic conditions in the Patagonian foreland, if strong earthquakes or gradual crustal stress changes due to glacioisostatic rebound can be ruled out.
KW  - landslide
KW  - lateral spread
KW  - earthflow
KW  - Patagonia
Y1  - 2020
U6  - https://doi.org/10.1016/j.geomorph.2020.107316
SN  - 0169-555X
SN  - 1872-695X
VL  - 367
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Scherler, Dirk
A1  - Schwanghart, Wolfgang
T1  - Drainage divide networks
BT  - Part 2: Response to perturbations
JF  - Earth surface dynamics
N2  - Drainage divides are organized into tree-like networks that may record information about drainage divide mobility. However, views diverge about how to best assess divide mobility. Here, we apply a new approach of automatically extracting and ordering drainage divide networks from digital elevation models to results from landscape evolution model experiments. We compared landscapes perturbed by strike-slip faulting and spatiotemporal variations in erodibility to a reference model to assess which topographic metrics (hillslope relief, flow distance, and chi) are diagnostic of divide mobility. Results show that divide segments that are a minimum distance of similar to 5 km from river confluences strive to attain constant values of hillslope relief and flow distance to the nearest stream. Disruptions of such patterns can be related to mobile divides that are lower than stable divides, closer to streams, and often asymmetric in shape. In general, we observe that drainage divides high up in the network, i.e., at great distances from river confluences, are more susceptible to disruptions than divides closer to these confluences and are thus more likely to record disturbance for a longer time period. We found that across-divide differences in hillslope relief proved more useful for assessing divide migration than other tested metrics. However, even stable drainage divide networks exhibit across-divide differences in any of the studied topographic metrics. Finally, we propose a new metric to quantify the connectivity of divide junctions.
KW  - dynamics
KW  - landscape evolution
KW  - low-relief
KW  - patterns
KW  - river
KW  - scale
KW  - tectonics
Y1  - 2020
U6  - https://doi.org/10.5194/esurf-8-261-2020
SN  - 2196-6311
SN  - 2196-632X
VL  - 8
IS  - 2
SP  - 261
EP  - 274
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Esfahani, Reza Dokht Dolatabadi
A1  - Gholami, Ali
A1  - Ohrnberger, Matthias
T1  - An inexact augmented Lagrangian method for nonlinear dispersion-curve inversion using Dix-type global linear approximation
JF  - Geophysics
N2  - Dispersion-curve inversion of Rayleigh waves to infer subsurface shear-wave velocity is a long-standing problem in seismology. Due to nonlinearity and ill-posedness, sophisticated regularization techniques are required to solve the problem for a stable velocity model. We have formulated the problem as a minimization problem with nonlinear operator constraint and then solve it by using an inexact augmented Lagrangian method, taking advantage of the Haney-Tsai Dix-type relation (a global linear approximation of the nonlinear forward operator). This replaces the original regularized nonlinear problem with iterative minimization of a more tractable regularized linear problem followed by a nonlinear update of the phase velocity (data) in which the update can be performed accurately with any forward modeling engine, for example, the finite-element method. The algorithm allows discretizing the medium with thin layers (for the finite-element method) and thus omitting the layer thicknesses from the unknowns and also allows incorporating arbitrary regularizations to shape the desired velocity model. In this research, we use total variation regularization to retrieve the shear-wave velocity model. We use two synthetic and two real data examples to illustrate the performance of the inversion algorithm with total variation regularization. We find that the method is fast and stable, and it converges to the solution of the original nonlinear problem.
Y1  - 2020
U6  - https://doi.org/10.1190/GEO2019-0717.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 85
IS  - 5
SP  - EN77
EP  - EN85
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Sieber, Melanie Jutta
A1  - Brink, Frank J.
A1  - Leys, Clyde
A1  - King, Penelope L.
A1  - Henley, Richard W.
T1  - Prograde and retrograde metasomatic reactions in mineralised magnesium- silicate skarn in the Cu-Au Ertsberg East Skarn System, Ertsberg, Papua Province, Indonesia
JF  - Ore geology reviews
N2  - The 2.7-2.9 Ma Ertsberg East Skarn System (EESS) is a world-class Cu-Au skarn that formed within and adjacent to an intrusion within a paleodepth of 0.5 km and > 2.5 km. Its economic mineralisation developed by sustained reaction of magmatic fluid with contact metamorphosed siliciclastic and carbonate rocks at the margin of the adjacent Ertsberg quartz monzodiorite intrusion. Based on high-resolution mineral mapping, chemical analysis and thermodynamic calculations, the multistage formation processes of the exoskarn components of the EESS are examined in the context of changing pressure, temperature, fluid composition and fluid phase. We show that contact metamorphism of dolomitic sediments occurred at 51 +/- 5 MPa, between 700 degrees C and 800 degrees C and in the presence of a H2O-CO2-fluid containing similar to 10 to similar to 70 mol% CO2. This prograde metamorphism formed a forsterite + diopside + calcite + phlogopite + spinel assemblage. Such forsterite-dominated skarns account for similar to 55 vol% of the EESS exoskarns. Rare pargasite (previously unrecognized in this deposit) formed locally in the metamorphosed carbonate sequence where the protolith was composed of supratidal evaporites with dolomitic carbonate and interlayered calc-silicate rocks. The subsequent flux of a lower pressure magmatic gas containing SO2(g) caused sulphate metasomatism. This high temperature gas alteration of the metamorphic assemblage also caused skarn Cu-Fe-sulphide mineralisation. The influx of a SO2 gas through fracture permeability occurred at a temperature between similar to 600 and 700 degrees C and caused calcite to be replaced by anhydrite, with the coupled release of H2S(g). This in-situ release of H2S(g) scavenged trace Cu from the gas phase to deposit Cu-Fe-sulphides, which make the economic value of the distinct. We demonstrate that the formation of metal sulphides within forsterite skarns of the Ertsberg East Skarn System required a minimum flux of similar to 1,050 Mt SO2(g) and show that volcanic degassing may have occurred over a time span of similar to 3,900 years. As the system waned, the ambient fluid resulted in partial retrograde serpentinization of olivine and diopside without carbonation, and at temperatures sufficiently high to preserve anhydrite.
KW  - porphyry Cu-Au deposit
KW  - magnesium silicate skarn
KW  - pargasite
KW  - gas-solid
KW  - reaction
KW  - sulphate metasomatism
Y1  - 2020
U6  - https://doi.org/10.1016/j.oregeorev.2020.103697
SN  - 0169-1368
SN  - 1872-7360
VL  - 125
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Zhang, Xiaolin
A1  - Yang, Xiaoqiang
A1  - Jomaa, Seifeddine
A1  - Rode, Michael
T1  - Analyzing impacts of seasonality and landscape gradient on event-scale nitrate-discharge dynamics based on nested high-frequency monitoring
JF  - Journal of hydrology
N2  - Increasingly available high-frequency data during storm events, when hydrological dynamics most likely activate nitrate storage-flux exchanges, reveal insights into catchment nitrate dynamics. In this study, we explored impacts of seasonality and landscape gradients on nitrate concentration-discharge (C-Q) hysteresis patterns in the Selke catchment, central Germany, which has heterogeneous combinations of meteorological, hydrogeological and land use conditions. Three nested gauging stations established along the main Selke River captured flow and nitrate export dynamics from the uppermost subcatchment (mixed forest and arable land), middle subcatchment (pure steep forest) and lowermost subcatchment (arable and urban land). We collected continuous high-frequency (15-min) discharge and nitrate concentration data from 2012 to 2017 and analyzed the 223 events detected at all three stations. A dominant hysteresis pattern in the uppermost and middle subcatchments was counter-clockwise and combined with an accretion effect, indicating many proximal and mobilized distal nitrate sources. However, 66% of all events at the catchment outlet experienced a dilution effect, possibly due to mechanisms that vary seasonally. During wetting/wet periods (October-March), it was combined mainly with a counter-clockwise pattern due to the dominance of event runoff volume from the uppermost and middle subcatchments. During drying/dry periods (April-September), however, it was combined mainly with a clockwise pattern due to occasional quick surface flows from lowland near-stream urban areas. In addition, the clockwise hysteresis occurred mainly from May-October during mostly drying/dry periods at all three sites, indicating little distal nitrate transport in response to the low terrestrial hydrological connectivity, especially in the lowermost dry and flat sub-catchment. This comprehensive analysis (i.e., clockwise vs. counter-clockwise, accretion vs. dilution) enables in-depth analysis of nitrate export mechanisms during certain periods under different landscape conditions. Specific combination of C-Q relationships could identify target locations for agricultural management actions that decrease nitrate output. Therefore, we strongly encourage long-term multisite and high-frequency monitoring strategies in heterogeneous nested catchment(s), which can help understand process mechanisms, generate data for physical-based water-quality modeling and provide guidance for water and agricultural management.
KW  - nitrate export dynamic
KW  - C-Q relationship
KW  - hysteresis pattern
KW  - high-frequency data
KW  - landscape effect
KW  - seasonality effect
Y1  - 2020
U6  - https://doi.org/10.1016/j.jhydrol.2020.125585
SN  - 0022-1694
SN  - 1879-2707
VL  - 591
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Albrecht, Torsten
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Glacial-cycle simulations of the Antarctic Ice Sheet with the Parallel Ice Sheet Model (PISM)
BT  - Part 1: boundary conditions and climatic forcing
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Simulations of the glacial-interglacial history of the Antarctic Ice Sheet provide insights into dynamic threshold behavior and estimates of the ice sheet's contributions to global sea-level changes for the past, present and future. However, boundary conditions are weakly constrained, in particular at the interface of the ice sheet and the bedrock. Also climatic forcing covering the last glacial cycles is uncertain, as it is based on sparse proxy data. <br /> We use the Parallel Ice Sheet Model (PISM) to investigate the dynamic effects of different choices of input data, e.g., for modern basal heat flux or reconstructions of past changes of sea level and surface temperature. As computational resources are limited, glacial-cycle simulations are performed using a comparably coarse model grid of 16 km and various parameterizations, e.g., for basal sliding, iceberg calving, or for past variations in precipitation and ocean temperatures. In this study we evaluate the model's transient sensitivity to corresponding parameter choices and to different boundary conditions over the last two glacial cycles and provide estimates of involved uncertainties. We also discuss isolated and combined effects of climate and sea-level forcing. Hence, this study serves as a "cookbook" for the growing community of PISM users and paleo-ice sheet modelers in general. <br /> For each of the different model uncertainties with regard to climatic forcing, ice and Earth dynamics, and basal processes, we select one representative model parameter that captures relevant uncertainties and motivates corresponding parameter ranges that bound the observed ice volume at present. The four selected parameters are systematically varied in a parameter ensemble analysis, which is described in a companion paper.
Y1  - 2020
U6  - https://doi.org/10.5194/tc-14-599-2020
SN  - 1994-0416
SN  - 1994-0424
VL  - 14
IS  - 2
SP  - 599
EP  - 632
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Figueroa Villegas, Sara
A1  - Weiss, Jonathan R.
A1  - Hongn, Fernando D.
A1  - Pingel, Heiko
A1  - Escalante, Leonardo
A1  - Elías, Leonardo
A1  - Aranda-Viana, R. Germán
A1  - Strecker, Manfred
T1  - Late pleistocene to recent deformation in the thick-skinned fold-and-thrust belt of Northwestern Argentina (Central Calchaqui Valley, 26 degrees S)
JF  - Tectonics / American Geophysical Union, AGU ; European Geophysical Society, EGS
N2  - The thick-skinned fold-and-thrust belt on the eastern flank of the Andean Plateau in northwestern Argentina (NWA) is a zone of active contractional deformation characterized by fault-bounded mountain ranges with no systematic spatiotemporal pattern of tectonic activity. In contrast, the thin-skinned Subandean fold-and-thrust belt of northern Argentina and southern Bolivia is characterized primarily by in-sequence (i.e., west to east) fault progression, with a narrow zone of Quaternary deformation focused at the front of the orogenic wedge. To better understand how recent deformation is accommodated across these mountain ranges and the Argentinian portion of the orogen in particular, estimating and comparing deformation rates and patterns across different timescales is essential. We present Late Pleistocene shortening rates for the central Calchaqui intermontane valley in NWA associated with at least three episodes of deformation. Global Positioning System data for the same region reveal a gradual decrease in horizontal surface velocities from the Eastern Cordillera toward the foreland, which contrasts with the rapid velocity gradient associated with a locked decollement in the Subandean Ranges of southern Bolivia. Our new results represent a small view of regional deformation that, when considered in combination with the shallow crustal seismicity and decadal-scale surface velocities, support the notion that strain release in NWA is associated with numerous slowly deforming structures that are distributed throughout the orogen.
Y1  - 2020
U6  - https://doi.org/10.1029/2020TC006394
SN  - 0278-7407
SN  - 1944-9194
VL  - 40
IS  - 1
PB  - American Geophysical Union
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Wetzel, Maria
A1  - Kempka, Thomas
A1  - Kühn, Michael
T1  - Hydraulic and mechanical impacts of pore space alterations within a sandstone quantified by a flow velocity-dependent precipitation approach
JF  - Materials
N2  - Geochemical processes change the microstructure of rocks and thereby affect their physical behaviour at the macro scale. A micro-computer tomography (micro-CT) scan of a typical reservoir sandstone is used to numerically examine the impact of three spatial alteration patterns on pore morphology, permeability and elastic moduli by correlating precipitation with the local flow velocity magnitude. The results demonstrate that the location of mineral growth strongly affects the permeability decrease with variations by up to four orders in magnitude. Precipitation in regions of high flow velocities is characterised by a predominant clogging of pore throats and a drastic permeability reduction, which can be roughly described by the power law relation with an exponent of 20. A continuous alteration of the pore structure by uniform mineral growth reduces the permeability comparable to the power law with an exponent of four or the Kozeny-Carman relation. Preferential precipitation in regions of low flow velocities predominantly affects smaller throats and pores with a minor impact on the flow regime, where the permeability decrease is considerably below that calculated by the power law with an exponent of two. Despite their complete distinctive impact on hydraulics, the spatial precipitation patterns only slightly affect the increase in elastic rock properties with differences by up to 6.3% between the investigated scenarios. Hence, an adequate characterisation of the spatial precipitation pattern is crucial to quantify changes in hydraulic rock properties, whereas the present study shows that its impact on elastic rock parameters is limited. The calculated relations between porosity and permeability, as well as elastic moduli can be applied for upscaling micro-scale findings to reservoir-scale models to improve their predictive capabilities, what is of paramount importance for a sustainable utilisation of the geological subsurface.
KW  - Bentheim sandstone
KW  - digital rock physics
KW  - micro-CT
KW  - elastic properties
KW  - permeability
KW  - precipitation
Y1  - 2020
U6  - https://doi.org/10.3390/ma13143100
SN  - 1996-1944
VL  - 13
IS  - 14
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Cheng, Chaojie
A1  - Milsch, Harald
T1  - Evolution of fracture aperture in quartz sandstone under hydrothermal conditions
BT  - mechanical and chemical effects
JF  - Minerals
N2  - Fractures efficiently affect fluid flow in geological formations, and thereby determine mass and energy transport in reservoirs, which are not least exploited for economic resources. In this context, their response to mechanical and thermal changes, as well as fluid-rock interactions, is of paramount importance. In this study, a two-stage flow-through experiment was conducted on a pure quartz sandstone core of low matrix permeability, containing one single macroscopic tensile fracture. In the first short-term stage, the effects of mechanical and hydraulic aperture on pressure and temperature cycles were investigated. The purpose of the subsequent intermittent-flow long-term (140 days) stage was to constrain the evolution of the geometrical and hydraulic fracture properties resulting from pressure solution. Deionized water was used as the pore fluid, and permeability, as well as the effluent Si concentrations, were systematically measured. Overall, hydraulic aperture was shown to be significantly less affected by pressure, temperature and time, in comparison to mechanical aperture. During the long-term part of the experiment at 140 degrees C, the effluent Si concentrations likely reached a chemical equilibrium state within less than 8 days of stagnant flow, and exceeded the corresponding hydrostatic quartz solubility at this temperature. This implies that the pressure solution was active at the contacting fracture asperities, both at 140 degrees C and after cooling to 33 degrees C. The higher temperature yielded a higher dissolution rate and, consequently, a faster attainment of chemical equilibrium within the contact fluid. X-ray mu CT observations evidenced a noticeable increase in fracture contact area ratio, which, in combination with theoretical considerations, implies a significant decrease in mechanical aperture. In contrast, the sample permeability, and thus the hydraulic fracture aperture, virtually did not vary. In conclusion, pressure solution-induced fracture aperture changes are affected by the degree of time-dependent variations in pore fluid composition. In contrast to the present case of a quasi-closed system with mostly stagnant flow, in an open system with continuous once-through fluid flow, the activity of the pressure solution may be amplified due to the persistent fluid-chemical nonequilibrium state, thus possibly enhancing aperture and fracture permeability changes.
KW  - flow-through experiment
KW  - fracture aperture
KW  - pressure solution
KW  - mass
KW  - transfer
KW  - silica concentration
KW  - permeability
KW  - quartz sandstone
Y1  - 2020
U6  - https://doi.org/10.3390/min10080657
SN  - 2075-163X
VL  - 10
IS  - 8
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Cook, Kristen L.
A1  - Turowski, Jens M.
A1  - Hovius, Niels
T1  - Width control on event-scale deposition and evacuation of sediment in bedrock-confined channels
JF  - Earth surface processes and landforms : the journal of the British Geomorphological Research Group
N2  - In mixed bedrock-alluvial rivers, the response of the system to a flood event can be affected by a number of factors, including coarse sediment availability in the channel, sediment supply from the hillslopes and upstream, flood sequencing and coarse sediment grain size distribution. However, the impact of along-stream changes in channel width on bedload transport dynamics remains largely unexplored. We combine field data, theory and numerical modelling to address this gap. First, we present observations from the Daan River gorge in western Taiwan, where the river flows through a 1 km long 20-50 m wide bedrock gorge bounded upstream and downstream by wide braidplains. We documented two flood events during which coarse sediment evacuation and redeposition appear to cause changes of up to several metres in channel bed elevation. Motivated by this case study, we examined the relationships between discharge, channel width and bedload transport capacity, and show that for a given slope narrow channels transport bedload more efficiently than wide ones at low discharges, whereas wider channels are more efficient at high discharges. We used the model sedFlow to explore this effect, running a random sequence of floods through a channel with a narrow gorge section bounded upstream and downstream by wider reaches. Channel response to imposed floods is complex, as high and low discharges drive different spatial patterns of erosion and deposition, and the channel may experience both of these regimes during the peak and recession periods of each flood. Our modelling suggests that width differences alone can drive substantial variations in sediment flux and bed response, without the need for variations in sediment supply or mobility. The fluctuations in sediment transport rates that result from width variations can lead to intermittent bed exposure, driving incision in different segments of the channel during different portions of the hydrograph.
KW  - bedload transport
KW  - discharge variability
KW  - bedrock-alluvial channels
KW  - channel width
KW  - hysteresis
Y1  - 2020
U6  - https://doi.org/10.1002/esp.4993
SN  - 0197-9337
SN  - 1096-9837
VL  - 45
IS  - 14
SP  - 3702
EP  - 3713
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Wieczorek, Mareike
A1  - Herzschuh, Ulrike
T1  - Compilation of relative pollen productivity (RPP) estimates and taxonomically harmonised RPP datasets for single continents and Northern Hemisphere extratropics
JF  - Earth system science data : ESSD
N2  - Relative pollen productivity (RPP) estimates are fractionate values, often in relation to Poaceae, that allow vegetation cover to be estimated from pollen counts with the help of models. RPP estimates are especially used in the scientific community in Europe and China, with a few studies in North America. Here we present a comprehensive compilation of available northern hemispheric RPP studies and their results arising from 51 publications with 60 sites and 131 taxa. This compilation allows scientists to identify data gaps in need of further RPP analyses but can also aid them in finding an RPP set for their study region. We also present a taxonomically harmonised, unified RPP dataset for the Northern Hemisphere and subsets for North America (including Greenland), Europe (including arctic Russia), and China, which we generated from the available studies. The unified dataset gives the mean RPP for 55 harmonised taxa as well as fall speeds, which are necessary to reconstruct vegetation cover from pollen counts and RPP values. Data are openly available at https://doi.org/10.1594/PANGAEA.922661 (Wieczorek and Herzschuh, 2020).
Y1  - 2020
U6  - https://doi.org/10.5194/essd-12-3515-2020
SN  - 1866-3508
SN  - 1866-3516
VL  - 12
IS  - 4
SP  - 3515
EP  - 3528
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Heeschen, Katja U.
A1  - Janocha, Julian
A1  - Spangenberg, Erik
A1  - Schicks, Judith Maria
A1  - Giese, Ronny
T1  - The impact of ice on the tensile strength of unconsolidated sand
BT  - a model for gas hydrate-bearing sands?
JF  - Marine and petroleum geology
N2  - Tensile strength is an important parameter when it comes to predictions of potential fracturing of sediments by natural processes such as the emplacement of ice or gas hydrate lenses, as well as anthropogenic fracturing or else the stability of engineering constructions such as boreholes. Yet, tensile strength (sigma(tau)) measurements of unconsolidated ice-bearing or gas hydrate-bearing sands are scarce and affected by a large variability. <br /> In the course of the SUGAR project we successfully used ice as a model for pore-filling and "load-bearing" gas hydrate in sand to determine compressional wave velocity. We were thus able to verify comparable formation characteristics and morphologies of ice and gas hydrate within the pore space. As these are important values for the tensile strength of ice/hydrate-bearing sands, ice was also used as a model for hydrate-bearing sands, despite differences in the mechanical behavior and strength of pure ice and gas hydrate. Water-saturated sand cores with ice saturations (S-ice) between 0 and 100% were tested at -6.8 degrees C. The varying S-ice were a result of the freezing point depression caused by saline solutions of different concentrations. The sigma(tau) was directly determined using a sleeve-fracturing test with an internal pressure that was created within the frozen samples. The setup was also adapted to fit a pressure vessel for tests using confining pressure. <br /> The correlation of S-ice - sigma(tau) shows an exponential increase of sigma(tau) with S-ice. Whereas at S-ice < 60% the increase is small, it is large at S-ice > 80%. In conjunction with the change in strength, the viscoelastic behavior changes. A clear peak strength occurs at S-ice > 80%. We conclude that given 60% < S-ice < 80% the pore-filling morphology of the ice converts into a frame-building habitus and at S-ice > 80% the frame gains strength while the amount of residual water decreases. Tensile failure and cracking now exceed grain boundary sliding as the prevailing failure mode. The ice morphology in the sand is non-cementing and comparable to a gas hydrate-sand mixture.
KW  - tensile strength
KW  - ice-grain mixture
KW  - gas hydrate
KW  - saline permafrost
KW  - ice
KW  - frozen soil
Y1  - 2020
U6  - https://doi.org/10.1016/j.marpetgeo.2020.104607
SN  - 0264-8172
SN  - 1873-4073
VL  - 122
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Weatherill, Graeme
A1  - Kotha, Sreeram Reddy
A1  - Cotton, Fabrice
T1  - Re-thinking site amplification in regional seismic risk assessment
JF  - Earthquake spectra : the professional journal of the Earthquake Engineering Research Institute
N2  - Probabilistic assessment of seismic hazard and risk over a geographical region presents the modeler with challenges in the characterization of the site amplification that are not present in site-specific assessment. Using site-to-site residuals from a ground motion model fit to observations from the Japanese KiK-net database, correlations between measured local amplifications and mappable proxies such as topographic slope and geology are explored. These are used subsequently to develop empirical models describing amplification as a direct function of slope, conditional upon geological period. These correlations also demonstrate the limitations of inferring 30-m shearwave velocity from slope and applying them directly into ground motion models. Instead, they illustrate the feasibility of deriving spectral acceleration amplification factors directly from sets of observed records, which are calibrated to parameters that can be mapped uniformly on a regional scale. The result is a geologically calibrated amplification model that can be incorporated into national and regional seismic hazard and risk assessment, ensuring that the corresponding total aleatory variability reflects the predictive capability of the mapped site proxy.
KW  - earthquake hazard analysis
KW  - ground motion
KW  - seismic risk
KW  - site effects
KW  - regional mapping
Y1  - 2020
U6  - https://doi.org/10.1177/8755293019899956
SN  - 8755-2930
SN  - 1944-8201
VL  - 36
IS  - 1_SUPPL
SP  - 274
EP  - 297
PB  - Sage Publishing
CY  - Thousand Oaks, CA
ER  - 
TY  - JOUR
A1  - Putra, Muhammad Panji Islam Fajar
A1  - Pradhan, Prajal
A1  - Kropp, Jürgen
T1  - A systematic analysis of Water-Energy-Food security nexus
BT  - a South Asian case study
JF  - The science of the total environment : an international journal for scientific research into the environment and its relationship with man
N2  - Most South Asian countries have challenges in ensuring water, energy, and food (WEF) security, which are often interacting positively or negatively. To address these challenges, the nexus approach provides a framework to identify the interactions of the WEF sectors as an integrated system. However, most nexus studies only qualitatively discuss the interactions between these sectors. This study conducts a systematic analysis of the WEF security nexus in South Asia by using open data sources at the country scale. We analyze interactions between the WEF sectors statistically, defining positive and negative correlations between the WEF security indicators as synergies and trade-offs, respectively. By creating networks of the synergies and trade-offs, we further identify most positively and negatively influencing indicators in the WEF security nexus. We observe a larger share of trade-offs than synergies within the water and energy sectors and a larger share of synergies than trade-offs among the WEF sectors for South Asia. However, these observations vary across the South Asian countries. Our analysis highlights that strategies on promoting sustainable energy and discouraging fossil fuel use could have overall positive effects on the WEF security nexus in the countries. This study provides evidence for considering the WEF security nexus as an integrated system rather than just a combination of three different sectors or securities.
KW  - water security
KW  - food security
KW  - energy security
KW  - network analysis
KW  - water-energy-food nexus
KW  - sustainable development
Y1  - 2020
U6  - https://doi.org/10.1016/j.scitotenv.2020.138451
SN  - 0048-9697
SN  - 1879-1026
VL  - 728
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Specht, Sebastian von
T1  - ICBM Integrated Combined Baseline Modification
BT  - an algorithm for segmented baseline estimation
JF  - Seismological research letters
N2  - Accelerograms are the primary source for characterizing strong ground motion. It is therefore of paramount interest to have high-quality recordings free from any nonphysical contamination. Frequently, accelerograms are affected by baseline jumps and drifts, either related to the instrument and/or a major earthquake. In this work, I propose a correction method for these undesired baseline drifts based on segmented linear least squares. The algorithm operates on the integrated waveforms and combines all three instrument components to estimate a model that modifies the baseline to be at zero continuously. The procedure consists of two steps: first a suite of models with variable numbers of discontinuities is derived for all three instrument components. During this process, the number of discontinuities is reduced in a parsimonious way, for example, two very close discontinuities are merged into a single one. In the second step, the optimal model is selected on the basis of the Bayesian information criterion. I exemplify the application on synthetic waveforms with known discontinuities and on observed waveforms from a unified strong-motion database of the Japan Meteorological Agency (JMA) and the National Research Institute for Earth Science and Disaster Prevention (NIED, Japan) networks for the major events of the 2016 Kumamoto earthquakes. After the baseline jump correction, the waveforms are furthermore corrected for displacement according to Wang et al.(2011). The resulting displacements are comparable to the Interferometric Synthetic Aperture Radar-derived displacement estimates for the Kumamoto earthquake sequence.
Y1  - 2019
U6  - https://doi.org/10.1785/0220190134
SN  - 0895-0695
SN  - 1938-2057
VL  - 91
IS  - 1
SP  - 475
EP  - 487
PB  - Seismological Society of America, Eastern Section
CY  - Boulder, Colo.
ER  - 
TY  - JOUR
A1  - Karamzadeh Toularoud, Nasim
A1  - Heimann, Sebastian
A1  - Dahm, Torsten
A1  - Krüger, Frank
T1  - Earthquake source arrays
BT  - optimal configuration and applications in crustal structure studies
JF  - Geophysical journal international
N2  - A collection of earthquake sources recorded at a single station, under specific conditions, are considered as a source array (SA), that is interpreted as if earthquake sources originate at the station location and are recorded at the source location. Then, array processing methods, that is array beamforming, are applicable to analyse the recorded signals. A possible application is to use source array multiple event techniques to locate and characterize near-source scatterers and structural interfaces. In this work the aim is to facilitate the use of earthquake source arrays by presenting an automatic search algorithm to configure the source array elements. We developed a procedure to search for an optimal source array element distribution given an earthquake catalogue including accurate origin time and hypocentre locations. The objective function of the optimization process can be flexibly defined for each application to ensure the prerequisites (criteria) of making a source array. We formulated four quantitative criteria as subfunctions and used the weighted sum technique to combine them in one single scalar function. The criteria are: (1) to control the accuracy of the slowness vector estimation using the time domain beamforming method, (2) to measure the waveform coherency of the array elements, (3) to select events with lower location error and (4) to select traces with high energy of specific phases, that is, sp- or ps-phases. The proposed procedure is verified using synthetic data as well as real examples for the Vogtland region in Northwest Bohemia. We discussed the possible application of the optimized source arrays to identify the location of scatterers in the velocity model by presenting a synthetic test and an example using real waveforms.
KW  - location of scatterers
KW  - optimization
KW  - source array design
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa002
SN  - 0956-540X
SN  - 1365-246X
VL  - 221
IS  - 1
SP  - 352
EP  - 370
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Morishita, Yu
A1  - Lazecky, Milan
A1  - Wright, Tim J.
A1  - Weiss, Jonathan R.
A1  - Elliott, John R.
A1  - Hooper, Andy
T1  - LiCSBAS
BT  - an open-source InSAR time series analysis package integrated with the LiCSAR automated Sentinel-1 InSAR processor
JF  - Remote sensing
N2  - For the past five years, the 2-satellite Sentinel-1 constellation has provided abundant and useful Synthetic Aperture Radar (SAR) data, which have the potential to reveal global ground surface deformation at high spatial and temporal resolutions. However, for most users, fully exploiting the large amount of associated data is challenging, especially over wide areas. To help address this challenge, we have developed LiCSBAS, an open-source SAR interferometry (InSAR) time series analysis package that integrates with the automated Sentinel-1 InSAR processor (LiCSAR). LiCSBAS utilizes freely available LiCSAR products, and users can save processing time and disk space while obtaining the results of InSAR time series analysis. In the LiCSBAS processing scheme, interferograms with many unwrapping errors are automatically identified by loop closure and removed. Reliable time series and velocities are derived with the aid of masking using several noise indices. The easy implementation of atmospheric corrections to reduce noise is achieved with the Generic Atmospheric Correction Online Service for InSAR (GACOS). Using case studies in southern Tohoku and the Echigo Plain, Japan, we demonstrate that LiCSBAS applied to LiCSAR products can detect both large-scale (>100 km) and localized (similar to km) relative displacements with an accuracy of <1 cm/epoch and similar to 2 mm/yr. We detect displacements with different temporal characteristics, including linear, periodic, and episodic, in Niigata, Ojiya, and Sanjo City, respectively. LiCSBAS and LiCSAR products facilitate greater exploitation of globally available and abundant SAR datasets and enhance their applications for scientific research and societal benefit.
KW  - InSAR
KW  - Sentinel-1
KW  - time series analysis
KW  - deformation monitoring
KW  - tectonics
KW  - subsidence
KW  - automatic processing
KW  - global
Y1  - 2020
U6  - https://doi.org/10.3390/rs12030424
SN  - 2072-4292
VL  - 12
IS  - 3
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Zhu, Chuanbin
A1  - Cotton, Fabrice
A1  - Pilz, Marco
T1  - Detecting site resonant frequency using HVSR
BT  - Fourier versus response spectrum and the first versus the highest peak frequency
JF  - Bulletin of the Seismological Society of America : BSSA
N2  - In this investigation, we examine the uncertainties using the horizontal-to-vertical spectral ratio (HVSR) technique on earthquake recordings to detect site resonant frequencies at 207 KiK-net sites. Our results show that the scenario dependence of response (pseudospectral acceleration) spectral ratio could bias the estimates of resonant frequencies for sites having multiple significant peaks with comparable amplitudes. Thus, the Fourier amplitude spectrum (FAS) should be preferred in computing HVSR. For more than 80% of the investigated sites, the first peak (in the frequency domain) on the average HVSR curve over multiple sites coincides with the highest peak. However, for sites with multiple peaks, the highest peak frequency (f(p)) is less susceptible to the selection criteria of significant peaks and the extent of smoothing to spectrum than the first peak frequency (f(0)). Meanwhile, in comparison to the surface-to-borehole spectral ratio, f(0) tends to underestimate the predominant frequency (at which the largest amplification occurs) more than f(p). In addition, in terms of characterizing linear site response, f(p) shows a better overall performance than f(0). Based on these findings, we thus recommend that seismic network operators provide f(p) on the average HVSRFAS curve as a priority, ideally together with the average HVSRFAS curve in site characterization.
Y1  - 2020
U6  - https://doi.org/10.1785/0120190186
SN  - 0037-1106
SN  - 1943-3573
VL  - 110
IS  - 2
SP  - 427
EP  - 440
PB  - Seismological Society of America
CY  - El Cerito, Calif.
ER  - 
TY  - JOUR
A1  - Tronicke, Jens
A1  - Allroggen, Niklas
A1  - Biermann, Felix
A1  - Fanselow, Florian
A1  - Guillemoteau, Julien
A1  - Krauskopf, Christof
A1  - Lück, Erika
T1  - Rapid multiscale analysis of near-surface geophysical anomaly maps
BT  - application to an archaeogeophysical data set
JF  - Geophysics
N2  - In near- surface geophysics, ground-based mapping surveys are routinely used in a variety of applications including those from archaeology, civil engineering, hydrology, and soil science. The resulting geophysical anomaly maps of, for example, magnetic or electrical parameters are usually interpreted to laterally delineate subsurface structures such as those related to the remains of past human activities, subsurface utilities and other installations, hydrological properties, or different soil types. To ease the interpretation of such data sets, we have developed a multiscale processing, analysis, and visualization strategy. Our approach relies on a discrete redundant wavelet transform (RWT) implemented using cubic-spline filters and the a trous algorithm, which allows to efficiently compute a multiscale decomposition of 2D data using a series of 1D convolutions. The basic idea of the approach is presented using a synthetic test image, whereas our archaeogeophysical case study from northeast Germany demonstrates its potential to analyze and process rather typical geophysical anomaly maps including magnetic and topographic data. Our vertical-gradient magnetic data show amplitude variations over several orders of magnitude, complex anomaly patterns at various spatial scales, and typical noise patterns, whereas our topographic data show a distinct hill structure superimposed by a microtopographic stripe pattern and random noise. Our results demonstrate that the RWT approach is capable to successfully separate these components and that selected wavelet planes can be scaled and combined so that the reconstructed images allow for a detailed, multiscale structural interpretation also using integrated visualizations of magnetic and topographic data. Because our analysis approach is straightforward to implement without laborious parameter testing and tuning, computationally efficient, and easily adaptable to other geophysical data sets, we believe that it can help to rapidly analyze and interpret different geophysical mapping data collected to address a variety of near-surface applications from engineering practice and research.
KW  - archaeology
KW  - case history
KW  - near surface
KW  - magnetics
KW  - decomposition
Y1  - 2020
U6  - https://doi.org/10.1190/GEO2019-0564.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 85
IS  - 4
SP  - B109
EP  - B118
PB  - Society of Exploration Geophysicists
CY  - Tulsa, Okla.
ER  - 
TY  - JOUR
A1  - Wolf, Sabina
A1  - Pham, My
A1  - Matthews, Nathanial
A1  - Bubeck, Philip
T1  - Understanding the implementation gap
BT  - policy-makers’ perceptions of ecosystem-based adaptation in Central Vietnam
JF  - Climate & development
N2  - In recent years, nature-based solutions are receiving increasing attention in the field of disaster risk reduction and climate change adaptation as inclusive, no regret approaches. Ecosystem-based adaptation (EbA) can mitigate the impacts of climate change, build resilience and tackle environmental degradation thereby supporting the targets set by the 2030 Agenda, the Paris Agreement and the Sendai Framework. Despite these benefits, EbA is still rarely implemented in practice. To better understand the barriers to implementation, this research examines policy-makers' perceptions of EbA, using an extended version of Protection Motivation Theory as an analytical framework. Through semi-structured interviews with policy-makers at regional and provincial level in Central Vietnam, it was found that EbA is generally considered a promising response option, mainly due to its multiple ecosystem-service benefits. The demand for EbA measures was largely driven by the perceived consequences of natural hazards and climate change. Insufficient perceived response efficacy and time-lags in effectiveness for disaster risk reduction were identified as key impediments for implementation. Pilot projects and capacity building on EbA are important means to overcome these perceptual barriers. This paper contributes to bridging the knowledge-gap on political decision-making regarding EbA and can, thereby, promote its mainstreaming into policy plans.
KW  - climate change
KW  - ecosystem-based adaptation
KW  - risk perception
KW  - protection
KW  - motivation theory
KW  - decision making
Y1  - 2020
U6  - https://doi.org/10.1080/17565529.2020.1724068
SN  - 1756-5529
SN  - 1756-5537
VL  - 13
IS  - 1
SP  - 81
EP  - 94
PB  - Taylor & Francis LTD
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Rötzler, Jochen
A1  - Timmerman, Martin Jan
T1  - Geochronological and petrological constraints from the evolution in the Saxon Granulite Massif, Germany, on the Variscan continental collision orogeny
JF  - Journal of metamorphic geology
N2  - Controversy over the plate tectonic affinity and evolution of the Saxon granulites in a two- or multi-plate setting during inter- or intracontinental collision makes the Saxon Granulite Massif a key area for the understanding of the Palaeozoic Variscan orogeny. The massif is a large dome structure in which tectonic slivers of metapelite and metaophiolite units occur along a shear zone separating a diapir-like body of high-Pgranulite below from low-Pmetasedimentary rocks above. Each of the upper structural units records a different metamorphic evolution until its assembly with the exhuming granulite body. New age and petrologic data suggest that the metaophiolites developed from early Cambrian protoliths during high-Pamphibolite facies metamorphism in the mid- to late-Devonian and thermal overprinting by the exhuming hot granulite body in the early Carboniferous. A correlation of new Ar-Ar biotite ages with publishedP-T-tdata for the granulites implies that exhumation and cooling of the granulite body occurred at average rates of similar to 8 mm/year and similar to 80 degrees C/Ma, with a drop in exhumation rate from similar to 20 to similar to 2.5 mm/year and a slight rise in cooling rate between early and late stages of exhumation. A time lag ofc. 2 Ma between cooling through the closure temperatures for argon diffusion in hornblende and biotite indicates a cooling rate of 90 degrees C/Ma when all units had assembled into the massif. A two-plate model of the Variscan orogeny in which the above evolution is related to a short-lived intra-Gondwana subduction zone conflicts with the oceanic affinity of the metaophiolites and the timescale ofc. 50 Ma for the metamorphism. Alternative models focusing on the internal Variscan belt assume distinctly different material paths through the lower or upper crust for strikingly similar granulite massifs. An earlier proposed model of bilateral subduction below the internal Variscan belt may solve this problem.
KW  - geochronology
KW  - granulite
KW  - high-Pmetamorphism
KW  - metaophiolite
KW  - Variscan
KW  - orogeny
Y1  - 2020
U6  - https://doi.org/10.1111/jmg.12559
SN  - 0263-4929
SN  - 1525-1314
VL  - 39
IS  - 1
SP  - 3
EP  - 38
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Scharf, Andreas
A1  - Sudo, Masafumi
A1  - Pracejus, Bernhard
A1  - Mattern, Frank
A1  - Callegari, Ivan
A1  - Bauer, Wilfried
A1  - Scharf, Katharina
T1  - Late Lutetian (Eocene) mafic intrusion into shallow marine platform deposits north of the Oman Mountains (Rusayl Embayment) and its tectonic significance
JF  - Journal of African earth sciences
N2  - A silica undersaturated alkali-olivine basanitic magma intruded the late Paleocene/early Eocene Jafnayn Formation near Muscat. Geochemical analyses indicate that a significant amount of host rock (limestone) was assimilated into the magma. We dated the basanite as 42.7 +/- 1.0 Ma (2 sigma error; late Lutetian), using the whole rock Ar-40/Ar-39 step-wise heating technique. Intrusion occurred in the hanging wall of a major regional extensional shear zone (Frontal Range Fault, FRF) bounding the northern margin of two domes within the Oman Mountains (Jabal Akhdar and Saih Hatat domes). Two shear intervals along the FRF have been documented. The first interval lasted immediately after emplacement of the Semail Ophiolite (latest Cretaceous-early Eocene) while the second and poorly constrained interval was assumed to have occurred during the Oligocene. 

The proximity of the basanite to the FRF suggests that magma used extensional faults for the upper part of its ascent path. Reactivated Permian rift faults of the Pangaea rift or other preexisting faults may have been used for the lower ascent part. 

We conclude that the basanite intrusion coincided with the onset of the second deformation interval along the FRF, because (1) the position of the basanite is near a dextral releasing bend, associated with the second shear interval, (2) the overlap of our Ar-40/Ar-39 age with the cooling curves for rocks from the nearby Jabal Akhdar Dome, and (3) the basanite postdates the first FRF deformation episode by > 10 Ma. Thus, the second interval along the FRF had started already during the late Lutetian and probably lasted into the Miocene.
KW  - Ar-40/Ar-39 age
KW  - Jafnayn formation
KW  - gravitational collapse
KW  - Basanite
KW  - extension
KW  - Limestone assimilation in basanite
Y1  - 2020
U6  - https://doi.org/10.1016/j.jafrearsci.2020.103941
SN  - 1464-343X
SN  - 1879-1956
VL  - 170
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Weatherill, Graeme
A1  - Cotton, Fabrice
T1  - A ground motion logic tree for seismic hazard analysis in the stable cratonic region of Europe
BT  - regionalisation, model selection and development of a scaled backbone approach
JF  - Bulletin of earthquake engineering : official publication of the European Association for Earthquake Engineering
N2  - Regions of low seismicity present a particular challenge for probabilistic seismic hazard analysis when identifying suitable ground motion models (GMMs) and quantifying their epistemic uncertainty. The 2020 European Seismic Hazard Model adopts a scaled backbone approach to characterise this uncertainty for shallow seismicity in Europe, incorporating region-to-region source and attenuation variability based on European strong motion data. This approach, however, may not be suited to stable cratonic region of northeastern Europe (encompassing Finland, Sweden and the Baltic countries), where exploration of various global geophysical datasets reveals that its crustal properties are distinctly different from the rest of Europe, and are instead more closely represented by those of the Central and Eastern United States. Building upon the suite of models developed by the recent NGA East project, we construct a new scaled backbone ground motion model and calibrate its corresponding epistemic uncertainties. The resulting logic tree is shown to provide comparable hazard outcomes to the epistemic uncertainty modelling strategy adopted for the Eastern United States, despite the different approaches taken. Comparison with previous GMM selections for northeastern Europe, however, highlights key differences in short period accelerations resulting from new assumptions regarding the characteristics of the reference rock and its influence on site amplification.
KW  - ground motion models
KW  - stable craton
KW  - regionalisation
KW  - epistemic
KW  - uncertainty
KW  - Europe
Y1  - 2020
U6  - https://doi.org/10.1007/s10518-020-00940-x
SN  - 1570-761X
SN  - 1573-1456
VL  - 18
IS  - 14
SP  - 6119
EP  - 6148
PB  - Springer Science + Business Media B.V.
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Zhu, Chuanbin
A1  - Pilz, Marco
A1  - Cotton, Fabrice
T1  - Evaluation of a novel application of earthquake HVSR in site-specific amplification estimation
JF  - Soil dynamics and earthquake engineering
N2  - Ground response analyses (GRA) model the vertical propagations of SH waves through flat-layered media (1DSH) and are widely carried out to evaluate local site effects in practice. Horizontal-to-vertical spectral ratio (HVSR) technique is a cost-effective approach to extract certain site-specific information, e.g., site fundamental frequency (f(0)), but HVSR values cannot be directly used to approximate the levels of S-wave amplifications. Motivated by the work of Kawase et al. (2019), we propose a procedure to correct earthquake HVSR amplitudes for direct amplification estimations. The empirical correction compensates HVSR by generic vertical amplification spectra categorized by the vertical fundamental frequency (f(0v)) via kappa-means clustering. In this investigation, we evaluate the effectiveness of the corrected HVSR in approximating observed linear amplifications in comparison with 1DSH modellings. We select a total of 90 KiK-net (Kiban Kyoshin network) surface-downhole sites which are found to have no velocity contrasts below their boreholes and thus of which surface-to-borehole spectral ratios (SBSRs) can be taken as their empirical transfer functions (ETFs). 1DSH-based theoretical transfer functions (TTFs) are computed in the linear domain considering uncertainties in Vs profiles through randomizations. Five goodness-of-fit metrics are adopted to gauge the closeness between observed (ETF) and predicted (i.e., TTF and corrected HVSR) amplifications in both amplitude and spectral shape over frequencies from f(0) to 25 Hz. We find that the empirical correction to HVSR is highly effective and achieves a "good match" in both spectral shape and amplitude at the majority of the 90 KiK-net sites, as opposed to less than one-third for the 1DSH modelling. In addition, the empirical correction does not require a velocity model, which GRAs require, and thus has great potentials in seismic hazard assessments.
KW  - site amplification
KW  - HVSR
KW  - ground response analysis
KW  - KiK-net
KW  - earthquake
Y1  - 2020
U6  - https://doi.org/10.1016/j.soildyn.2020.106301
SN  - 0267-7261
SN  - 1879-341X
VL  - 139
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Riedl, Simon
A1  - Melnick, Daniel
A1  - Mibei, Geoffrey K.
A1  - Njue, Lucy
A1  - Strecker, Manfred
T1  - Continental rifting at magmatic centres
BT  - structural implications from the Late Quaternary Menengai Caldera, central Kenya Rift
JF  - Journal of the geological society
N2  - The structural evolution of calderas in rifts helps to characterize the spatiotemporal relationships between magmatism, long wavelength crustal deformation and the formation of tectonic deformation zones along the rift axis. We document the structural characteristics of the c. 36 ka old Menengai Caldera located within a young zone of extension in the central Kenya Rift. Field mapping and high-resolution digital surface models show that NNE-striking Holocene normal faults perpendicular to the regional ESE-WNWextension direction dominate the interior sectors of the rift. Inside the caldera, these structures are overprinted by post-collapse doming and faulting of the magmatic centre, resulting in obliquely slipping normal faults bounding a resurgence horst. Radiocarbon dating of faulted units as young as 5 ka cal BP and the palaeo-shorelines of a lake formed during the African Humid Period in the Nakuru Basin indicate that volcanism and fault activity inside and in the vicinity of Menengai must have been sustained during the Holocene. Our analysis confirms that the caldera is located at the centre of an extending rift segment and suggests that other magmatic centres and young zones of faulting along the volcano-tectonic axis of the Kenya Rift may constitute nucleation points of faulting that ultimately foster future continental break-up.
Y1  - 2020
U6  - https://doi.org/10.1144/jgs2019-021
SN  - 0016-7649
SN  - 2041-479X
VL  - 177
IS  - 1
SP  - 153
EP  - 169
PB  - Geological Soc. Publ. House
CY  - Bath
ER  - 
TY  - JOUR
A1  - Schmidt, Lennart
A1  - Hesse, Falk
A1  - Attinger, Sabine
A1  - Kumar, Rohini
T1  - Challenges in applying machine learning models for hydrological inference
BT  - a case study for flooding events across Germany
JF  - Water resources research
N2  - Machine learning (ML) algorithms are being increasingly used in Earth and Environmental modeling studies owing to the ever-increasing availability of diverse data sets and computational resources as well as advancement in ML algorithms. Despite advances in their predictive accuracy, the usefulness of ML algorithms for inference remains elusive. In this study, we employ two popular ML algorithms, artificial neural networks and random forest, to analyze a large data set of flood events across Germany with the goals to analyze their predictive accuracy and their usability to provide insights to hydrologic system functioning. The results of the ML algorithms are contrasted against a parametric approach based on multiple linear regression. For analysis, we employ a model-agnostic framework named Permuted Feature Importance to derive the influence of models' predictors. This allows us to compare the results of different algorithms for the first time in the context of hydrology. Our main findings are that (1) the ML models achieve higher prediction accuracy than linear regression, (2) the results reflect basic hydrological principles, but (3) further inference is hindered by the heterogeneity of results across algorithms. Thus, we conclude that the problem of equifinality as known from classical hydrological modeling also exists for ML and severely hampers its potential for inference. To account for the observed problems, we propose that when employing ML for inference, this should be made by using multiple algorithms and multiple methods, of which the latter should be embedded in a cross-validation routine.
KW  - machine learning
KW  - inference
KW  - floods
Y1  - 2020
U6  - https://doi.org/10.1029/2019WR025924
SN  - 0043-1397
SN  - 1944-7973
VL  - 56
IS  - 5
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Otto, Christopher
A1  - Kempka, Thomas
T1  - Synthesis gas composition prediction for underground coal gasification using a thermochemical equilibrium modeling approach
JF  - Energies
N2  - Underground coal gasification (UCG) is an in situ conversion technique that enables the production of high-calorific synthesis gas from resources that are economically not minable by conventional methods. A broad range of end-use options is available for the synthesis gas, including fuels and chemical feedstock production. Furthermore, UCG also offers a high potential for integration with Carbon Capture and Storage (CCS) to mitigate greenhouse gas emissions. In the present study, a stoichiometric equilibrium model, based on minimization of the Gibbs function has been used to estimate the equilibrium composition of the synthesis gas. Thereto, we further developed and applied a proven thermodynamic equilibrium model to simulate the relevant thermochemical coal conversion processes (pyrolysis and gasification). Our modeling approach has been validated against thermodynamic models, laboratory gasification experiments and UCG field trial data reported in the literature. The synthesis gas compositions have been found to be in good agreement under a wide range of different operating conditions. Consequently, the presented modeling approach enables an efficient quantification of synthesis gas quality resulting from UCG, considering varying coal and oxidizer compositions at deposit-specific pressures and temperatures.
KW  - underground coal gasification
KW  - Cantera
KW  - thermodynamic equilibrium
KW  - composition
KW  - synthesis gas
KW  - oxidizer
Y1  - 2020
U6  - https://doi.org/10.3390/en13051171
SN  - 1996-1073
VL  - 13
IS  - 5
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - Beiter, Daniel
A1  - Tronicke, Jens
T1  - Ground-penetrating radar monitoring of fast subsurface processes
JF  - Geophysics
N2  - Earth and environmental sciences rely on detailed information about subsurface processes. Whereas geophysical techniques typically provide highly resolved spatial images, monitoring subsurface processes is often associated with enormous effort and, therefore, is usually limited to point information in time or space. Thus, the development of spatial and temporal continuous field monitoring methods is a major challenge for the understanding of subsurface processes. We have developed a novel method for ground-penetrating-radar (GPR) reflection monitoring of subsurface flow processes under unsaturated conditions and applied it to a hydrological infiltration experiment performed across a periglacial slope deposit in northwest Luxembourg. Our approach relies on a spatial and temporal quasicontinuous data recording and processing, followed by an attribute analysis based on analyzing differences between individual time steps. The results demonstrate the ability of time-lapse GPR monitoring to visualize the spatial and temporal dynamics of preferential flow processes with a spatial resolution in the order of a few decimeters and temporal resolution in the order of a few minutes. We observe excellent agreement with water table information originating from different boreholes. This demonstrates the potential of surface-based GPR reflection monitoring to observe the spatiotemporal dynamics of water movements in the subsurface. It provides valuable, and so far not accessible, information for example in the field of hydrology and pedology that allows studying the actual subsurface processes rather than deducing them from point information.
Y1  - 2020
U6  - https://doi.org/10.1190/GEO2019-0737.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 85
IS  - 3
SP  - A19
EP  - A23
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Richter, Gudrun
A1  - Hainzl, Sebastian
A1  - Dahm, Torsten
A1  - Zöller, Gert
T1  - Stress-based, statistical modeling of the induced seismicity at the Groningen gas field
BT  - the Netherlands
JF  - Environmental earth sciences
N2  - Groningen is the largest onshore gas field under production in Europe. The pressure depletion of the gas field started in 1963. In 1991, the first induced micro-earthquakes have been located at reservoir level with increasing rates in the following decades. Most of these events are of magnitude less than 2.0 and cannot be felt. However, maximum observed magnitudes continuously increased over the years until the largest, significant event with ML=3.6 was recorded in 2014, which finally led to the decision to reduce the production. This causal sequence displays the crucial role of understanding and modeling the relation between production and induced seismicity for economic planing and hazard assessment. Here we test whether the induced seismicity related to gas exploration can be modeled by the statistical response of fault networks with rate-and-state-dependent frictional behavior. We use the long and complete local seismic catalog and additionally detailed information on production-induced changes at the reservoir level to test different seismicity models. Both the changes of the fluid pressure and of the reservoir compaction are tested as input to approximate the Coulomb stress changes. We find that the rate-and-state model with a constant tectonic background seismicity rate can reproduce the observed long delay of the seismicity onset. In contrast, so-called Coulomb failure models with instantaneous earthquake nucleation need to assume that all faults are initially far from a critical state of stress to explain the delay. Our rate-and-state model based on the fluid pore pressure fits the spatiotemporal pattern of the seismicity best, where the fit further improves by taking the fault density and orientation into account. Despite its simplicity with only three free parameters, the rate-and-state model can reproduce the main statistical features of the observed activity.
KW  - induced seismicity
KW  - modeling
KW  - statistical seismology
KW  - forecast
Y1  - 2020
U6  - https://doi.org/10.1007/s12665-020-08941-4
SN  - 1866-6280
SN  - 1866-6299
VL  - 79
IS  - 11
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Rein, Theresa
A1  - Hannemann, Katrin
A1  - Thomas, Christine
A1  - Korn, Michael
T1  - Location and characteristics of the X-discontinuity beneath SW Morocco and the adjacent shelf area using P-wave receiver functions
JF  - Geophysical journal international
N2  - Receiver function approaches have proven to be valuable for the investigation of crustal and upper mantle discontinuities whose sharp changes in seismic velocities cause wave conversions. While the crustal and mantle transition zone discontinuities are largely understood, the X-discontinuity at 250-350 km depth is still an object of controversial debate. The origin and global distribution of this structure with a velocity jump of 1.5-4.8% for compressional and shear waves is still unexplained. Although the crustal and mantle transition zone discontinuities beneath SW Morocco and surroundings have been investigated, only a few studies observed the X-discontinuity and place the depth at 260-370 km beneath the region of western Morocco. In order to better locate and characterize the X-discontinuity beneath southwest Morocco, we create P-wave receiver functions using data recorded by the Morocco-Munster array and detect the X-discontinuity at apparent depths of 285-350 km. In the western part of our study region we find apparent depths of similar to 310-340 km. The eastern part of the study area appears more complex: we locate two velocity jumps at apparent depths of around 285-295 km and 330-350 km in the northeast, and in the southeast we find a discontinuity at apparent depths of 340-350 km. Due to the large depth range and the twofold appearance of the X-discontinuity, we suggest that two different phase transitions cause the X-discontinuity beneath SW Morocco. The velocity contrasts at larger depths likely point to the coesite-stishovite phase transition occurring in deep eclogitic pools. The shallower depths can be explained by the transition from orthoenstatite to high-pressure clinoenstatite which requires the reaction between eclogite and peridotite to form orthopyroxene-rich peridotite. This reaction is likely related to previously proposed small-scale mantle upwellings beneath SW Morocco. Since both phase transitions require eclogite occurrence, the location of the X-discontinuity in this region can be used to indicate the location of recycled oceanic crust.
KW  - body waves
KW  - mantle discontinuities
KW  - NW Morocco
KW  - P-waves
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa379
SN  - 0956-540X
SN  - 1365-246X
VL  - 223
IS  - 3
SP  - 1780
EP  - 1793
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Saki, Adel
A1  - Miri, Mirmohammad
A1  - Oberhänsli, Roland
T1  - High temperature - low pressure metamorphism during subduction of Neo-Tethys beneath the Iranian plate
BT  - evidence for mafic migmatite formation in the Alvand complex (western Iran)
JF  - Mineralogy and petrology
N2  - Subduction of Neo-Tethys oceanic lithosphere beneath the Iranian plate during the Mesozoic formed several igneous bodies of ultramafic to intermediate and felsic composition. Intrusion of these magmas into a regional metamorphic sequence (the Sanandaj-Sirjan Zone) caused partial melting and formation of migmatites with meta-pelitic protoliths. The Alvand complex (west Iran) is a unique area comprising migmatites of both mafic and pelitic protoliths. In this area, the gabbroic rocks contain veins of leucosome at their contact with pyroxenite and olivine gabbro. These leucosomes are geochemically and mineralogically different from leucosomes of the meta-pelitic migmatites and clearly show properties of I-type granites. Microscopic observations and whole rock compositions of the mafic migmatite leucosomes show that migmatization occurred through partial melting of biotite, hornblende and plagioclase. Thermobarometric calculations indicate 800 degrees C and 3.7 kbar for partial melting, although phase diagram modeling demonstrates that the presence of water could decrease the solidus temperature by about 40 degrees C. Our results suggest an asthenospheric magma upwelling as the source of heat for partial melting of the gabbroic rock during subduction of Neo-Tethys oceanic crust under the western edge of the Iranian plate. The present study also reveals relationships between migmatization and formation of S- and I -type granites in the area.
KW  - partial melting
KW  - mafic migmatite
KW  - pelitic migmatite
KW  - Neo-Tethys
KW  - subduction
KW  - Gabbroic rocks
Y1  - 2020
U6  - https://doi.org/10.1007/s00710-020-00721-z
SN  - 0930-0708
SN  - 1438-1168
VL  - 114
IS  - 6
SP  - 539
EP  - 557
PB  - Springer
CY  - Wien [u.a.]
ER  - 
TY  - JOUR
A1  - Weiss, Jonathan R.
A1  - Walters, Richard J.
A1  - Morishita, Yu
A1  - Wright, Tim J.
A1  - Lazecky, Milan
A1  - Wang, Hua
A1  - Hussain, Ekbal
A1  - Hooper, Andrew J.
A1  - Elliott, John R.
A1  - Rollins, Chris
A1  - Yu, Chen
A1  - Gonzalez, Pablo J.
A1  - Spaans, Karsten
A1  - Li, Zhenhong
A1  - Parsons, Barry
T1  - High-resolution surface velocities and strain for Anatolia from Sentinel-1 InSAR and GNSS data
JF  - Geophysical research letters
N2  - Measurements of present-day surface deformation are essential for the assessment of long-term seismic hazard. The European Space Agency's Sentinel-1 satellites enable global, high-resolution observation of crustal motion from Interferometric Synthetic Aperture Radar (InSAR). We have developed automated InSAR processing systems that exploit the first similar to 5 years of Sentinel-1 data to measure surface motions for the similar to 800,000-km(2) Anatolian region. Our new 3-D velocity and strain rate fields illuminate deformation patterns dominated by westward motion of Anatolia relative to Eurasia, localized strain accumulation along the North and East Anatolian Faults, and rapid vertical signals associated with anthropogenic activities and to a lesser extent extension across the grabens of western Anatolia. We show that automatically processed Sentinel-1 InSAR data can characterize details of the velocity and strain rate fields with high resolution and accuracy over large regions. These results are important for assessing the relationship between strain accumulation and release in earthquakes. <br /> Plain Language Summary Satellite-based measurements of small rates of motion of the Earth's surface made at high spatial resolutions and over large areas are important for many geophysical applications including improving earthquake hazard models. We take advantage of recent advances in geodetic techniques in order to measure surface velocities and tectonic strain accumulation across the Anatolia region, including the highly seismogenic and often deadly North Anatolian Fault. We show that by combining Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) data with Global Navigation Satellite System (GNSS) measurements we can enhance our view of surface deformation associated with active tectonics, the earthquake cycle, and anthropogenic processes.
Y1  - 2020
U6  - https://doi.org/10.1029/2020GL087376
SN  - 0094-8276
SN  - 1944-8007
VL  - 47
IS  - 17
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Baroni, Gabriele
A1  - Francke, Till
T1  - An effective strategy for combining variance- and distribution-based global sensitivity analysis
JF  - Environmental modelling & software with environment data news
N2  - We present a new strategy for performing global sensitivity analysis capable to estimate main and interaction effects from a generic sampling design. The new strategy is based on a meaningful combination of varianceand distribution-based approaches. The strategy is tested on four analytic functions and on a hydrological model. Results show that the analysis is consistent with the state-of-the-art Saltelli/Jansen formula but to better quantify the interaction effect between the input factors when the output distribution is skewed. Moreover, the estimation of the sensitivity indices is much more robust requiring a smaller number of simulations runs. Specific settings and alternative methods that can be integrated in the new strategy are also discussed. Overall, the strategy is considered as a new simple and effective tool for performing global sensitivity analysis that can be easily integrated in any environmental modelling framework.
KW  - global sensitivity analysis
KW  - variance
KW  - distribution
KW  - generic sampling
KW  - design
Y1  - 2020
U6  - https://doi.org/10.1016/j.envsoft.2020.104851
SN  - 1364-8152
SN  - 1873-6726
VL  - 134
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Ziemann, Martin Andreas
A1  - Madariaga, Juan Manuel
T1  - Applications of Raman spectroscopy in art and archaeology
JF  - Journal of Raman spectroscopy
N2  - The 10th edition of the International Congress on the Application of Raman Spectroscopy in Art and Archaeology (RAA2019) was held in Potsdam (Germany) from 3 to 7 September 2019, with eight keynote lectures, 35 oral presentations and 18 Poster Presentations. The number of active participants was 68 delegates from 20 countries among the 236 authors that presented at least one work.
Y1  - 2020
U6  - https://doi.org/10.1002/jrs.6054
SN  - 0377-0486
SN  - 1097-4555
VL  - 52
IS  - 1
SP  - 8
EP  - 14
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Morgenstern, Anne
A1  - Overduin, Pier Paul
A1  - Günther, Frank
A1  - Stettner, Samuel
A1  - Ramage, Justine
A1  - Schirrmeister, Lutz
A1  - Grigoriev, Mikhail N.
A1  - Grosse, Guido
T1  - Thermo-erosional valleys in Siberian ice-rich permafrost
JF  - Permafrost and Periglacial Processes
N2  - Thermal erosion is a major mechanism of permafrost degradation, resulting in characteristic landforms. We inventory thermo-erosional valleys in ice-rich coastal lowlands adjacent to the Siberian Laptev Sea based on remote sensing, Geographic Information System (GIS), and field investigations for a first regional assessment of their spatial distribution and characteristics. Three study areas with similar geological (Yedoma Ice Complex) but diverse geomorphological conditions vary in valley areal extent, incision depth, and branching geometry. The most extensive valley networks are incised deeply (up to 35 m) into the broad inclined lowland around Mamontov Klyk. The flat, low-lying plain forming the Buor Khaya Peninsula is more degraded by thermokarst and characterized by long valleys of lower depth with short tributaries. Small, isolated Yedoma Ice Complex remnants in the Lena River Delta predominantly exhibit shorter but deep valleys. Based on these hydrographical network and topography assessments, we discuss geomorphological and hydrological connections to erosion processes. Relative catchment size along with regional slope interact with other Holocene relief-forming processes such as thermokarst and neotectonics. Our findings suggest that thermo-erosional valleys are prominent, hitherto overlooked permafrost degradation landforms that add to impacts on biogeochemical cycling, sediment transport, and hydrology in the degrading Siberian Yedoma Ice Complex.
KW  - geomorphology
KW  - periglacial landscapes
KW  - permafrost degradation
KW  - thermal
KW  - erosion
KW  - valley distribution
KW  - Yedoma Ice Complex
Y1  - 2020
U6  - https://doi.org/10.1002/ppp.2087
SN  - 1045-6740
SN  - 1099-1530
VL  - 32
IS  - 1
SP  - 59
EP  - 75
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Oberhänsli, Roland
T1  - Deep-time Digital Earth (DDE) the first IUGS big science program
JF  - Journal of the Geological Society of India
Y1  - 2020
U6  - https://doi.org/10.1007/s12594-020-1420-5
SN  - 0016-7622
SN  - 0974-6889
VL  - 95
IS  - 3
SP  - 223
EP  - 226
PB  - Springer India
CY  - New Delhi
ER  - 
TY  - JOUR
A1  - Steinberg, Andreas
A1  - Sudhaus, Henriette
A1  - Heimann, Sebastian
A1  - Krüger, Frank
T1  - Sensitivity of InSAR and teleseismic observations to earthquake rupture segmentation
JF  - Geophysical journal international
N2  - Earthquakes often rupture across more than one fault segment. If such rupture segmentation occurs on a significant scale, a simple point-source or one-fault model may not represent the rupture process well. As a consequence earthquake characteristics inferred, based on one-source assumptions, may become systematically wrong. This might have effects on follow-up analyses, for example regional stress field inversions and seismic hazard assessments. While rupture segmentation is evident for most M-w > 7 earthquakes, also smaller ones with 5.5 < M-w < 7 can be segmented. We investigate the sensitivity of globally available data sets to rupture segmentation and their resolution to reliably estimate the mechanisms in presence of segmentation. We focus on the sensitivity of InSAR (Interferometric Synthetic Aperture Radar) data in the static near-field and seismic waveforms in the far-field of the rupture and carry out non-linear and Bayesian optimizations of single-source and two-sources kinematic models (double-couple point sources and finite, rectangular sources) using InSAR and teleseismic waveforms separately. Our case studies comprises of four M-w 6-7 earthquakes: the 2009 L'Aquila and 2016 Amatrice (Italy) and the 2005 and 2008 Zhongba (Tibet) earthquakes. We contrast the data misfits of different source complexity by using the Akaike informational criterion (AIC). We find that the AIC method is well suited for data-driven inferences on significant rupture segmentation for the given data sets. This is based on our observation that an AIC-stated significant improvement of data fit for two-segment models over one-segment models correlates with significantly different mechanisms of the two source segments and their average compared to the single-segment mechanism. We attribute these modelled differences to a sufficient sensitivity of the data to resolve rupture segmentation. Our results show that near-field data are generally more sensitive to rupture segmentation of shallow earthquakes than far-field data but that also teleseismic data can resolve rupture segmentation in the studied magnitude range. We further conclude that a significant difference in the modelled source mechanisms for different segmentations shows that an appropriate choice of model segmentation matters for a robust estimation of source mechanisms. It reduces systematic biases and trade-off and thereby improves the knowledge on the rupture. Our study presents a strategy and method to detect significant rupture segmentation such that an appropriate model complexity can be used in the source mechanism inference. A similar, systematic investigation of earthquakes in the range of M-w 5.5-7 could provide important hazard-relevant statistics on rupture segmentation. In these cases single-source models introduce a systematic bias. Consideration of rupture segmentation therefore matters for a robust estimation of source mechanisms of the studied earthquakes.
KW  - radar interferometry
KW  - waveform inversion
KW  - earthquake source observations
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa351
SN  - 0956-540X
SN  - 1365-246X
VL  - 223
IS  - 2
SP  - 875
EP  - 907
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Pilz, Marco
A1  - Cotton, Fabrice
A1  - Razafindrakoto, Hoby Njara Tendrisoa
A1  - Weatherill, Graeme
A1  - Spies, Thomas
T1  - Regional broad-band ground-shaking modelling over extended and thick sedimentary basins
BT  - An example from the Lower Rhine Embayment (Germany)
JF  - Bulletin of earthquake engineering : official publication of the European Association for Earthquake Engineering
N2  - The simulation of broad-band (0.1 to 10 + Hz) ground-shaking over deep and spatially extended sedimentary basins at regional scales is challenging. We evaluate the ground-shaking of a potential M 6.5 earthquake in the southern Lower Rhine Embayment, one of the most important areas of earthquake recurrence north of the Alps, close to the city of Cologne in Germany. In a first step, information from geological investigations, seismic experiments and boreholes is combined for deriving a harmonized 3D velocity and attenuation model of the sedimentary layers. Three alternative approaches are then applied and compared to evaluate the impact of the sedimentary cover on ground-motion amplification. The first approach builds on existing response spectra ground-motion models whose amplification factors empirically take into account the influence of the sedimentary layers through a standard parameterization. In the second approach, site-specific 1D amplification functions are computed from the 3D basin model. Using a random vibration theory approach, we adjust the empirical response spectra predicted for soft rock conditions by local site amplification factors: amplifications and associated ground-motions are predicted both in the Fourier and in the response spectra domain. In the third approach, hybrid physics-based ground-motion simulations are used to predict time histories for soft rock conditions which are subsequently modified using the 1D site-specific amplification functions computed in method 2. For large distances and at short periods, the differences between the three approaches become less notable due to the significant attenuation of the sedimentary layers. At intermediate and long periods, generic empirical ground-motion models provide lower levels of amplification from sedimentary soils compared to methods taking into account site-specific 1D amplification functions. In the near-source region, hybrid physics-based ground-motions models illustrate the potentially large variability of ground-motion due to finite source effects.
KW  - ground-motion modelling
KW  - site effects
KW  - scenario
KW  - random vibration
KW  - theory
KW  - hybrid modelling
Y1  - 2020
U6  - https://doi.org/10.1007/s10518-020-01004-w
SN  - 1570-761X
SN  - 1573-1456
VL  - 19
IS  - 2
SP  - 581
EP  - 603
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Balischewski, Christian
A1  - Behrens, Karsten
A1  - Zehbe, Kerstin
A1  - Günter, Christina
A1  - Mies, Stefan
A1  - Sperlich, Eric
A1  - Kelling, Alexandra
A1  - Taubert, Andreas
T1  - Ionic liquids with more than one metal
BT  - optical and rlectrochemical properties versus d-block metal vombinations
JF  - Chemistry - a European journal
N2  - Thirteen N-butylpyridinium salts, including three monometallic [C4Py](2)[MCl4], nine bimetallic [C4Py](2)[(M1-xMxCl4)-M-a-Cl-b] and one trimetallic compound [C4Py](2)[(M1-y-zMyMz (c) Cl4)-M-a-M-b] (M=Co, Cu, Mn; x=0.25, 0.50 or 0.75 and y=z=0.33), were synthesized and their structure and thermal and electrochemical properties were studied. All compounds are ionic liquids (ILs) with melting points between 69 and 93 degrees C. X-ray diffraction proves that all ILs are isostructural. The conductivity at room temperature is between 10(-4) and 10(-8) S cm(-1). Some Cu-based ILs reach conductivities of 10(-2) S cm(-1), which is, however, probably due to IL dec. This correlates with the optical bandgap measurements indicating the formation of large bandgap semiconductors. At elevated temperatures approaching the melting points, the conductivities reach up to 1.47x10(-1) S cm(-1) at 70 degrees C. The electrochemical stability windows of the ILs are between 2.5 and 3.0 V.
KW  - bandgap
KW  - electrochemistry
KW  - ionic liquids
KW  - metal-containing ionic
KW  - liquids
KW  - tetrahalido metallates
Y1  - 2020
U6  - https://doi.org/10.1002/chem.202003097
SN  - 0947-6539
SN  - 1521-3765
VL  - 26
IS  - 72
SP  - 17504
EP  - 17513
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Klose, Tim
A1  - Chaparro, M. Carme
A1  - Schilling, Frank
A1  - Butscher, Christoph
A1  - Klumbach, Steffen
A1  - Blum, Philipp
T1  - Fluid flow simulations of a large-scale borehole leakage experiment
JF  - Transport in Porous Media
N2  - Borehole leakage is a common and complex issue. Understanding the fluid flow characteristics of a cemented area inside a borehole is crucial to monitor and quantify the wellbore integrity as well as to find solutions to minimise existing leakages. In order to improve our understanding of the flow behaviour of cemented boreholes, we investigated experimental data of a large-scale borehole leakage tests by means of numerical modelling using three different conceptual models. The experiment was performed with an autoclave system consisting of two vessels bridged by a cement-filled casing. After a partial bleed-off at the well-head, a sustained casing pressure was observed due to fluid flow through the cementsteel composite. The aim of our simulations is to investigate and quantify the permeability of the cement-steel composite. From our model results, we conclude that the flow occurred along a preferential flow path at the cement-steel interface. Thus, the inner part of the cement core was impermeable during the duration of the experiment. The preferential flow path can be described as a highly permeable and highly porous area with an aperture of about 5 mu m and a permeability of 3 . 10(-12) m(2) (3 Darcy). It follows that the fluid flow characteristics of a cemented area inside a borehole cannot be described using one permeability value for the entire cement-steel composite. Furthermore, it can be concluded that the quality of the cement and the filling process regarding the cement-steel interface is crucial to minimize possible well leakages.
KW  - borehole leakage
KW  - sustained casing pressure
KW  - permeability test
KW  - cement
KW  - modelling
Y1  - 2020
U6  - https://doi.org/10.1007/s11242-020-01504-y
SN  - 0169-3913
SN  - 1573-1634
VL  - 136
IS  - 1
SP  - 125
EP  - 145
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Samprogna Mohor, Guilherme
A1  - Hudson, Paul
A1  - Thieken, Annegret
T1  - A comparison of factors driving flood losses in households affected by different flood types
JF  - Water resources research
N2  - Flood loss data collection and modeling are not standardized, and previous work has indicated that losses from different flood types (e.g., riverine and groundwater) may follow different driving forces. However, different flood types may occur within a single flood event, which is known as a compound flood event. Therefore, we aimed to identify statistical similarities between loss-driving factors across flood types and test whether the corresponding losses should be modeled separately. In this study, we used empirical data from 4,418 respondents from four survey campaigns studying households in Germany that experienced flooding. These surveys sought to investigate several features of the impact process (hazard, socioeconomic, preparedness, and building characteristics, as well as flood type). While the level of most of these features differed across flood type subsamples (e.g., degree of preparedness), they did so in a nonregular pattern. A variable selection process indicates that besides hazard and building characteristics, information on property-level preparedness was also selected as a relevant predictor of the loss ratio. These variables represent information, which is rarely adopted in loss modeling. Models shall be refined with further data collection and other statistical methods. To save costs, data collection efforts should be steered toward the most relevant predictors to enhance data availability and increase the statistical power of results. Understanding that losses from different flood types are driven by different factors is a crucial step toward targeted data collection and model development and will finally clarify conditions that allow us to transfer loss models in space and time. <br /> Key Points <br /> Survey data of flood-affected households show different concurrent flood types, undermining the use of a single-flood-type loss model Thirteen variables addressing flood hazard, the building, and property level preparedness are significant predictors of the building loss ratio Flood type-specific models show varying significance across the predictor variables, indicating a hindrance to model transferability
KW  - Loss modeling
KW  - Riverine floods
KW  - Surface floods
KW  - Groundwater
KW  - Levee
KW  - breaches
KW  - Compound flood event
Y1  - 2020
U6  - https://doi.org/10.1029/2019WR025943
SN  - 0043-1397
SN  - 1944-7973
VL  - 56
IS  - 4
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - León, Ena Mercedes Matienzo
T1  - Observaciones sobre el clima de Lima y sus influencias en los seres   organizados, en especial el hombre
JF  - Iberoamericana
N2  - Una extraordinaria edición actualizada de Observaciones sobre el clima de Lima y sus influencias en los seres organizados, en especial el hombre de José Hipólito Unanue y Pavón ha sido publicado en el 2018  y merece ser anunciado a la comunidad académica peruana e internacional. Este libro incluye un exhaustivo estudio in troductorio del destacado historiador Lizardo Seiner Lizárraga. Esta introducción está conformada de tres partes encabezadas por los siguientes títulos: a) Unanue: una historiografía de amplio espectro b) Textos, registros y referencias: una indagación en la biblioteca de Unanue y c) Observaciones sobre el clima de Lima: una obra en dos tiempos.
Y1  - 2020
U6  - https://doi.org/10.18441/ibam.20.2020.74.279-394
SN  - 1577-3388
SN  - 2255-520X
VL  - 20
IS  - 74
SP  - 305
EP  - 308
PB  - Vervuert
CY  - Frankfurt, Main
ER  - 
TY  - JOUR
A1  - Wang, Lei
A1  - Kwiatek, Grzegorz
A1  - Rybacki, Erik
A1  - Bohnhoff, Marco
A1  - Dresen, Georg
T1  - Injection-induced seismic moment release and laboratory fault slip
BT  - implications for fluid-induced seismicity
JF  - Geophysical research letters
N2  - Understanding the relation between injection-induced seismic moment release and operational parameters is crucial for early identification of possible seismic hazards associated with fluid-injection projects. We conducted laboratory fluid-injection experiments on permeable sandstone samples containing a critically stressed fault at different fluid pressurization rates. The observed fluid-induced fault deformation is dominantly aseismic. Fluid-induced stick-slip and fault creep reveal that total seismic moment release of acoustic emission (AE) events is related to total injected volume, independent of respective fault slip behavior. Seismic moment release rate of AE scales with measured fault slip velocity. For injection-induced fault slip in a homogeneous pressurized region, released moment shows a linear scaling with injected volume for stable slip (steady slip and fault creep), while we find a cubic relation for dynamic slip. Our results highlight that monitoring evolution of seismic moment release with injected volume in some cases may assist in discriminating between stable slip and unstable runaway ruptures.
KW  - induced seismicity
KW  - seismic moment release
KW  - fluid injection
KW  - stick slip
KW  - fault creep
KW  - acoustic emission
Y1  - 2020
U6  - https://doi.org/10.1029/2020GL089576
SN  - 0094-8276
SN  - 1944-8007
VL  - 47
IS  - 22
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Mtilatila, Lucy Mphatso Ng'ombe
A1  - Bronstert, Axel
A1  - Bürger, Gerd
A1  - Vormoor, Klaus Josef
T1  - Meteorological and hydrological drought assessment in Lake Malawi and Shire River basins (1970-2013)
JF  - Hydrological sciences journal = Journal des sciences hydrologiques
N2  - The study assesses the variability and trends of both meteorological and hydrological droughts from 1970 to 2013 in Lake Malawi and Shire River basins using the standardized precipitation index (SPI) and standardized precipitation and evaporation index (SPEI) for meteorological droughts and the lake level change index (LLCI) for hydrological droughts. Trends and slopes in droughts and drought drivers are estimated using Mann-Kendall test and Sen's slope, respectively. Results suggest that meteorological droughts are increasing due to a decrease in precipitation which is exacerbated by an increase in temperature (potential evapotranspiration). The hydrological system of Lake Malawi seems to have a >24-month memory towards meteorological conditions, since the 36-month SPEI can predict hydrological droughts 10 months in advance. The study has found the critical lake level that would trigger hydrological drought to be 474.1 m a.s.l. The increase in drought is a concern as this will have serious impacts on water resources and hydropower supply in Malawi.
KW  - Lake Malawi basin
KW  - Shire River basin
KW  - meteorological drought
KW  - hydrological drought
KW  - SPEI
KW  - SPI
KW  - trend analysis
Y1  - 2020
U6  - https://doi.org/10.1080/02626667.2020.1837384
SN  - 0262-6667
SN  - 2150-3435
VL  - 65
IS  - 16
SP  - 2750
EP  - 2764
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Streck, Charlotte
T1  - Filling in for Governments?
BT  - the role of the private actors in the International Climate Regime
JF  - Journal for European Environmental & Planning Law
N2  - The 2015 Paris Agreement on climate change abandons the Kyoto Protocol's paradigm of binding emissions targets and relies instead on countries' voluntary contributions. However, the Paris Agreement encourages not only governments but also sub-national governments, corporations and civil society to contribute to reaching ambitious climate goals. In a transition from the regulated architecture of the Kyoto Protocol to the open system of the Paris Agreement, the Agreement seeks to integrate non-state actors into the treaty-based climate regime. In 2014 the secretariat of the United Nations Framework Convention on Climate Change Peru and France created the Non-State Actor Zone for Climate Action (and launched the Global Climate Action portal). In December 2019, this portal recorded more than twenty thousand climate-commitments of private and public non-state entities, making the non-state venues of international climate meetings decisively more exciting than the formal negotiation space. This level engagement and governments' response to it raises a flurry of questions in relation to the evolving nature of the climate regime and climate change governance, including the role of private actors as standard setters and the lack of accountability mechanisms for non-state actions. This paper takes these developments as occasion to discuss the changing role of private actors in the climate regime.
KW  - climate action
KW  - Paris Agreement
KW  - non-state actors
KW  - soft law
KW  - accountability
KW  - private governance
Y1  - 2020
U6  - https://doi.org/10.1163/18760104-01701003
SN  - 1613-7272
SN  - 1876-0104
VL  - 17
IS  - 1
SP  - 5
EP  - 28
PB  - Martinus Nijhoff Pub
CY  - Leiden
ER  - 
TY  - JOUR
A1  - Koyan, Philipp
A1  - Tronicke, Jens
T1  - 3D modeling of ground-penetrating radar data across a realistic sedimentary model
JF  - Computers & geosciences : an international journal devoted to the publication of papers on all aspects of geocomputation and to the distribution of computer programs and test data sets ; an official journal of the International Association for Mathematical Geology
N2  - Ground-penetrating radar (GPR) is an established geophysical tool to explore a wide range of near-surface environments. Today, the use of synthetic GPR data is largely limited to 2D because 3D modeling is computationally more expensive. In fact, only recent developments of modeling tools and powerful hardware allow for a time-efficient computation of extensive 3D data sets. Thus, 3D subsurface models and resulting GPR data sets, which are of great interest to develop and evaluate novel approaches in data analysis and interpretation, have not been made publicly available up to now. <br /> We use a published hydrofacies data set of an aquifer-analog study within fluvio-glacial deposits to infer a realistic 3D porosity model showing heterogeneities at multiple spatial scales. Assuming fresh-water saturated sediments, we generate synthetic 3D GPR data across this model using novel GPU-acceleration included in the open-source software gprMax. We present a numerical approach to examine 3D wave-propagation effects in modeled GPR data. Using the results of this examination study, we conduct a spatial model decomposition to enable a computationally efficient 3D simulation of a typical GPR reflection data set across the entire model surface. We process the resulting GPR data set using a standard 3D structural imaging sequence and compare the results to selected input data to demonstrate the feasibility and potential of the presented modeling studies. We conclude on conceivable applications of our 3D GPR reflection data set and the underlying porosity model, which are both publicly available and, thus, can support future methodological developments in GPR and other near-surface geophysical techniques.
KW  - Applied geophysics
KW  - Ground-penetrating radar
KW  - 3D modeling
Y1  - 2020
U6  - https://doi.org/10.1016/j.cageo.2020.104422
SN  - 0098-3004
SN  - 1873-7803
VL  - 137
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Hudson, Paul
T1  - The affordability of flood risk property-level adaptation measures
JF  - Risk Analysis
N2  - The affordability of property-level adaptation measures against flooding is crucial due to the movement toward integrated flood risk management, which requires the individuals threatened by flooding to actively manage flooding. It is surprising to find that affordability is not often discussed, given the important roles that affordability and social justice play regarding flood risk management. This article provides a starting point for investigating the potential rate of unaffordability of flood risk property-level adaptation measures across Europe using two definitions of affordability, which are combined with two different affordability thresholds from within flood risk research. It uses concepts of investment and payment affordability, with affordability thresholds based on residual income and expenditure definitions of unaffordability. These concepts, in turn, are linked with social justice through fairness concerns, in that, all should have equal capability to act, of which affordability is one avenue. In doing so, it was found that, for a large proportion of Europe, property owners generally cannot afford to make one-time payment of the cost of protective measures. These can be made affordable with installment payment mechanisms or similar mechanisms that spread costs over time. Therefore, the movement toward greater obligations for flood-prone residents to actively adapt to flooding should be accompanied by socially accessible financing mechanisms.
KW  - Affordability
KW  - flood risk
KW  - social justice
KW  - risk reduction
Y1  - 2020
U6  - https://doi.org/10.1111/risa.13465
SN  - 0272-4332
SN  - 1539-6924
VL  - 40
IS  - 6
SP  - 1151
EP  - 1167
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Crisologo, Irene
A1  - Heistermann, Maik
T1  - Using ground radar overlaps to verify the retrieval of calibration bias estimates from spaceborne platforms
JF  - Atmospheric measurement techniques : an interactive open access journal of the European Geosciences Union
N2  - Many institutions struggle to tap into the potential of their large archives of radar reflectivity: these data are often affected by miscalibration, yet the bias is typically unknown and temporally volatile. Still, relative calibration techniques can be used to correct the measurements a posteriori. For that purpose, the usage of spaceborne reflectivity observations from the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) platforms has become increasingly popular: the calibration bias of a ground radar (GR) is estimated from its average reflectivity difference to the spaceborne radar (SR). Recently, Crisologo et al. (2018) introduced a formal procedure to enhance the reliability of such estimates: each match between SR and GR observations is assigned a quality index, and the calibration bias is inferred as a quality-weighted average of the differences between SR and GR. The relevance of quality was exemplified for the Subic S-band radar in the Philippines, which is greatly affected by partial beam blockage. The present study extends the concept of quality-weighted averaging by accounting for path-integrated attenuation (PIA) in addition to beam blockage. This extension becomes vital for radars that operate at the C or X band. Correspondingly, the study setup includes a C-band radar that substantially overlaps with the S-band radar. Based on the extended quality-weighting approach, we retrieve, for each of the two ground radars, a time series of calibration bias estimates from suitable SR overpasses. As a result of applying these estimates to correct the ground radar observations, the consistency between the ground radars in the region of overlap increased substantially. Furthermore, we investigated if the bias estimates can be interpolated in time, so that ground radar observations can be corrected even in the absence of prompt SR overpasses. We found that a moving average approach was most suitable for that purpose, although limited by the absence of explicit records of radar maintenance operations.
Y1  - 2020
U6  - https://doi.org/10.5194/amt-13-645-2020
SN  - 1867-1381
SN  - 1867-8548
VL  - 13
IS  - 2
SP  - 645
EP  - 659
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Brunello, Camilla Francesca
A1  - Andermann, Christoff
A1  - Marc, Odin
A1  - Schneider, Katharina A.
A1  - Comiti, Francesco
A1  - Achleitner, Stefan
A1  - Hovius, Niels
T1  - Annually resolved monsoon onset and withdrawal dates across the Himalayas derived from local precipitation statistics
JF  - Geophysical research letters
N2  - A local and flexible definition of the monsoon season based on hydrological evidence is important for the understanding and management of Himalayan water resources. Here, we present an objective statistical method to retrieve seasonal hydrometeorological transitions. Applied to daily rainfall data (1951-2015), this method shows an average longitudinal delay of similar to 15 days, with later monsoon onset and earlier withdrawal in the western Himalaya, consistent with the continental progression of wet air masses. This delay leads to seasons of different length along the Himalaya and biased precipitation amounts when using uniform calendric monsoon boundaries. In the Central Himalaya annual precipitation has increased, due primarily to an increase of premonsoon precipitation. These findings highlight issues associated with a static definition of monsoon boundaries and call for a deeper understanding of nonmonsoonal precipitation over the Himalayan water tower. <br /> Plain Language Summary Precipitation in the Himalayas determines water availability for the Indian foreland with large socioeconomic implications. Despite its importance, spatial and temporal patterns of precipitation are poorly understood. Here, we estimate the long-term average and trends of seasonal precipitation at the scale of individual catchments draining the Himalayas. We apply a statistical method to detect the timing of hydrometeorological seasons from local precipitation measurements, focusing on monsoon onset and withdrawal. We identify longitudinal and latitudinal delays, resulting in seasons of different length along and across the Himalayas. These spatial patterns and the annual variability of the monsoon boundaries mean that oft-used, fixed calendric dates, for example, 1 June to 30 September, may be inadequate for retrieving monsoon rainfall totals. Moreover, we find that, despite its prominent contribution to annual rainfall totals, the Indian summer monsoon cannot explain the increase of the annual precipitation over the Central Himalayas. Instead, this appears to be mostly driven by changes in premonsoon and winter rainfall. So far, little attention has been paid to premonsoon precipitation, but governed by evaporative processes and surface water availability, it may be enhanced by irrigation and changed land use in the Gangetic foreland.
Y1  - 2020
U6  - https://doi.org/10.1029/2020GL088420
SN  - 0094-8276
SN  - 1944-8007
VL  - 47
IS  - 23
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Olen, Stephanie M.
A1  - Bookhagen, Bodo
T1  - Applications of SAR interferometric coherence time series
BT  - satiotemporal dynamics of geomorphic transitions in the South-Central Andes
JF  - Journal of geophysical research : Earth surface
N2  - Sediment transport domains in mountain landscapes are characterized by fundamentally different processes and rates depending on several factors, including geology, climate, and biota. Accurately identifying where transitions between transport domains occur is an important step to quantify the past, present, and future contribution of varying erosion and sedimentation processes and enhance our predictive capabilities. We propose a new methodology based on time series of synthetic aperture radar (SAR) interferometric coherence images to map sediment transport regimes across arid and semiarid landscapes. Using 4 years of Sentinel-1 data, we analyze sediment transport regimes for the south-central Andes in northwestern Argentina characterized by steep topographic and climatic gradients. We observe seasonally low coherence during the regional wet season, particularly on hillslopes and in alluvial channels. The spatial distribution of coherence is compared to drainage areas extracted from digital topography to identify two distinct transitions within watersheds: (a) a hillslope-to-fluvial and (b) a fluvial-to-alluvial transition. While transitions within a given basin can be well-constrained, the relative role of each sediment transport domain varies widely over the climatic and topographic gradients. In semiarid regions, we observe larger relative contributions from hillslopes compared to arid regions. Across regional gradients, the range of coherence within basins positively correlates to previously published millennial catchment-wide erosion rates and to topographic metrics used to indicate long-term uplift. Our study suggests that a dense time series of interferometric coherence can be used as a proxy for surface sediment movement and landscape stability in vegetation-free settings at event to decadal timescales.
KW  - Copernicus
KW  - SAR
KW  - critical infrastructure resilience
KW  - early warning
KW  - landslides
Y1  - 2020
U6  - https://doi.org/10.1029/2019JF005141
SN  - 2169-9003
SN  - 2169-9011
VL  - 125
IS  - 3
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Govin, Gwladys
A1  - van der Beek, Pieter A.
A1  - Najman, Yani
A1  - Millar, Ian
A1  - Gemignani, Lorenzo
A1  - Huyghe, Pascale
A1  - Dupont-Nivet, Guillaume
A1  - Bernet, Matthias
A1  - Mark, Chris
A1  - Wijbrans, Jan
T1  - Early onset and late acceleration of rapid exhumation in the Namche Barwa syntaxis, eastern Himalaya
JF  - Geology
N2  - The Himalayan syntaxes, characterized by extreme rates of rock exhumation co-located with major trans-orogenic rivers, figure prominently in the debate on tectonic versus erosional forcing of exhumation. Both the mechanism and timing of rapid exhumation of the Namche Barwa massif in the eastern syntaxis remain controversial. It has been argued that coupling between crustal rock advection and surface erosion initiated in the late Miocene (8-10 Ma). Recent studies, in contrast, suggest a Quaternary onset of rapid exhumation linked to a purely tectonic mechanism. We report new multisystem detrital thermochronology data from the most proximal Neogene clastic sediments downstream of Namche Barwa and use a thermo-kinematic model constrained by new and published data to explore its exhumation history. Modeling results show that exhumation accelerated to similar to 4 km/m.y. at ca. 8 Ma and to similar to 9 km/m.y. after ca. 2 Ma. This three-stage history reconciles apparently contradictory evidence for early and late onset of rapid exhumation and suggests efficient coupling between tectonics and erosion since the late Miocene. Quaternary acceleration of exhumation is consistent with river-profile evolution and may be linked to a Quaternary river-capture event.
Y1  - 2020
U6  - https://doi.org/10.1130/G47720.1
SN  - 0091-7613
SN  - 1943-2682
VL  - 48
IS  - 12
SP  - 1139
EP  - 1143
PB  - American Institute of Physics
CY  - Boulder
ER  - 
TY  - JOUR
A1  - Paprotny, Dominik
A1  - Kreibich, Heidi
A1  - Morales-Napoles, Oswaldo
A1  - Wagenaar, Dennis
A1  - Castellarin, Attilio
A1  - Carisi, Francesca
A1  - Bertin, Xavier
A1  - Merz, Bruno
A1  - Schröter, Kai
T1  - A probabilistic approach to estimating residential losses from different flood types
JF  - Natural hazards : journal of the International Society for the Prevention and Mitigation of Natural Hazards
N2  - Residential assets, comprising buildings and household contents, are a major source of direct flood losses. Existing damage models are mostly deterministic and limited to particular countries or flood types. Here, we compile building-level losses from Germany, Italy and the Netherlands covering a wide range of fluvial and pluvial flood events. Utilizing a Bayesian network (BN) for continuous variables, we find that relative losses (i.e. loss relative to exposure) to building structure and its contents could be estimated with five variables: water depth, flow velocity, event return period, building usable floor space area and regional disposable income per capita. The model's ability to predict flood losses is validated for the 11 flood events contained in the sample. Predictions for the German and Italian fluvial floods were better than for pluvial floods or the 1993 Meuse river flood. Further, a case study of a 2010 coastal flood in France is used to test the BN model's performance for a type of flood not included in the survey dataset. Overall, the BN model achieved better results than any of 10 alternative damage models for reproducing average losses for the 2010 flood. An additional case study of a 2013 fluvial flood has also shown good performance of the model. The study shows that data from many flood events can be combined to derive most important factors driving flood losses across regions and time, and that resulting damage models could be applied in an open data framework.
KW  - fluvial floods
KW  - coastal floods
KW  - pluvial floods
KW  - Bayesian networks
KW  - flood
KW  - damage surveys
Y1  - 2020
U6  - https://doi.org/10.1007/s11069-020-04413-x
SN  - 0921-030X
SN  - 1573-0840
VL  - 105
IS  - 3
SP  - 2569
EP  - 2601
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Racano, Simone
A1  - Jara Muñoz, Julius
A1  - Cosentino, Domenico
A1  - Melnick, Daniel
T1  - Variable quaternary uplift along the Southern Margin of the Central Anatolian Plateau inferred from modeling Marine Terrace sequences
JF  - Tectonics
N2  - The southern margin of the Central Anatolian Plateau (CAP) records a strong uplift phase after the early Middle Pleistocene, which has been related to the slab break-off of the subducting Arabian plate beneath the Anatolian microplate. During the last 450 kyr the area underwent an uplift phase at a mean rate of similar to 3.2 m/kyr, as suggested by Middle Pleistocene marine sediments exposed at similar to 1,500 m above sea level. These values are significantly higher than the 1.0-1.5 m/kyr estimated since the Late Pleistocene, suggesting temporal variations in uplift rate. To estimate changes in uplift rate during the Pleistocene we studied the marine terraces along the CAP southern margin, mapping the remnants of the platforms and their associated deposits in the field, and used the TerraceM software to identify the position and elevation of associated shoreline angles. We used shoreline angles and the timing of Quaternary marine sedimentation as constrains for a Landscape Evolution Model that simulates wave erosion of an uplifting coast. We applied random optimization algorithms and minimization statistics to find the input parameters that better reproduce the morphology of CAP marine terraces. The best-fitting uplift rate history suggests a significative increase from 1.9 to 3.5 m/kyr between 500 and 200 kyr, followed by an abrupt decrease to 1.4 m/kyr until the present. Our results agree with slab break-off models, which suggest a strong uplift pulse during slab rupture followed by a smoother decrease.
Y1  - 2020
U6  - https://doi.org/10.1029/2019TC005921
SN  - 0278-7407
SN  - 1944-9194
VL  - 39
IS  - 12
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ziebarth, Malte J.
A1  - von Specht, Sebastian
A1  - Heidbach, Oliver
A1  - Cotton, Fabrice
A1  - Anderson, John G.
T1  - Applying conservation of energy to estimate earthquake frequencies from strain rates and stresses
JF  - Journal of geophysical research : Solid earth
N2  - Estimating earthquake occurrence rates from the accumulation rate of seismic moment is an established tool of seismic hazard analysis. We propose an alternative, fault-agnostic approach based on the conservation of energy: the Energy-Conserving Seismicity Framework (ENCOS). Working in energy space has the advantage that the radiated energy is a better predictor of the damage potential of earthquake waves than the seismic moment release. In a region, ENCOS balances the stationary power available to cause earthquakes with the long-term seismic energy release represented by the energy-frequency distribution's first moment. Accumulation and release are connected through the average seismic efficiency, by which we mean the fraction of released energy that is converted into seismic waves. Besides measuring earthquakes in energy, ENCOS differs from moment balance essentially in that the energy accumulation rate depends on the total stress in addition to the strain rate tensor. To validate ENCOS, we exemplarily model the energy-frequency distribution around Southern California. We estimate the energy accumulation rate due to tectonic loading assuming poroelasticity and hydrostasis. Using data from the World Stress Map and assuming the frictional limit to estimate the stress tensor, we obtain a power of 0.8 GW. The uncertainty range, 0.3-2.0GW, originates mainly from the thickness of the seismogenic crust, the friction coefficient on preexisting faults, and models of Global Positioning System (GPS) derived strain rates. Based on a Gutenberg-Richter magnitude-frequency distribution, this power can be distributed over a range of energies consistent with historical earthquake rates and reasonable bounds on the seismic efficiency.
Y1  - 2020
U6  - https://doi.org/10.1029/2020JB020186
SN  - 2169-9313
SN  - 2169-9356
VL  - 125
IS  - 8
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Cheng, Chaojie
A1  - Milsch, Harald
T1  - Permeability variations in illite-bearing sandstone
BT  - effects of temperature and NaCl fluid salinity
JF  - Journal of geophysical research : Solid earth
N2  - Temperature changes and variations in pore fluid salinity may negatively affect the permeability of clay-bearing sandstones with implications for natural fluid flow and geotechnical applications alike. In this study these factors are investigated for a sandstone dominated by illite as the clay phase. Systematic long-term flow-through experiments were conducted and complemented with comprehensive microstructural investigations and the application of Derjaguin-Landau-Verwey-Overbeek (DLVO) theory to explain mechanistically the observed permeability changes. Initially, sample permeability was not affected by low pore fluid salinity indicating strong attraction of the illite particles to the pore walls as supported by electron microprobe analysis (EMPA). Increasing temperature up to 145 degrees C resulted in an irreversible permeability decrease by 1.5 orders of magnitude regardless of the pore fluid composition (i.e., deionized water and 2 M NaCl solution). Subsequently diluting the high salinity pore fluid to below 0.5 M yielded an additional permeability decline by 1.5 orders of magnitude, both at 145 degrees C and after cooling to room temperature. By applying scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) thermo-mechanical pore throat closure and illite particle migration were identified as independently operating mechanisms responsible for observed permeability changes during heating and dilution, respectively. These observations indicate that permeability of illite-bearing sandstones will be impaired by heating and exposure to low salinity pore fluids. In addition, chemically induced permeability variations proved to be path dependent with respect to the applied succession of fluid salinity changes.
Y1  - 2020
U6  - https://doi.org/10.1029/2020JB020122
SN  - 2169-9313
SN  - 2169-9356
VL  - 125
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Pilz, Tobias
A1  - Francke, Till
A1  - Baroni, Gabriele
A1  - Bronstert, Axel
T1  - How to Tailor my process-based hydrological model?
BT  - dynamic identifiability analysis of flexible model structures
JF  - Water resources research
N2  - In the field of hydrological modeling, many alternative representations of natural processes exist. Choosing specific process formulations when building a hydrological model is therefore associated with a high degree of ambiguity and subjectivity. In addition, the numerical integration of the underlying differential equations and parametrization of model structures influence model performance. Identifiability analysis may provide guidance by constraining the a priori range of alternatives based on observations. In this work, a flexible simulation environment is used to build an ensemble of semidistributed, process-based hydrological model configurations with alternative process representations, numerical integration schemes, and model parametrizations in an integrated manner. The flexible simulation environment is coupled with an approach for dynamic identifiability analysis. The objective is to investigate the applicability of the framework to identify the most adequate model. While an optimal model configuration could not be clearly distinguished, interesting results were obtained when relating model identifiability with hydro-meteorological boundary conditions. For instance, we tested the Penman-Monteith and Shuttleworth & Wallace evapotranspiration models and found that the former performs better under wet and the latter under dry conditions. Parametrization of model structures plays a dominant role as it can compensate for inadequate process representations and poor numerical solvers. Therefore, it was found that numerical solvers of high order of accuracy do often, though not necessarily, lead to better model performance. The proposed coupled framework proved to be a straightforward diagnostic tool for model building and hypotheses testing and shows potential for more in-depth analysis of process implementations and catchment functioning.
KW  - identifiability analysis
KW  - flexible model
KW  - numerics
KW  - model structure
KW  - WASA-SED
KW  - ECHSE
Y1  - 2020
U6  - https://doi.org/10.1029/2020WR028042
SN  - 0043-1397
SN  - 1944-7973
VL  - 56
IS  - 8
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Dahm, Torsten
A1  - Stiller, Manfred
A1  - Mechie, James
A1  - Heimann, Sebastian
A1  - Hensch, Martin
A1  - Woith, Heiko
A1  - Schmidt, Bernd
A1  - Gabriel, Gerald
A1  - Weber, Michael
T1  - Seismological and geophysical signatures of the deep crustal magma systems of the cenozoic volcanic fields Beneath the Eifel, Germany
JF  - Geochemistry, geophysics, geosystems
N2  - The Quaternary volcanic fields of the Eifel (Rhineland-Palatinate, Germany) had their last eruptions less than 13,000 years ago. Recently, deep low-frequency (DLF) earthquakes were detected beneath one of the volcanic fields showing evidence of ongoing magmatic activity in the lower crust and upper mantle. In this work, seismic wide- and steep-angle experiments from 1978/1979 and 1987/1988 are compiled, partially reprocessed and interpreted, together with other data to better determine the location, size, shape, and state of magmatic reservoirs in the Eifel region near the crust-mantle boundary. We discuss seismic evidence for a low-velocity gradient layer from 30-36 km depth, which has developed over a large region under all Quaternary volcanic fields of the Rhenish Massif and can be explained by the presence of partial melts. We show that the DLF earthquakes connect the postulated upper mantle reservoir with the upper crust at a depth of about 8 km, directly below one of the youngest phonolitic volcanic centers in the Eifel, where CO(2)originating from the mantle is massively outgassing. A bright spot in the West Eifel between 6 and 10 km depth represents a Tertiary magma reservoir and is seen as a model for a differentiated reservoir beneath the young phonolitic center today. We find that the distribution of volcanic fields is controlled by the Variscan lithospheric structures and terrane boundaries as a whole, which is reflected by an offset of the Moho depth, a wedge-shaped transparent zone in the lower crust and the system of thrusts over about 120 km length.
KW  - magma reservoirs
KW  - distributed volcanic fields
KW  - reflection seismic
KW  - crustal magma chamber
KW  - deep low-frequency earthquakes
KW  - low velocity zone
Y1  - 2020
U6  - https://doi.org/10.1029/2020GC009062
SN  - 1525-2027
VL  - 21
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Baes, Marzieh
A1  - Sobolev, Stephan V.
A1  - Gerya, Taras V.
A1  - Brune, Sascha
T1  - Subduction initiation by Plume-Plateau interaction
BT  - insights from numerical models
JF  - Geochemistry, geophysics, geosystems
N2  - It has recently been demonstrated that the interaction of a mantle plume with sufficiently old oceanic lithosphere can initiate subduction. However, the existence of large lithospheric heterogeneities, such as a buoyant plateau, in proximity to a rising plume head may potentially hinder the formation of a new subduction zone. Here, we investigate this scenario by means of 3-D numerical thermomechanical modeling. We explore how plume-lithosphere interaction is affected by lithospheric age, relative location of plume head and plateau border, and the strength of the oceanic crust. Our numerical experiments suggest four different geodynamic regimes: (a) oceanic trench formation, (b) circular oceanic-plateau trench formation, (c) plateau trench formation, and (d) no trench formation. We show that regardless of the age and crustal strength of the oceanic lithosphere, subduction can initiate when the plume head is either below the plateau border or at a distance less than the plume radius from the plateau edge. Crustal heterogeneity facilitates subduction initiation of old oceanic lithosphere. High crustal strength hampers the formation of a new subduction zone when the plume head is located below a young lithosphere containing a thick and strong plateau. We suggest that plume-plateau interaction in the western margin of the Caribbean could have resulted in subduction initiation when the plume head impinged onto the oceanic lithosphere close to the border between plateau and oceanic crust.
KW  - subduction zone
KW  - plume
KW  - plateau
KW  - numerical modeling
KW  - plume-induced
KW  - subduction initiation (PISI)
Y1  - 2020
U6  - https://doi.org/10.1029/2020GC009119
SN  - 1525-2027
VL  - 21
IS  - 8
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schoppa, Lukas
A1  - Sieg, Tobias
A1  - Vogel, Kristin
A1  - Zöller, Gert
A1  - Kreibich, Heidi
T1  - Probabilistic flood loss models for companies
JF  - Water resources research
N2  - Flood loss modeling is a central component of flood risk analysis. Conventionally, this involves univariable and deterministic stage-damage functions. Recent advancements in the field promote the use of multivariable and probabilistic loss models, which consider variables beyond inundation depth and account for prediction uncertainty. Although companies contribute significantly to total loss figures, novel modeling approaches for companies are lacking. Scarce data and the heterogeneity among companies impede the development of company flood loss models. We present three multivariable flood loss models for companies from the manufacturing, commercial, financial, and service sector that intrinsically quantify prediction uncertainty. Based on object-level loss data (n = 1,306), we comparatively evaluate the predictive capacity of Bayesian networks, Bayesian regression, and random forest in relation to deterministic and probabilistic stage-damage functions, serving as benchmarks. The company loss data stem from four postevent surveys in Germany between 2002 and 2013 and include information on flood intensity, company characteristics, emergency response, private precaution, and resulting loss to building, equipment, and goods and stock. We find that the multivariable probabilistic models successfully identify and reproduce essential relationships of flood damage processes in the data. The assessment of model skill focuses on the precision of the probabilistic predictions and reveals that the candidate models outperform the stage-damage functions, while differences among the proposed models are negligible. Although the combination of multivariable and probabilistic loss estimation improves predictive accuracy over the entire data set, wide predictive distributions stress the necessity for the quantification of uncertainty.
KW  - flood loss estimation
KW  - probabilistic modeling
KW  - companies
KW  - multivariable
KW  - models
Y1  - 2020
U6  - https://doi.org/10.1029/2020WR027649
SN  - 0043-1397
SN  - 1944-7973
VL  - 56
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Muldashev, Iskander A.
A1  - Sobolev, Stephan
T1  - What controls maximum magnitudes of giant subduction earthquakes?
JF  - Geochemistry, geophysics, geosystems
N2  - Giant earthquakes with magnitudes above 8.5 occur only in subduction zones. Despite the developments made in observing large subduction zone earthquakes with geophysical instruments, the factors controlling the maximum size of these earthquakes are still poorly understood. Previous studies have suggested the importance of slab shape, roughness of the plate interface contact, state of the strain in the upper plate, thickness of sediments filling the trenches, and subduction rate. Here, we present 2-D cross-scale numerical models of seismic cycles for subduction zones with various geometries, subduction channel friction configurations, and subduction rates. We found that low-angle subduction and thick sediments in the subduction channel are the necessary conditions for generating giant earthquakes, while the subduction rate has a negligible effect. We suggest that these key parameters determine the maximum magnitude of a subduction earthquake by controlling the seismogenic zone width and smoothness of the subduction interface. This interpretation supports previous studies that are based upon observations and scaling laws. Our modeling results also suggest that low static friction in the sediment-filled subduction channel results in neutral or moderate compressive deformation in the overriding plate for low-angle subduction zones hosting giant earthquakes. These modeling results agree well with observations for the largest earthquakes. Based on our models we predict maximum magnitudes of subduction earthquakes worldwide, demonstrating the fit to magnitudes of all giant earthquakes of the 20th and 21st centuries and good agreement with the predictions based on statistical analyses of observations.
KW  - giant earthquakes
KW  - earthquake modeling
KW  - subduction
Y1  - 2020
U6  - https://doi.org/10.1029/2020GC009145
SN  - 1525-2027
VL  - 21
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Sharma, Shubham
A1  - Hainzl, Sebastian
A1  - Zöller, Gert
A1  - Holschneider, Matthias
T1  - Is Coulomb stress the best choice for aftershock forecasting?
JF  - Journal of geophysical research : Solid earth
N2  - The Coulomb failure stress (CFS) criterion is the most commonly used method for predicting spatial distributions of aftershocks following large earthquakes. However, large uncertainties are always associated with the calculation of Coulomb stress change. The uncertainties mainly arise due to nonunique slip inversions and unknown receiver faults; especially for the latter, results are highly dependent on the choice of the assumed receiver mechanism. Based on binary tests (aftershocks yes/no), recent studies suggest that alternative stress quantities, a distance-slip probabilistic model as well as deep neural network (DNN) approaches, all are superior to CFS with predefined receiver mechanism. To challenge this conclusion, which might have large implications, we use 289 slip inversions from SRCMOD database to calculate more realistic CFS values for a layered half-space and variable receiver mechanisms. We also analyze the effect of the magnitude cutoff, grid size variation, and aftershock duration to verify the use of receiver operating characteristic (ROC) analysis for the ranking of stress metrics. The observations suggest that introducing a layered half-space does not improve the stress maps and ROC curves. However, results significantly improve for larger aftershocks and shorter time periods but without changing the ranking. We also go beyond binary testing and apply alternative statistics to test the ability to estimate aftershock numbers, which confirm that simple stress metrics perform better than the classic Coulomb failure stress calculations and are also better than the distance-slip probabilistic model.
Y1  - 2020
U6  - https://doi.org/10.1029/2020JB019553
SN  - 2169-9313
SN  - 2169-9356
VL  - 125
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kaya, Mustafa Yuecel
A1  - Dupont-Nivet, Guillaume
A1  - Proust, Jean-Noël
A1  - Roperch, Pierrick
A1  - Meijer, Niels
A1  - Frieling, Joost
A1  - Fioroni, Chiara
A1  - Altiner, Sevinç Özkan
A1  - Stoica, Marius
A1  - Aminov, Jovid
A1  - Mamtimin, Mehmut
A1  - Guo, Zhaojie
T1  - Cretaceous evolution of the Central Asian Proto-Paratethys Sea
BT  - tectonic, eustatic, and climatic controls
JF  - Tectonics
N2  - The timing and mechanisms of the Cretaceous sea incursions into Central Asia are still poorly constrained. We provide a new chronostratigraphic framework based on biostratigraphy and magnetostratigraphy together with detailed paleoenvironmental analyses of Cretaceous records of the proto-Paratethys Sea fluctuations in the Tajik and Tarim basins. The Early Cretaceous marine incursion in the western Tajik Basin was followed by major marine incursions during the Cenomanian (ca. 100 Ma) and Santonian (ca. 86 Ma) that reached far into the eastern Tajik and Tarim basins. These marine incursions were separated by a Turonian-Coniacian (ca. 92-86 Ma) regression. Basin-wide tectonic subsidence analyses imply that the Early Cretaceous sea incursion into the Tajik Basin was related to increased Pamir tectonism. We find that thrusting along the northern edge of the Pamir at ca. 130-90 Ma resulted in increased subsidence in a retro-arc basin setting. This tectonic event and coeval eustatic highstand resulted in the maximum observed geographic extent of the sea during the Cenomanian (ca. 100 Ma). The following Turonian-Coniacian (ca. 92-86 Ma) major regression, driven by eustasy, coincides with a sharp slowdown in tectonic subsidence during the late orogenic unloading period with limited thrusting. The Santonian (ca. 86 Ma) major sea incursion was likely controlled by eustasy as evidenced by the coeval fluctuations in the west Siberian Basin. An early Maastrichtian cooling (ca. 71-70 Ma), potentially connected to global Late Cretaceous trends, is inferred from the replacement of mollusk-rich limestones by bryozoan- and echinoderm-rich limestones.
Y1  - 2020
U6  - https://doi.org/10.1029/2019TC005983
SN  - 0278-7407
SN  - 1944-9194
VL  - 39
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ladeira, Guenia
A1  - Marwan, Norbert
A1  - Destro-Filho, Joao-Batista
A1  - Ramos, Camila Davi
A1  - Lima, Gabriela
T1  - Frequency spectrum recurrence analysis
JF  - Scientific reports
N2  - In this paper, we present the new frequency spectrum recurrence analysis technique by means of electro-encephalon signals (EES) analyses. The technique is suitable for time series analysis with noise and disturbances. EES were collected, and alpha waves of the occipital region were analysed by comparing the signals from participants in two states, eyes open and eyes closed. Firstly, EES were characterized and analysed by means of techniques already known to compare with the results of the innovative technique that we present here. We verified that, standard recurrence quantification analysis by means of EES time series cannot statistically distinguish the two states. However, the new frequency spectrum recurrence quantification exhibit quantitatively whether the participants have their eyes open or closed. In sequence, new quantifiers are created for analysing the recurrence concentration on frequency bands. These analyses show that EES with similar frequency spectrum have different recurrence levels revealing different behaviours of the nervous system. The technique can be used to deepen the study on depression, stress, concentration level and other neurological issues and also can be used in any complex system.
KW  - Biomedical engineering
KW  - Brain injuries
KW  - Computational models
KW  - Computational neuroscience
KW  - Data acquisition
KW  - Data processing
KW  - Electrical and electronic engineering
KW  - Neural circuits
KW  - Visual system
Y1  - 2020
U6  - https://doi.org/10.1038/s41598-020-77903-4
SN  - 2045-2322
VL  - 10
IS  - 1
PB  - Nature portfolio
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Soares, Gabriel Brando
A1  - Yamazaki, Yosuke
A1  - Cnossen, Ingrid
A1  - Matzka, Jürgen
A1  - Pinheiro, Katia J.
A1  - Morschhauser, Achim
A1  - Alken, Patrick
A1  - Stolle, Claudia
T1  - Evolution of the geomagnetic daily variation at Tatuoca, Brazil, From 1957 to 2019
BT  - a transition from Sq to EEJ
JF  - Journal of geophysical research : Space physics
N2  - The magnetic equator in the Brazilian region has moved over 1,100 km northward since 1957, passing the geomagnetic observatory Tatuoca (TTB), in northern Brazil, around 2013. We recovered and processed TTB hourly mean values of the geomagnetic field horizontal (H) component from 1957 until 2019, allowing the investigation of long-term changes in the daily variation due to the influence of secular variation, solar activity, season, and lunar phase. The H day-to-day variability and the occurrence of the counter electrojet at TTB were also investigated. Until the 1990s, ionospheric solar quiet currents dominated the quiet-time daily variation at TTB. After 2000, the magnitude of the daily variation became appreciably greater due to the equatorial electrojet (EEJ) contribution. The H seasonal and day-to-day variability increased as the magnetic equator approached, but their amplitudes normalized to the average daily variation remained at similar levels. Meanwhile, the amplitude of the lunar variation, normalized in the same way, increased from 5% to 12%. Within the EEJ region, the occurrence rate of the morning counter electrojet (MCEJ) increased with proximity to the magnetic equator, while the afternoon counter electrojet (ACEJ) did not. EEJ currents derived from CHAMP and Swarm satellite data revealed that the MCEJ rate varies with magnetic latitude within the EEJ region while the ACEJ rate is largely constant. Simulations with the Thermosphere-Ionosphere-Electrodynamics General Circulation Model based on different geomagnetic main field configurations suggest that long-term changes in the geomagnetic daily variation at TTB can be attributed to the main field secular variation.
Y1  - 2020
U6  - https://doi.org/10.1029/2020JA028109
SN  - 2169-9380
SN  - 2169-9402
VL  - 125
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Rodriguez Piceda, Constanza
A1  - Scheck Wenderoth, Magdalena
A1  - Gomez Dacal, Maria Laura
A1  - Bott, Judith
A1  - Prezzi, Claudia Beatriz
A1  - Strecker, Manfred
T1  - Lithospheric density structure of the southern Central Andes constrained by 3D data-integrative gravity modelling
JF  - International journal of earth sciences
N2  - The southern Central Andes (SCA) (between 27 degrees S and 40 degrees S) is bordered to the west by the convergent margin between the continental South American Plate and the oceanic Nazca Plate. The subduction angle along this margin is variable, as is the deformation of the upper plate. Between 33 degrees S and 35 degrees S, the subduction angle of the Nazca plate increases from sub-horizontal (< 5 degrees) in the north to relatively steep (similar to 30 degrees) in the south. The SCA contain inherited lithological and structural heterogeneities within the crust that have been reactivated and overprinted since the onset of subduction and associated Cenozoic deformation within the Andean orogen. The distribution of the deformation within the SCA has often been attributed to the variations in the subduction angle and the reactivation of these inherited heterogeneities. However, the possible influence that the thickness and composition of the continental crust have had on both short-term and long-term deformation of the SCA is yet to be thoroughly investigated. For our investigations, we have derived density distributions and thicknesses for various layers that make up the lithosphere and evaluated their relationships with tectonic events that occurred over the history of the Andean orogeny and, in particular, investigated the short- and long-term nature of the present-day deformation processes. We established a 3D model of lithosphere beneath the orogen and its foreland (29 degrees S-39 degrees S) that is consistent with currently available geological and geophysical data, including the gravity data. The modelled crustal configuration and density distribution reveal spatial relationships with different tectonic domains: the crystalline crust in the orogen (the magmatic arc and the main orogenic wedge) is thicker (similar to 55 km) and less dense (similar to 2900 kg/m(3)) than in the forearc (similar to 35 km, similar to 2975 kg/m(3)) and foreland (similar to 30 km, similar to 3000 kg/m(3)). Crustal thickening in the orogen probably occurred as a result of stacking of low-density domains, while density and thickness variations beneath the forearc and foreland most likely reflect differences in the tectonic evolution of each area following crustal accretion. No clear spatial relationship exists between the density distribution within the lithosphere and previously proposed boundaries of crustal terranes accreted during the early Paleozoic. Areas with ongoing deformation show a spatial correlation with those areas that have the highest topographic gradients and where there are abrupt changes in the average crustal-density contrast. This suggests that the short-term deformation within the interior of the Andean orogen and its foreland is fundamentally influenced by the crustal composition and the relative thickness of different crustal layers. A thicker, denser, and potentially stronger lithosphere beneath the northern part of the SCA foreland is interpreted to have favoured a strong coupling between the Nazca and South American plates, facilitating the development of a sub-horizontal slab.
KW  - Central andes
KW  - Lithospheric structure
KW  - Crustal density
KW  - Gravity
KW  - modelling
KW  - Subduction
Y1  - 2020
U6  - https://doi.org/10.1007/s00531-020-01962-1
SN  - 1437-3254
SN  - 1437-3262
VL  - 110
IS  - 7
SP  - 2333
EP  - 2359
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Ghani, Humaad
A1  - Sobel, Edward
A1  - Zeilinger, Gerold
A1  - Glodny, Johannes
A1  - Zapata, Sebastian
A1  - Irum, Irum
T1  - Palaeozoic and Pliocene tectonic evolution of the Salt Range constrained by low-temperature thermochronology
JF  - Terra nova
N2  - The Salt Range in Pakistan exposes Precambrian to Pleistocene strata outcropping along the Salt Range Thrust (SRT). To better understand the in-situ Cambrian and Pliocene tectonic evolution of the Pakistan Subhimalaya, we have conducted low-temperature thermochronological analysis using apatite (U-Th-Sm)/He and fission track dating. We combine cooling ages from different samples located along the thrust front of the SRT into a thermal model that shows two major cooling events associated with rifting and regional erosion in the Late Palaeozoic and SRT activity since the Pliocene. Our results suggest that the SRT maintained a long-term average shortening rate of similar to 5-6 mm/yr and a high exhumation rate above the SRT ramp since similar to 4 Ma.
KW  - exhumation
KW  - fault bend fold
KW  - ramp
KW  - Salt Range
Y1  - 2020
U6  - https://doi.org/10.1111/ter.12515
SN  - 0954-4879
SN  - 1365-3121
VL  - 33
IS  - 3
SP  - 293
EP  - 305
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Stich, Daniel
A1  - Martin, Rosa
A1  - Morales, Jose
A1  - Lopez-Comino, Jose Angel
A1  - Mancilla, Flor de Lis
T1  - Slip partitioning in the 2016 Alboran Sea earthquake sequence (western Mediterranean)
JF  - Frontiers in Earth Science
N2  - AM(W)= 5.1 earthquake on January 21st, 2016 marked the beginning of a significant seismic sequence in the southern Alboran Sea, culminating in aM(W)= 6.3 earthquake on January 25th, and continuing with further moderate magnitude earthquakes until March. We use data from 35 seismic broadband stations in Spain, Morocco and Portugal to relocate the seismicity, estimate seismic moment tensors, and isolate regional apparent source time functions for the main earthquake. Relocation and regional moment tensor inversion consistently yield very shallow depths for the majority of events. We obtain 50 moment tensors for the sequence, showing a mixture of strike-slip faulting for the foreshock and the main event and reverse faulting for the major aftershocks. The leading role of reverse focal mechanisms among the aftershocks may be explained by the geometry of the fault network. The mainshock nucleates at a bend along the left-lateral Al-Idrisi fault, introducing local transpression within the transtensional Alboran Basin. The shallow depths of the 2016 Alboran Sea earthquakes may favor slip-partitioning on the involved faults. Apparent source durations for the main event suggest a similar to 21 km long, asymmetric rupture that propagates primarily toward NE into the restraining fault segment, with fast rupture speed of similar to 3.0 km/s. Consistently, the inversion for laterally variable fault displacement situates the main slip in the restraining segment. The partitioning into strike-slip rupture and dip-slip aftershocks confirms a non-optimal orientation of this segment, and suggests that the 2016 event settled a slip deficit from previous ruptures that could not propagate into the stronger restraining segment.
KW  - slip partitioning
KW  - fault bend
KW  - moment tensor
KW  - source time function
KW  - shallow earthquakes
Y1  - 2020
U6  - https://doi.org/10.3389/feart.2020.587356
SN  - 2296-6463
VL  - 8
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Angelopoulos, Michael
A1  - Overduin, Pier Paul
A1  - Westermann, Sebastian
A1  - Tronicke, Jens
A1  - Strauss, Jens
A1  - Schirrmeister, Lutz
A1  - Biskaborn, Boris
A1  - Liebner, Susanne
A1  - Maksimov, Georgii
A1  - Grigoriev, Mikhail N.
A1  - Grosse, Guido
T1  - Thermokarst lake to lagoon transitions in Eastern Siberia
BT  - do submerged taliks refreeze?
JF  - Journal of geophysical research : Earth surface
N2  - As the Arctic coast erodes, it drains thermokarst lakes, transforming them into lagoons, and, eventually, integrates them into subsea permafrost. Lagoons represent the first stage of a thermokarst lake transition to a marine setting and possibly more saline and colder upper boundary conditions. In this research, borehole data, electrical resistivity surveying, and modeling of heat and salt diffusion were carried out at Polar Fox Lagoon on the Bykovsky Peninsula, Siberia. Polar Fox Lagoon is a seasonally isolated water body connected to Tiksi Bay through a channel, leading to hypersaline waters under the ice cover. The boreholes in the center of the lagoon revealed floating ice and a saline cryotic bed underlain by a saline cryotic talik, a thin ice-bearing permafrost layer, and unfrozen ground. The bathymetry showed that most of the lagoon had bedfast ice in spring. In bedfast ice areas, the electrical resistivity profiles suggested that an unfrozen saline layer was underlain by a thick layer of refrozen talik. The modeling showed that thermokarst lake taliks can refreeze when submerged in saltwater with mean annual bottom water temperatures below or slightly above 0 degrees C. This occurs, because the top-down chemical degradation of newly formed ice-bearing permafrost is slower than the refreezing of the talik. Hence, lagoons may precondition taliks with a layer of ice-bearing permafrost before encroachment by the sea, and this frozen layer may act as a cap on gas migration out of the underlying talik.
KW  - thermokarst lake
KW  - talik
KW  - lagoon
KW  - subsea permafrost
KW  - salt diffusion
KW  - Siberia
Y1  - 2020
U6  - https://doi.org/10.1029/2019JF005424
SN  - 2169-9003
SN  - 2169-9011
VL  - 125
IS  - 10
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ou, Qi
A1  - Kulikova, Galina
A1  - Yu, Jingxing
A1  - Elliott, Austin
A1  - Parsons, Bethany
A1  - Walker, Richard
T1  - Magnitude of the 1920 Haiyuan earthquake reestimated using seismological and geomorphological methods
JF  - Journal of geophysical research : Solid earth
N2  - Reported magnitudes ranging between 7.8 and 8.7 highlight a confusion about the true size of the 1920 Haiyuan earthquake, the largest earthquake recorded in the northeast Tibetan Plateau. We compiled a global data set of previously unlooked-at historical seismograms and performed modern computational analyses on the digitized seismic records. We found the epicenter to be near Haiyuan town and obtained a moment magnitude of M-W=7.90.2. Following traditional approaches, we obtained m(B)=7.90.3 with data from 21 stations and M-S(20)=8.10.2 with data from three stations. Geomorphologically, we mapped the surface rupture and horizontal offsets on high-resolution Pleiades satellite and drone imagery that covered the entire western and middle sections of the 1920 Haiyuan earthquake rupture and compiled offsets reported on the eastern section from field measurements in the 1980s. Careful discrimination between single-event and cumulative offsets suggests average horizontal slips of 3.01.0m on the western section, 4.51.5m on the middle section, and 3.5 +/- 0.5m on the eastern section, indicating a total moment magnitude of M-W=7.8 +/- 0.1. Thus, the seismological and geomorphological results agree within the uncertainties, a weighted average giving a moment magnitude of M-W=7.9 +/- 0.2 for the 1920 Haiyuan earthquake. It is likely that earthquake magnitudes based on the historical M were systematically overestimated. <br /> Plain Language Summary Earthquakes are the main mechanism by which elastic energy accumulating due to tectonic motion is released. As the earthquake magnitude scale is logarithmic, major earthquakes control the bulk of this energy budget and are often the most destructive, like the 1920 Haiyuan earthquake with similar to 230,000 casualties. However, major earthquakes tend to have recurrence periods of several hundred years, longer than our instrumental records. To obtain knowledge of historic major earthquakes, paleoseismologists measure geomorphic offsets and map surface ruptures left by past events and estimate the shaking intensity from historical writings. However, in the case of the Haiyuan earthquake, which happened in the late historic, early instrumental period, the magnitudes reported from these two communities differed significantly. In order to constrain the magnitude of this earthquake for seismic hazard assessment and to reconcile the differences between published magnitudes, we reestimated its magnitude from both newly compiled and digitized seismological records and modern satellite and drone imagery. The results show that the early seismological magnitudes were overestimated, which may affect historical magnitudes systematically. The 1920 Haiyuan earthquake was of a similar magnitude to the 2001 Kokoxili and 2008 Wenchuan earthquakes that also occurred in and around the Tibetan Plateau, instead of more than half a magnitude larger.
Y1  - 2020
U6  - https://doi.org/10.1029/2019JB019244
SN  - 2169-9313
SN  - 2169-9356
VL  - 125
IS  - 8
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Giarolla, Emanuel
A1  - Veiga, Sandro F.
A1  - Nobre, Paulo
A1  - Silva, Manoel B.
A1  - Capistrano, Vinicius B.
A1  - Callegare, Andyara O.
T1  - Sea surface height trends in the southern hemisphere oceans simulated by the Brazilian Earth System Model under RCP4.5 and RCP8.5 scenarios
JF  - Journal of southern hemisphere earth systems science
N2  - The Brazilian Earth System Model (BESM-OA2.5), while simulating the historical period proposed by the fifth phase of the Coupled Model Intercomparison Project (CMIP5), detects an increasing trend in the sea surface height (SSH) on the southern hemisphere oceans relative to that of the pre-industrial era. The increasing trend is accentuated in the CMIP5 RCP4.5 and RCP8.5 future scenarios with higher concentrations of greenhouse gases in the atmosphere. This study sheds light on the sources of such trends in these regions. The results suggest an association with the thermal expansion of the oceans in the upper 700 m due to a gradual warming inflicted by those future scenarios. BESM-OA2.5 presents a surface height increase of 0.11 m in the historical period of 1850-2005. Concerning future projections, BESM-OA2.5 projects SSH increases of 0.14 and 0.23 m (relative to the historical 2005 value) for RCP4.5 and RCP8.5, respectively, by the end of 2100. These increases are predominantly in a band of latitude within 35-60 degrees S in the Atlantic and Indian oceans. The reproducibility of the trend signal detected in the BESM-OA2.5 simulations is confirmed by the results of three other CMIP5 models.
KW  - Brazilian Earth System Model
KW  - CMIP5
KW  - IPCC AR5 scenarios
KW  - RCP4.5
KW  - RCP8.5
KW  - sea level trends
KW  - sea surface height
KW  - southern hemisphere oceans
Y1  - 2020
U6  - https://doi.org/10.1071/ES19042
SN  - 2206-5865
VL  - 70
IS  - 1
SP  - 280
EP  - 289
PB  - CSIRO
CY  - Clayton
ER  - 
TY  - JOUR
A1  - Merz, Bruno
A1  - Kuhlicke, Christian
A1  - Kunz, Michael
A1  - Pittore, Massimiliano
A1  - Babeyko, Andrey
A1  - Bresch, David N.
A1  - Domeisen, Daniela I.
A1  - Feser, Frauke
A1  - Koszalka, Inga
A1  - Kreibich, Heidi
A1  - Pantillon, Florian
A1  - Parolai, Stefano
A1  - Pinto, Joaquim G.
A1  - Punge, Heinz Jürgen
A1  - Rivalta, Eleonora
A1  - Schröter, Kai
A1  - Strehlow, Karen
A1  - Weisse, Ralf
A1  - Wurpts, Andreas
T1  - Impact forecasting to support emergency management of natural hazards
JF  - Reviews of geophysics
N2  - Forecasting and early warning systems are important investments to protect lives, properties, and livelihood. While early warning systems are frequently used to predict the magnitude, location, and timing of potentially damaging events, these systems rarely provide impact estimates, such as the expected amount and distribution of physical damage, human consequences, disruption of services, or financial loss. Complementing early warning systems with impact forecasts has a twofold advantage: It would provide decision makers with richer information to take informed decisions about emergency measures and focus the attention of different disciplines on a common target. This would allow capitalizing on synergies between different disciplines and boosting the development of multihazard early warning systems. This review discusses the state of the art in impact forecasting for a wide range of natural hazards. We outline the added value of impact-based warnings compared to hazard forecasting for the emergency phase, indicate challenges and pitfalls, and synthesize the review results across hazard types most relevant for Europe.
KW  - impact forecasting
KW  - natural hazards
KW  - early warning
Y1  - 2020
U6  - https://doi.org/10.1029/2020RG000704
SN  - 8755-1209
SN  - 1944-9208
VL  - 58
IS  - 4
PB  - American Geophysical Union
CY  - Washington
ER  -