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
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  - 
TY  - JOUR
A1  - Marcisz, Katarzyna
A1  - Jassey, Vincent E. J.
A1  - Kosakyan, Anush
A1  - Krashevska, Valentyna
A1  - Lahr, Daniel J. G.
A1  - Lara, Enrique
A1  - Lamentowicz, Lukasz
A1  - Lamentowicz, Mariusz
A1  - Macumber, Andrew
A1  - Mazei, Yuri
A1  - Mitchell, Edward A. D.
A1  - Nasser, Nawaf A.
A1  - Patterson, R. Timothy
A1  - Roe, Helen M.
A1  - Singer, David
A1  - Tsyganov, Andrey N.
A1  - Fournier, Bertrand
T1  - Testate amoeba functional traits and their use in paleoecology
JF  - Frontiers in Ecology and Evolution
N2  - This review provides a synthesis of current knowledge on the morphological and functional traits of testate amoebae, a polyphyletic group of protists commonly used as proxies of past hydrological changes in paleoecological investigations from peatland, lake sediment and soil archives. A trait-based approach to understanding testate amoebae ecology and paleoecology has gained in popularity in recent years, with research showing that morphological characteristics provide complementary information to the commonly used environmental inferences based on testate amoeba (morpho-)species data. We provide a broad overview of testate amoeba morphological and functional traits and trait-environment relationships in the context of ecology, evolution, genetics, biogeography, and paleoecology. As examples we report upon previous ecological and paleoecological studies that used trait-based approaches, and describe key testate amoebae traits that can be used to improve the interpretation of environmental studies. We also highlight knowledge gaps and speculate on potential future directions for the application of trait-based approaches in testate amoeba research.
KW  - protists
KW  - functional traits
KW  - morphological traits
KW  - ecology
KW  - peatlands
KW  - lakes
KW  - soils
KW  - trait-based approaches
Y1  - 2020
U6  - https://doi.org/10.3389/fevo.2020.575966
SN  - 2296-701X
VL  - 8
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Rajaonarison, Tahiry A.
A1  - Stamps, D. Sarah
A1  - Fishwick, Stewart
A1  - Brune, Sascha
A1  - Glerum, Anne
A1  - Hu, Jiashun
T1  - Numerical modeling of mantle flow beneath Madagascar to constrain upper mantle rheology beneath continental regions
JF  - Journal of geophysical research : Solid earth
N2  - Over the past few decades, azimuthal seismic anisotropy measurements have been widely used proxy to study past and present-day deformation of the lithosphere and to characterize convection in the mantle. Beneath continental regions, distinguishing between shallow and deep sources of anisotropy remains difficult due to poor depth constraints of measurements and a lack of regional-scale geodynamic modeling. Here, we constrain the sources of seismic anisotropy beneath Madagascar where a complex pattern cannot be explained by a single process such as absolute plate motion, global mantle flow, or geology. We test the hypotheses that either Edge-Driven Convection (EDC) or mantle flow derived from mantle wind interactions with lithospheric topography is the dominant source of anisotropy beneath Madagascar. We, therefore, simulate two sets of mantle convection models using regional-scale 3-D computational modeling. We then calculate Lattice Preferred Orientation that develops along pathlines of the mantle flow models and use them to calculate synthetic splitting parameters. Comparison of predicted with observed seismic anisotropy shows a good fit in northern and southern Madagascar for the EDC model, but the mantle wind case only fits well in northern Madagascar. This result suggests the dominant control of the measured anisotropy may be from EDC, but the role of localized fossil anisotropy in narrow shear zones cannot be ruled out in southern Madagascar. Our results suggest that the asthenosphere beneath northern and southern Madagascar is dominated by dislocation creep. Dislocation creep rheology may be dominant in the upper asthenosphere beneath other regions of continental lithosphere.
KW  - seismic anisotropy
KW  - edge-driven convection
KW  - mantle flow modeling
KW  - lattice preferred orientations
KW  - lithosphere-mantle wind interactions
KW  - splitting parameters
Y1  - 2019
U6  - https://doi.org/10.1029/2019JB018560
SN  - 2169-9313
SN  - 2169-9356
VL  - 125
IS  - 2
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Tofelde, Stefanie
A1  - Bernhardt, Anne
A1  - Guerit, Laure
A1  - Romans, Brian W.
T1  - Times Associated With Source-to-Sink Propagation of Environmental Signals During Landscape Transience
JF  - Frontiers in Earth Science
N2  - Sediment archives in the terrestrial and marine realm are regularly analyzed to infer changes in climate, tectonic, or anthropogenic boundary conditions of the past. However, contradictory observations have been made regarding whether short period events are faithfully preserved in stratigraphic archives; for instance, in marine sediments offshore large river systems. On the one hand, short period events are hypothesized to be non-detectable in the signature of terrestrially derived sediments due to buffering during sediment transport along large river systems. On the other hand, several studies have detected signals of short period events in marine records offshore large river systems. We propose that this apparent discrepancy is related to the lack of a differentiation between different types of signals and the lack of distinction between river response times and signal propagation times. In this review, we (1) expand the definition of the term ‘signal’ and group signals in sub-categories related to hydraulic grain size characteristics, (2) clarify the different types of ‘times’ and suggest a precise and consistent terminology for future use, and (3) compile and discuss factors influencing the times of signal transfer along sediment routing systems and how those times vary with hydraulic grain size characteristics. Unraveling different types of signals and distinctive time periods related to signal propagation addresses the discrepancies mentioned above and allows a more comprehensive exploration of event preservation in stratigraphy – a prerequisite for reliable environmental reconstructions from terrestrially derived sedimentary records.
KW  - signal propagation
KW  - landscape transience
KW  - source-to-sink
KW  - stratigraphy
KW  - response time
Y1  - 2021
U6  - https://doi.org/10.3389/feart.2021.628315
SN  - 2296-6463
VL  - 9
SP  - 1
EP  - 26
PB  - Frontiers Media
CY  - Lausanne, Schweiz
ER  - 
TY  - JOUR
A1  - Zapata, Sebastian
A1  - Sobel, Edward
A1  - Del Papa, Cecilia
A1  - Glodny, Johannes
T1  - Upper Plate Controls on the Formation of Broken Foreland Basins in the Andean Retroarc Between 26°S and 28°S
BT  - From Cretaceous Rifting to Paleogene and Miocene Broken Foreland Basins
JF  - Geochemistry, Geophysics, Geosystems
N2  - Marked along-strike changes in stratigraphy, mountain belt morphology, basement exhumation, and deformation styles characterize the Andean retroarc; these changes have previously been related to spatiotemporal variations in the subduction angle. We modeled new apatite fission track and apatite (U-Th-Sm)/He data from nine ranges located between 26 degrees S and 28 degrees S. Using new and previously published data, we constructed a Cretaceous to Pliocene paleogeographic model that delineates a four-stage tectonic evolution: extensional tectonics during the Cretaceous (120-75 Ma), the formation of a broken foreland basin between 55 and 30 Ma, reheating due to burial beneath sedimentary rocks (18-13 Ma), and deformation, exhumation, and surface uplift during the Late Miocene and the Pliocene (13-3 Ma). Our model highlights how preexisting upper plate structures control the deformation patterns of broken foreland basins. Because retroarc deformation predates flat-slab subduction, we propose that slab anchoring may have been the precursor of Eocene-Oligocene compression in the Andean retroarc. Our model challenges models which consider broken foreland basins and retroarc deformation in the NW Argentinian Andes to be directly related to Miocene flat subduction.
KW  - Northern Sierras Pampeanas
KW  - Fission-track thermochronology
KW  - Middle Eocene deformation
KW  - Santa-Barbara system
KW  - flat-slab subduction
KW  - tectonic inversion
KW  - Apatite (U-TH)/HE
KW  - Puna Plateau
KW  - radiation-damage
KW  - length measurements
Y1  - 2019
VL  - 21
IS  - 7
PB  - John Wiley & Sons, Inc.
CY  - New Jersey
ER  - 
TY  - JOUR
A1  - Lu, Yin
A1  - Dewald, Nico
A1  - Koutsodendris, Andreas
A1  - Kaboth-Bahr, Stefanie
A1  - Rösler, Wolfgang
A1  - Fang, Xiaomin
A1  - Pross, Jörg
A1  - Appel, Erwin
A1  - Friedrich, Oliver
T1  - Sedimentological evidence for pronounced glacial-interglacial climate fluctuations in NE Tibet in the latest Pliocene to early Pleistocene
JF  - Paleoceanography and Paleoclimatology
N2  - The intensification of Northern Hemisphere glaciation (iNHG) and uplift of the Tibetan Plateau have been argued to be among the main drivers of climate change in midlatitude Central Asia during the Pliocene/Pleistocene. While most proxy records that support this hypothesis are from regions outside the Tibetan Plateau (such as from the Chinese Loess Plateau), detailed paleoclimatic information for the plateau itself during that time has yet remained elusive. Here we present a temporally highly resolved (similar to 500 years) sedimentological record from the Qaidam Basin situated on the northeastern Tibetan Plateau that shows pronounced glacial-interglacial climate variability during the interval from 2.7 to 2.1 Ma. Glacial (interglacial) intervals are generally characterized by coarser (finer) grain size, minima (maxima) in organic matter content, and maxima (minima) in carbonate content. Comparison of our results with Earth's orbital parameters and proxy records from the Chinese Loess Plateau suggests that the observed climate fluctuations were mainly driven by changes in the Siberian High/East Asian winter monsoon system as a response to the iNHG. They are further proposed to be enhanced by the topography of the Tibetan Plateau and its impact on the position and intensity of the westerlies.
KW  - Western Qaidam Basin
KW  - grain-size distribution
KW  - lake Donggi Cona
KW  - Chinese loess
KW  - Central-Asia
KW  - transport processes
KW  - Qilian mountains
KW  - dust sources
KW  - plateau
KW  - record
Y1  - 2020
VL  - 35
IS  - 5
PB  - John Wiley & Sons, Inc.
CY  - New Jersey
ER  - 
TY  - JOUR
A1  - Smirnov, Artem G.
A1  - Kronberg, Elena A.
A1  - Daly, Patrick W.
A1  - Aseev, Nikita
A1  - Shprits, Yuri
A1  - Kellerman, Adam C.
T1  - Adiabatic Invariants Calculations for Cluster Mission: A Long-Term Product for Radiation Belts Studies
JF  - Journal of Geophysical Research: Space Physics
N2  - The Cluster mission has produced a large data set of electron flux measurements in the Earth's magnetosphere since its launch in late 2000. Electron fluxes are measured using Research with Adaptive Particle Imaging Detector (RAPID)/Imaging Electron Spectrometer (IES) detector as a function of energy, pitch angle, spacecraft position, and time. However, no adiabatic invariants have been calculated for Cluster so far. In this paper we present a step-by-step guide to calculations of adiabatic invariants and conversion of the electron flux to phase space density (PSD) in these coordinates. The electron flux is measured in two RAPID/IES energy channels providing pitch angle distribution at energies 39.2-50.5 and 68.1-94.5 keV in nominal mode since 2004. A fitting method allows to expand the conversion of the differential fluxes to the range from 40 to 150 keV. Best data coverage for phase space density in adiabatic invariant coordinates can be obtained for values of second adiabatic invariant, K, similar to 10(2), and values of the first adiabatic invariant mu in the range approximate to 5-20 MeV/G. Furthermore, we describe the production of a new data product "LSTAR," equivalent to the third adiabatic invariant, available through the Cluster Science Archive for years 2001-2018 with 1-min resolution. The produced data set adds to the availability of observations in Earth's radiation belts region and can be used for long-term statistical purposes.
KW  - L-Asterisk
KW  - magnetosphere
KW  - electrons
KW  - model
Y1  - 2019
VL  - 125
IS  - 2
PB  - John Wiley & Sons, Inc.
CY  - New Jersey
ER  - 
TY  - JOUR
A1  - Zeeden, Christian
A1  - Obreht, Igor
A1  - Veres, Daniel
A1  - Kaboth-Bahr, Stefanie
A1  - Hošek, Jan
A1  - Marković, Slobodan B.
A1  - Bösken, Janina
A1  - Lehmkuhl, Frank
A1  - Rolf, Christian
A1  - Hambach, Ulrich
T1  - Smoothed millennial-scale palaeoclimatic reference data as unconventional comparison targets: Application to European loess records
JF  - Scientific Reports
N2  - Millennial-scale palaeoclimate variability has been documented in various terrestrial and marine palaeoclimate proxy records throughout the Northern Hemisphere for the last glacial cycle. Its clear expression and rapid shifts between different states of climate (Greenland Interstadials and Stadials) represents a correlation tool beyond the resolution of e.g. luminescence dating, especially relevant for terrestrial deposits. Usually, comparison of terrestrial proxy datasets and the Greenland ice cores indicates a complex expression of millennial-scale climate variability as recorded in terrestrial geoarchives including loess. Loess is the most widespread terrestrial geoarchive of the Quaternary and especially widespread over Eurasia. However, loess often records a smoothed representation of millennial-scale variability without all fidelity when compared to the Greenland data, this being a relevant limiting feature in integrating loess with other palaeoclimate records. To better understand the loess proxy-response to millennial-scale climate variability, we simulate a proxy signal smoothing by natural processes through application of low-pass filters of delta O-18 data from Greenland, a high-resolution palaeoclimate reference record, alongside speleothem isotope records from the Black Sea-Mediterranean region. We show that low-pass filters represent rather simple models for better constraining the expression of millennial-scale climate variability in low sedimentation environments, and in sediments where proxy-response signals are most likely affected by natural smoothing (by e.g. bioturbation). Interestingly, smoothed datasets from Greenland and the Black Sea-Mediterranean region are most similar in the last similar to 15 ka and between similar to 50-30 ka. Between similar to 30-15 ka, roughly corresponding to the Last Glacial Maximum and the deglaciation, the records show dissimilarities, challenging the construction of robust correlative time-scales in this age range. From our analysis it becomes apparent that patterns of palaeoclimate signals in loess-palaeosol sequences often might be better explained by smoothed Greenland reference data than the original high-resolution Greenland dataset, or other reference data. This opens the possibility to better assess the temporal resolution and palaeoclimate potential of loess-palaeosol sequences in recording supra-regional climate patterns, as well as to securely integrate loess with other chronologically better-resolved palaeoclimate records.
KW  - last glacial period
KW  - Western Interior Basin
KW  - high-resolution record
KW  - Greenland ice cores
KW  - paleosol sequence
KW  - time-scale
KW  - Chinese loess
KW  - astronomical calibration
KW  - chronology (AICC2012)
KW  - Antarctic ice
Y1  - 2020
VL  - 10
IS  - 1
PB  - Springer Nature
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Naliboff, John B.
A1  - Glerum, Anne
A1  - Brune, Sascha
A1  - Péron-Pinvidic, G.
A1  - Wrona, Thilo
T1  - Development of 3-D rift heterogeneity through fault network evolution
JF  - Geophysical Research Letters
N2  - Observations of rift and rifted margin architecture suggest that significant spatial and temporal structural heterogeneity develops during the multiphase evolution of continental rifting. Inheritance is often invoked to explain this heterogeneity, such as preexisting anisotropies in rock composition, rheology, and deformation. Here, we use high-resolution 3-D thermal-mechanical numerical models of continental extension to demonstrate that rift-parallel heterogeneity may develop solely through fault network evolution during the transition from distributed to localized deformation. In our models, the initial phase of distributed normal faulting is seeded through randomized initial strength perturbations in an otherwise laterally homogeneous lithosphere extending at a constant rate. Continued extension localizes deformation onto lithosphere-scale faults, which are laterally offset by tens of km and discontinuous along-strike. These results demonstrate that rift- and margin-parallel heterogeneity of large-scale fault patterns may in-part be a natural byproduct of fault network coalescence.
KW  - magma-poor
KW  - continental lithosphere
KW  - extension
KW  - insights
KW  - margins
KW  - architecture
KW  - systems
KW  - models
KW  - sea
KW  - reactivation
Y1  - 2019
VL  - 47
IS  - 13
PB  - John Wiley & Sons, Inc.
CY  - New Jersey
ER  - 
TY  - JOUR
A1  - Coesfeld, Jacqueline
A1  - Kuester, Theres
A1  - Kuechly, Helga U.
A1  - Kyba, Christopher C. M.
T1  - Reducing variability and removing natural light from nighttime satellite imagery: A case study using the VIIRS DNB
JF  - Sensors
N2  - Temporal variation of natural light sources such as airglow limits the ability of night light sensors to detect changes in small sources of artificial light (such as villages). This study presents a method for correcting for this effect globally, using the satellite radiance detected from regions without artificial light emissions. We developed a routine to define an approximate grid of locations worldwide that do not have regular light emission. We apply this method with a 5 degree equally spaced global grid (total of 2016 individual locations), using data from the Visible Infrared Imaging Radiometer Suite (VIIRS) Day-Night Band (DNB). This code could easily be adapted for other future global sensors. The correction reduces the standard deviation of data in the Earth Observation Group monthly DNB composites by almost a factor of two. The code and datasets presented here are available under an open license by GFZ Data Services, and are implemented in the Radiance Light Trends web application.
KW  - airglow
KW  - artificial light
KW  - calibration
KW  - VIIRS DNB
KW  - nightlights
KW  - remote sensing
Y1  - 2020
VL  - 20
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Rolfes, Manfred
A1  - Wilhelm, Jan Lorenz
T1  - Urban complexity and urban change
BT  - Co-irritation, co-evolution and co-design with the Potsdam lodestar approach
JF  - Urban Change and Citizenship in Times of Crisis
N2  - The chapter illustrates how cities can be understood from a system–theory perspective as complex social systems. It argues that the classical and linear intervention methods are often no (longer) suitable for the complex structure, temporal dynamics and multifaceted processuality of urban development. It offers a systemic and systems theory-inspired method as an alternative approach, which allows for extended possibilities that are more appropriate for dealing with urban development processes. The method was developed on the basis of practical experience and theoretical insights. The approach should demonstrate for local decision-makers potential areas of activity for organising urban changes through co-design.
Y1  - 2020
SN  - 978-0-429-26226-5
SN  - 978-0-367-20562-1
SP  - 135
EP  - 155
PB  - Routledge
CY  - London
ER  - 
TY  - JOUR
A1  - Engels, Stefan
A1  - Medeiros, Andrew S.
A1  - Axford, Yarrow
A1  - Brooks, Steve
A1  - Heiri, Oliver
A1  - Luoto, Tomi P.
A1  - Nazarova, Larisa B.
A1  - Porinchu, David F.
A1  - Quinlan, Roberto
A1  - Self, Angela E.
T1  - Temperature change as a driver of spatial patterns and long-term trends in chironomid (Insecta: Diptera) diversity
JF  - Global change biology
N2  - Anthropogenic activities have led to a global decline in biodiversity, and monitoring studies indicate that both insect communities and wetland ecosystems are particularly affected. However, there is a need for long-term data (over centennial or millennial timescales) to better understand natural community dynamics and the processes that govern the observed trends. Chironomids (Insecta: Diptera: Chironomidae) are often the most abundant insects in lake ecosystems, sensitive to environmental change, and, because their larval exoskeleton head capsules preserve well in lake sediments, they provide a unique record of insect community dynamics through time. Here, we provide the results of a metadata analysis of chironomid diversity across a range of spatial and temporal scales. First, we analyse spatial trends in chironomid diversity using Northern Hemispheric data sets overall consisting of 837 lakes. Our results indicate that in most of our data sets, summer temperature (T-jul) is strongly associated with spatial trends in modern-day chironomid diversity. We observe a strong increase in chironomid alpha diversity with increasing T-jul in regions with present-day T-jul between 2.5 and 14 degrees C. In some areas with T-jul > 14 degrees C, chironomid diversity stabilizes or declines. Second, we demonstrate that the direction and amplitude of change in alpha diversity in a compilation of subfossil chironomid records spanning the last glacial-interglacial transition (similar to 15,000-11,000 years ago) are similar to those observed in our modern data. A compilation of Holocene records shows that during phases when the amplitude of temperature change was small, site-specific factors had a greater influence on the chironomid fauna obscuring the chironomid diversity-temperature relationship. Our results imply expected overall chironomid diversity increases in colder regions such as the Arctic under sustained global warming, but with complex and not necessarily predictable responses for individual sites.
KW  - Arctic
KW  - biodiversity
KW  - climate warming
KW  - freshwater ecosystems
KW  - insects
KW  - palaeoecology
KW  - Quaternary
Y1  - 2019
U6  - https://doi.org/10.1111/gcb.14862
SN  - 1354-1013
SN  - 1365-2486
VL  - 26
IS  - 3
SP  - 1155
EP  - 1169
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Repasch, Marisa
A1  - Wittmann, Hella
A1  - Scheingross, Joel S.
A1  - Sachse, Dirk
A1  - Szupiany, Ricardo
A1  - Orfeo, Oscar
A1  - Fuchs, Margret
A1  - Hovius, Niels
T1  - Sediment Transit Time and Floodplain Storage Dynamics in Alluvial Rivers Revealed by Meteoric 10Be
JF  - Journal of Geophysical Research: Earth Surface
N2  - Quantifying the time scales of sediment transport and storage through river systems is fundamental for understanding weathering processes, biogeochemical cycling, and improving watershed management, but measuring sediment transit time is challenging. Here we provide the first systematic test of measuring cosmogenic meteoric Beryllium-10 (10Bem) in the sediment load of a large alluvial river to quantify sediment transit times. We take advantage of a natural experiment in the Rio Bermejo, a lowland alluvial river traversing the east Andean foreland basin in northern Argentina. This river has no tributaries along its trunk channel for nearly 1,300 km downstream from the mountain front. We sampled suspended sediment depth profiles along the channel and measured the concentrations of 10Bem in the chemically extracted grain coatings. We calculated depth-integrated 10Bem concentrations using sediment flux data and found that 10Bem concentrations increase 230% from upstream to downstream, indicating a mean total sediment transit time of 8.4 ± 2.2 kyr. Bulk sediment budget-based estimates of channel belt and fan storage times suggest that the 10Bem tracer records mixing of old and young sediment reservoirs. On a reach scale, 10Bem transit times are shorter where the channel is braided and superelevated above the floodplain, and longer where the channel is incised and meandering, suggesting that transit time is controlled by channel morphodynamics. This is the first systematic application of 10Bem as a sediment transit time tracer and highlights the method's potential for inferring sediment routing and storage dynamics in large river systems.
KW  - meteoric 10Be
KW  - sediment transit time
KW  - river sediment
KW  - floodplains
KW  - sediment routing
Y1  - 2019
U6  - https://doi.org/10.1029/2019JF005419
SN  - 2169-9011
SN  - 2169-9003
VL  - 125
PB  - Wiley
CY  - Hoboken, NJ
ER  - 
TY  - JOUR
A1  - Smith, Taylor
A1  - Bookhagen, Bodo
T1  - Assessing Multi-Temporal Snow-Volume Trends in High Mountain Asia From 1987 to 2016 Using High-Resolution Passive Microwave Data
JF  - Frontiers in Earth Science
N2  - High Mountain Asia (HMA) is dependent upon both the amount and timing of snow and glacier meltwater. Previous model studies and coarse resolution (0.25° × 0.25°, ∼25 km × 25 km) passive microwave assessments of trends in the volume and timing of snowfall, snowmelt, and glacier melt in HMA have identified key spatial and seasonal heterogeneities in the response of snow to changes in regional climate. Here we use recently developed, continuous, internally consistent, and high-resolution passive microwave data (3.125 km × 3.125 km, 1987–2016) from the special sensor microwave imager instrument family to refine and extend previous estimates of changes in the snow regime of HMA. We find an overall decline in snow volume across HMA; however, there exist spatially contiguous regions of increasing snow volume—particularly during the winter season in the Pamir, Karakoram, Hindu Kush, and Kunlun Shan. Detailed analysis of changes in snow-volume trends through time reveal a large step change from negative trends during the period 1987–1997, to much more positive trends across large regions of HMA during the periods 1997–2007 and 2007–2016. We also find that changes in high percentile monthly snow-water volume exhibit steeper trends than changes in low percentile snow-water volume, which suggests a reduction in the frequency of high snow-water volumes in much of HMA. Regions with positive snow-water storage trends generally correspond to regions of positive glacier mass balances.
KW  - snow
KW  - glacier
KW  - climate change
KW  - passive microwave
KW  - special sensor microwave imager
KW  - special sensor microwave imager/sounder
Y1  - 2020
U6  - https://doi.org/10.3389/feart.2020.559175
SN  - 2296-6463
VL  - 8
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Runge, Alexandra
A1  - Grosse, Guido
T1  - Mosaicking Landsat and Sentinel-2 Data to Enhance LandTrendr Time Series Analysis in Northern High Latitude Permafrost Regions
JF  - Remote Sensing
N2  - Permafrost is warming in the northern high latitudes, inducing highly dynamic thaw-related permafrost disturbances across the terrestrial Arctic. Monitoring and tracking of permafrost disturbances is important as they impact surrounding landscapes, ecosystems and infrastructure. Remote sensing provides the means to detect, map, and quantify these changes homogeneously across large regions and time scales. Existing Landsat-based algorithms assess different types of disturbances with similar spatiotemporal requirements. However, Landsat-based analyses are restricted in northern high latitudes due to the long repeat interval and frequent clouds, in particular at Arctic coastal sites. We therefore propose to combine Landsat and Sentinel-2 data for enhanced data coverage and present a combined annual mosaic workflow, expanding currently available algorithms, such as LandTrendr, to achieve more reliable time series analysis. We exemplary test the workflow for twelve sites across the northern high latitudes in Siberia. We assessed the number of images and cloud-free pixels, the spatial mosaic coverage and the mosaic quality with spectral comparisons. The number of available images increased steadily from 1999 to 2019 but especially from 2016 onward with the addition of Sentinel-2 images. Consequently, we have an increased number of cloud-free pixels even under challenging environmental conditions, which then serve as the input to the mosaicking process. In a comparison of annual mosaics, the Landsat+Sentinel-2 mosaics always fully covered the study areas (99.9–100 %), while Landsat-only mosaics contained data-gaps in the same years, only reaching coverage percentages of 27.2 %, 58.1 %, and 69.7 % for Sobo Sise, East Taymyr, and Kurungnakh in 2017, respectively. The spectral comparison of Landsat image, Sentinel-2 image, and Landsat+Sentinel-2 mosaic showed high correlation between the input images and mosaic bands (e.g., for Kurungnakh 0.91–0.97 between Landsat and Landsat+Sentinel-2 mosaic and 0.92–0.98 between Sentinel-2 and Landsat+Sentinel-2 mosaic) across all twelve study sites, testifying good quality mosaic results. Our results show that especially the results for northern, coastal areas was substantially improved with the Landsat+Sentinel-2 mosaics. By combining Landsat and Sentinel-2 data we accomplished to create reliably high spatial resolution input mosaics for time series analyses. Our approach allows to apply a high temporal continuous time series analysis to northern high latitude permafrost regions for the first time, overcoming substantial data gaps, and assess permafrost disturbance dynamics on an annual scale across large regions with algorithms such as LandTrendr by deriving the location, timing and progression of permafrost thaw disturbances
KW  - time series analysis
KW  - data fusion
KW  - disturbance tracking
KW  - permafrost
KW  - permafrost thaw
Y1  - 2020
U6  - https://doi.org/10.3390/rs12152471
SN  - 2072-4292
VL  - 12
IS  - 15
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Arnous, Ahmad
A1  - Zeckra, Martin
A1  - Venerdini, Agostina
A1  - Alvarado, Patricia
A1  - Arrowsmith, Ramón
A1  - Guillemoteau, Julien
A1  - Landgraf, Angela
A1  - Gutiérrez, Adolfo Antonio
A1  - Strecker, Manfred
T1  - Neotectonic Activity in the Low-Strain Broken Foreland (Santa Bárbara System) of the North-Western Argentinean Andes (26°S)
JF  - Lithosphere
N2  - Uplift in the broken Andean foreland of the Argentine Santa Bárbara System (SBS) is associated with the contractional reactivation of basement anisotropies, similar to those reported from the thick-skinned Cretaceous-Eocene Laramide province of North America. Fault scarps, deformed Quaternary deposits and landforms, disrupted drainage patterns, and medium-sized earthquakes within the SBS suggest that movement along these structures may be a recurring phenomenon, with yet to be defined repeat intervals and rupture lengths. In contrast to the Subandes thrust belt farther north, where eastward-migrating deformation has generated a well-defined thrust front, the SBS records spatiotemporally disparate deformation along structures that are only known to the first order. We present herein the results of geomorphic desktop analyses, structural field observations, and 2D electrical resistivity tomography and seismic-refraction tomography surveys and an interpretation of seismic reflection profiles across suspected fault scarps in the sedimentary basins adjacent to the Candelaria Range (CR) basement uplift, in the south-central part of the SBS. Our analysis in the CR piedmont areas reveals consistency between the results of near-surface electrical resistivity and seismic-refraction tomography surveys, the locations of prominent fault scarps, and structural geometries at greater depth imaged by seismic reflection data. We suggest that this deformation is driven by deep-seated blind thrusting beneath the CR and associated regional warping, while shortening involving Mesozoic and Cenozoic sedimentary strata in the adjacent basins was accommodated by layer-parallel folding and flexural-slip faults that cut through Quaternary landforms and deposits at the surface.
Y1  - 2019
U6  - https://doi.org/10.2113/2020/8888588
SN  - 1947-4253
SN  - 1941-8264
VL  - 2020
IS  - 1
SP  - 1
EP  - 25
PB  - GSA
CY  - Boulder, Colo.
ER  - 
TY  - JOUR
A1  - Milewski, Robert
A1  - Chabrillat, Sabine
A1  - Bookhagen, Bodo
T1  - Analyses of Namibian Seasonal Salt Pan Crust Dynamics and Climatic Drivers Using Landsat 8 Time-Series and Ground Data
JF  - Remote Sensing
N2  - Salt pans are highly dynamic environments that are difficult to study by in situ methods because of their harsh climatic conditions and large spatial areas. Remote sensing can help to elucidate their environmental dynamics and provide important constraints regarding their sedimentological, mineralogical, and hydrological evolution. This study utilizes spaceborne multitemporal multispectral optical data combined with spectral endmembers to document spatial distribution of surface crust types over time on the Omongwa pan located in the Namibian Kalahari. For this purpose, 49 surface samples were collected for spectral and mineralogical characterization during three field campaigns (2014–2016) reflecting different seasons and surface conditions of the salt pan. An approach was developed to allow the spatiotemporal analysis of the salt pan crust dynamics in a dense time-series consisting of 77 Landsat 8 cloud-free scenes between 2014 and 2017, covering at least three major wet–dry cycles. The established spectral analysis technique Sequential Maximum Angle Convex Cone (SMACC) extraction method was used to derive image endmembers from the Landsat time-series stack. Evaluation of the extracted endmember set revealed that the multispectral data allowed the differentiation of four endmembers associated with mineralogical mixtures of the crust’s composition in dry conditions and three endmembers associated with flooded or muddy pan conditions. The dry crust endmember spectra have been identified in relation to visible, near infrared, and short-wave infrared (VNIR–SWIR) spectroscopy and X-ray diffraction (XRD) analyses of the collected surface samples. According these results, the spectral endmembers are interpreted as efflorescent halite crust, mixed halite–gypsum crust, mixed calcite quartz sepiolite crust, and gypsum crust. For each Landsat scene the spatial distribution of these crust types was mapped with the Spectral Angle Mapper (SAM) method and significant spatiotemporal dynamics of the major surface crust types were observed. Further, the surface crust dynamics were analyzed in comparison with the pan’s moisture regime and other climatic parameters. The results show that the crust dynamics are mainly driven by flooding events in the wet season, but are also influenced by temperature and aeolian activity in the dry season. The approach utilized in this study combines the advantages of multitemporal satellite data for temporal event characterization with advantages from hyperspectral methods for the image and ground data analyses that allow improved mineralogical differentiation and characterization.
KW  - salt pan
KW  - playa
KW  - spectral analysis
KW  - crust
KW  - saline pan cycle
KW  - evaporites
KW  - time-series mapping
Y1  - 2019
U6  - https://doi.org/10.3390/rs12030474
SN  - 2072-4292
IS  - 3
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Nardini, Livia
A1  - Rybacki, Erik
A1  - Krause, Michael
A1  - Morales, Luiz F.G.
A1  - Dresen, Georg
T1  - Control of the geometric arrangement of material heterogeneities on strain localization at the brittle-to-ductile transition in experimentally deformed carbonate rocks
JF  - Journal of Structural Geology
N2  - Triaxial high temperature (900 °C) deformation experiments were conducted at constant strain rate in a Paterson-type deformation apparatus on cylinders of Carrara marble with two right or left stepping, non-overlapping weak inclusions of Solnhofen limestone, oriented at 45° to the cylinders’ longitudinal axes. Applying different values of confinement (30, 50, 100 and 300 MPa) we induced various amounts of brittle deformation in the marble matrix and investigated the effect of brittle precursors on the initiation and development of heterogeneity-induced high temperature shear zones.

Viscosity contrast between the matrix and the inclusions induces local stress concentration at the tips of these latter. The initial arrangement of the inclusions results in either an overpressured (contractional) or underpressured (extensional) domain in the step-over region of the sample. At low confinement (30 and 50 MPa) abundant brittle deformation is observed, but the spatial distribution of microfractures is dependent on the kinematics of the step-over region: microcracks occur either along the shearing plane between inclusions (in extensional bridge samples), or broadly distributed outside the step-over region (contractional bridge samples). Accordingly, ductile deformation localizes along the inclusions plane in the extensional bridge samples as opposed to distributing over large areas of the matrix in the contractional bridge samples. If microcracking is suppressed (high confinement), strain is accommodated by viscous creep and strain progressively de-localizes in extensional bridge samples. Our experiments demonstrate that brittle precursors enhance the degree of localization in the ductile deformation regime, but only if the interaction of pre-existing heterogeneities induces an extensional mean stress regime in between.
KW  - High-temperature shear zones
KW  - Triaxial deformation
KW  - Brittle precursors
KW  - Strain localization Carrara marble
Y1  - 2019
U6  - https://doi.org/10.1016/j.jsg.2020.104038
SN  - 0191-8141
VL  - 135
PB  - Pergamon Press
CY  - Oxford ; Frankfurt, M.
ER  - 
TY  - JOUR
A1  - Dommain, René
A1  - Andama, Morgan
A1  - McDonough, Molly M.
A1  - Prado, Natalia A.
A1  - Goldhammer, Tobias
A1  - Potts, Richard
A1  - Maldonado, Jesús E.
A1  - Nkurunungi, John Bosco
A1  - Campana, Michael G.
T1  - The Challenges of Reconstructing Tropical Biodiversity With Sedimentary Ancient DNA
BT  - A 2200-Year-Long Metagenomic Record From Bwindi Impenetrable Forest, Uganda
JF  - Frontiers in Ecology and Evolution
N2  - Sedimentary ancient DNA has been proposed as a key methodology for reconstructing biodiversity over time. Yet, despite the concentration of Earth’s biodiversity in the tropics, this method has rarely been applied in this region. Moreover, the taphonomy of sedimentary DNA, especially in tropical environments, is poorly understood. This study elucidates challenges and opportunities of sedimentary ancient DNA approaches for reconstructing tropical biodiversity. We present shotgun-sequenced metagenomic profiles and DNA degradation patterns from multiple sediment cores from Mubwindi Swamp, located in Bwindi Impenetrable Forest (Uganda), one of the most diverse forests in Africa. We describe the taxonomic composition of the sediments covering the past 2200 years and compare the sedimentary DNA data with a comprehensive set of environmental and sedimentological parameters to unravel the conditions of DNA degradation. Consistent with the preservation of authentic ancient DNA in tropical swamp sediments, DNA concentration and mean fragment length declined exponentially with age and depth, while terminal deamination increased with age. DNA preservation patterns cannot be explained by any environmental parameter alone, but age seems to be the primary driver of DNA degradation in the swamp. Besides degradation, the presence of living microbial communities in the sediment also affects DNA quantity. Critically, 92.3% of our metagenomic data of a total 81.8 million unique, merged reads cannot be taxonomically identified due to the absence of genomic references in public databases. Of the remaining 7.7%, most of the data (93.0%) derive from Bacteria and Archaea, whereas only 0–5.8% are from Metazoa and 0–6.9% from Viridiplantae, in part due to unbalanced taxa representation in the reference data. The plant DNA record at ordinal level agrees well with local pollen data but resolves less diversity. Our animal DNA record reveals the presence of 41 native taxa (16 orders) including Afrotheria, Carnivora, and Ruminantia at Bwindi during the past 2200 years. Overall, we observe no decline in taxonomic richness with increasing age suggesting that several-thousand-year-old information on past biodiversity can be retrieved from tropical sediments. However, comprehensive genomic surveys of tropical biota need prioritization for sedimentary DNA to be a viable methodology for future tropical biodiversity studies.
KW  - sedimentary ancient DNA
KW  - tropical biodiversity
KW  - DNA preservation
KW  - sediment
KW  - tropical swamp
KW  - shotgun sequencing
KW  - metagenomic analysis
Y1  - 2019
U6  - https://doi.org/10.3389/fevo.2020.00218
SN  - 2296-701X
VL  - 8
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Ayzel, Georgy
A1  - Scheffer, Tobias
A1  - Heistermann, Maik
T1  - RainNet v1.0
BT  - a convolutional neural network for radar-based precipitation nowcasting
JF  - Geoscientific Model Development
N2  - In this study, we present RainNet, a deep convolutional neural network for radar-based precipitation nowcasting. Its design was inspired by the U-Net and SegNet families of deep learning models, which were originally designed for binary segmentation tasks. RainNet was trained to predict continuous precipitation intensities at a lead time of 5min, using several years of quality-controlled weather radar composites provided by the German Weather Service (DWD). That data set covers Germany with a spatial domain of 900km × 900km and has a resolution of 1km in space and 5min in time. Independent verification experiments were carried out on 11 summer precipitation events from 2016 to 2017. In order to achieve a lead time of 1h, a recursive approach was implemented by using RainNet predictions at 5min lead times as model inputs for longer lead times. In the verification experiments, trivial Eulerian persistence and a conventional model based on optical flow served as benchmarks. The latter is available in the rainymotion library and had previously been shown to outperform DWD's operational nowcasting model for the same set of verification events.

RainNet significantly outperforms the benchmark models at all lead times up to 60min for the routine verification metrics mean absolute error (MAE) and the critical success index (CSI) at intensity thresholds of 0.125, 1, and 5mm h⁻¹. However, rainymotion turned out to be superior in predicting the exceedance of higher intensity thresholds (here 10 and 15mm h⁻¹). The limited ability of RainNet to predict heavy rainfall intensities is an undesirable property which we attribute to a high level of spatial smoothing introduced by the model. At a lead time of 5min, an analysis of power spectral density confirmed a significant loss of spectral power at length scales of 16km and below. Obviously, RainNet had learned an optimal level of smoothing to produce a nowcast at 5min lead time. In that sense, the loss of spectral power at small scales is informative, too, as it reflects the limits of predictability as a function of spatial scale. Beyond the lead time of 5min, however, the increasing level of smoothing is a mere artifact – an analogue to numerical diffusion – that is not a property of RainNet itself but of its recursive application. In the context of early warning, the smoothing is particularly unfavorable since pronounced features of intense precipitation tend to get lost over longer lead times. Hence, we propose several options to address this issue in prospective research, including an adjustment of the loss function for model training, model training for longer lead times, and the prediction of threshold exceedance in terms of a binary segmentation task. Furthermore, we suggest additional input data that could help to better identify situations with imminent precipitation dynamics. The model code, pretrained weights, and training data are provided in open repositories as an input for such future studies.
KW  - weather
KW  - models
KW  - skill
Y1  - 2020
U6  - https://doi.org/10.5194/gmd-13-2631-2020
SN  - 1991-959X
SN  - 1991-9603
VL  - 13
IS  - 6
SP  - 2631
EP  - 2644
PB  - Copernicus Publ.
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Marwan, Norbert
A1  - Maheswaran, Rathinasamy
A1  - Öztürk, Ugur
A1  - Kurths, Jürgen
A1  - Merz, Bruno
T1  - Optimal design of hydrometric station networks based on complex network analysis
JF  - Hydrology and Earth System Sciences
N2  - Hydrometric networks play a vital role in providing information for decision-making in water resource management. They should be set up optimally to provide as much information as possible that is as accurate as possible and, at the same time, be cost-effective. Although the design of hydrometric networks is a well-identified problem in hydrometeorology and has received considerable attention, there is still scope for further advancement. In this study, we use complex network analysis, defined as a collection of nodes interconnected by links, to propose a new measure that identifies critical nodes of station networks. The approach can support the design and redesign of hydrometric station networks. The science of complex networks is a relatively young field and has gained significant momentum over the last few years in different areas such as brain networks, social networks, technological networks, or climate networks. The identification of influential nodes in complex networks is an important field of research. We propose a new node-ranking measure – the weighted degree–betweenness (WDB) measure – to evaluate the importance of nodes in a network. It is compared to previously proposed measures used on synthetic sample networks and then applied to a real-world rain gauge network comprising 1229 stations across Germany to demonstrate its applicability. The proposed measure is evaluated using the decline rate of the network efficiency and the kriging error. The results suggest that WDB effectively quantifies the importance of rain gauges, although the benefits of the method need to be investigated in more detail.
KW  - identifying influential nodes
KW  - climate networks
KW  - rainfall
KW  - streamflow
KW  - synchronization
KW  - precipitation
KW  - classification
KW  - events
Y1  - 2020
U6  - https://doi.org/10.5194/hess-24-2235-2020
SN  - 1027-5606
SN  - 1607-7938
VL  - 24
IS  - 5
SP  - 2235
EP  - 2251
PB  - Copernicus Publ.
CY  - Göttingen
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
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.
KW  - Weather
KW  - Band
KW  - Reflectivity
KW  - Algorithm
KW  - Uncertainties
KW  - Methodology
KW  - Kwajalein
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 Publications
CY  - Göttingen
ER  -