TY  - JOUR
A1  - Lontsi, Agostiny Marrios
A1  - Garcia-Jerez, Antonio
A1  - Camilo Molina-Villegas, Juan
A1  - Jose Sanchez-Sesma, Francisco
A1  - Molkenthin, Christian
A1  - Ohrnberger, Matthias
A1  - Krüger, Frank
A1  - Wang, Rongjiang
A1  - Fah, Donat
T1  - A generalized theory for full microtremor horizontal-to-vertical [H/V(z,f)] spectral ratio interpretation in offshore and onshore environments
JF  - Geophysical journal international
N2  - Advances in the field of seismic interferometry have provided a basic theoretical interpretation to the full spectrum of the microtremor horizontal-to-vertical spectral ratio [H/V(f)]. The interpretation has been applied to ambient seismic noise data recorded both at the surface and at depth. The new algorithm, based on the diffuse wavefield assumption, has been used in inversion schemes to estimate seismic wave velocity profiles that are useful input information for engineering and exploration seismology both for earthquake hazard estimation and to characterize surficial sediments. However, until now, the developed algorithms are only suitable for on land environments with no offshore consideration. Here, the microtremor H/V(z, f) modelling is extended for applications to marine sedimentary environments for a 1-D layered medium. The layer propagator matrix formulation is used for the computation of the required Green’s functions. Therefore, in the presence of a water layer on top, the propagator matrix for the uppermost layer is defined to account for the properties of the water column. As an application example we analyse eight simple canonical layered earth models. Frequencies ranging from 0.2 to 50 Hz are considered as they cover a broad wavelength interval and aid in practice to investigate subsurface structures in the depth range from a few meters to a few hundreds of meters. Results show a marginal variation of 8 per cent at most for the fundamental frequency when a water layer is present. The water layer leads to variations in H/V peak amplitude of up to 50 per cent atop the solid layers.
KW  - Numerical modelling
KW  - Earthquake hazards
KW  - Seismic interferometry
KW  - Site effects
KW  - Theoretical seismology
KW  - Wave propagation
Y1  - 2019
U6  - https://doi.org/10.1093/gji/ggz223
SN  - 0956-540X
SN  - 1365-246X
VL  - 218
IS  - 2
SP  - 1276
EP  - 1297
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Baroni, Gabriele
A1  - Tarantola, S.
T1  - A general probabilistic framework for uncertainty and global sensitivity analysis of deterministic models: A hydrological case study
JF  - Environmental modelling & software with environment data news
N2  - The present study proposes a General Probabilistic Framework (GPF) for uncertainty and global sensitivity analysis of deterministic models in which, in addition to scalar inputs, non-scalar and correlated inputs can be considered as well. The analysis is conducted with the variance-based approach of Sobol/Saltelli where first and total sensitivity indices are estimated. The results of the framework can be used in a loop for model improvement, parameter estimation or model simplification. The framework is applied to SWAP, a 113 hydrological model for the transport of water, solutes and heat in unsaturated and saturated soils. The sources of uncertainty are grouped in five main classes: model structure (soil discretization), input (weather data), time-varying (crop) parameters, scalar parameters (soil properties) and observations (measured soil moisture). For each source of uncertainty, different realizations are created based on direct monitoring activities. Uncertainty of evapotranspiration, soil moisture in the root zone and bottom fluxes below the root zone are considered in the analysis. The results show that the sources of uncertainty are different for each output considered and it is necessary to consider multiple output variables for a proper assessment of the model. Improvements on the performance of the model can be achieved reducing the uncertainty in the observations, in the soil parameters and in the weather data. Overall, the study shows the capability of the GPF to quantify the relative contribution of the different sources of uncertainty and to identify the priorities required to improve the performance of the model. The proposed framework can be extended to a wide variety of modelling applications, also when direct measurements of model output are not available.
KW  - Global sensitivity analysis
KW  - Non-scalar input factors
KW  - Hydrological model
KW  - Multi-variables
Y1  - 2014
U6  - https://doi.org/10.1016/j.envsoft.2013.09.022
SN  - 1364-8152
SN  - 1873-6726
VL  - 51
SP  - 26
EP  - 34
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Herzschuh, Ulrike
A1  - Winter, Katja
A1  - Wünnemann, Bernd
A1  - Li, Shijie
T1  - A general cooling trend on the central Tibetan Plateau throughout the Holocene recorded by the Lake Zigetang pollen spectra
JF  - Quaternary international : the journal of the International Union for Quaternary Research
N2  - A 741-cm-long laminated sediment core, covering the last 10,800 years was collected from Lake Zigetang, central Tibetan Plateau (90.9 degrees E, 32.0 degrees N, 4560m a.s.l.), and analysed palynologically at 69 horizons. Biome reconstruction suggests a dominance of temperate steppe vegetation (mainly Artemisia and Poaceae) on the central Tibetan Plateau during the first half of the Holocene (10.8-4.4 cal. ka BP), while alpine steppes with desert elements (mainly Cyperaceae, Poaceae, Chenopodiaceae, and characteristic high-alpine herb families) tend to dominate the second half (4.4-0 cal. ka BP). The Artemisia/Cyperaceae ratio-a semi-quantitative measure for summer temperature-indicates a general cooling trend throughout the Holocene. Dense temperate steppe vegetation and maximum desert plant withdrawal, however, indicate that a suitable balance of wet and warm conditions for optimum vegetation growth likely occurred during the middle Holocene (7.3-4.4 cal. ka BP). Severe Early Holocene cold events have been reconstructed for 8.7-8.3 and similar to 7.4 cal. ka BP. (c) 2006 Elsevier Ltd and INQUA. All rights reserved.
Y1  - 2006
U6  - https://doi.org/10.1016/j.quaint.2006.02.005
SN  - 1040-6182
VL  - 154
SP  - 113
EP  - 121
PB  - Pergamon Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Maerker, Michael
A1  - Pelacani, Samanta
A1  - Schroeder, Boris
T1  - A functional entity approach to predict soil erosion processes in a small Plio-Pleistocene Mediterranean catchment in Northern Chianti, Italy
JF  - Geomorphology : an international journal on pure and applied geomorphology
N2  - In this paper we evaluate different methods to predict soil erosion processes. We derived different layers of predictor variables for the study area in the Northern Chianti, Italy, describing the soil-lithologic complex, land use, and topographic characteristics. For a subcatchment of the Orme River, we mapped erosion processes by interpreting aerial photographs and field observations. These were classified as erosional response units (ERU), i.e. spatial areas of homogeneous erosion processes. The ERU were used as the response variable in the soil erosion modelling process. We applied two models i) bootstrap aggregation (Random Forest: RF), and ii) stochastic gradient boosting (TreeNet: TN) to predict the potential spatial distribution of erosion processes for the entire Orme River catchment. The models are statistically evaluated using training data and a set of performance parameters such as the area under the receiver operating characteristic curve (AUC), Cohen's Kappa, and pseudo R2. Variable importance and response curves provide further insight into controlling factors of erosion. Both models provided good performance in terms of classification and calibration; however, TN outperformed RF. Similar classes such as active and inactive landslides can be discriminated and well interpreted by considering response curves and relative variable importance. The spatial distribution of the predicted erosion susceptibilities generally follows topographic constraints and is similar for both models. Hence, the model-based delineation of ERU on the basis of soil and terrain information is a valuable tool in geomorphology; it provides insights into factors controlling erosion processes and may allow the extrapolation and prediction of erosion processes in unsurveyed areas.
KW  - Erosion processes
KW  - Boostrap aggregation
KW  - Stochastic gradient boosting
KW  - Spatially explicit prediction
KW  - Tuscany
KW  - Italy
Y1  - 2011
U6  - https://doi.org/10.1016/j.geomorph.2010.10.022
SN  - 0169-555X
VL  - 125
IS  - 4
SP  - 530
EP  - 540
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Busch, Jan Philip
A1  - Meißner, Tobias
A1  - Potthoff, Annegret
A1  - Bleyl, Steffen
A1  - Georgi, Anett
A1  - Mackenzie, Katrin
A1  - Trabitzsch, Ralf
A1  - Werban, Ulrike
A1  - Oswald, Sascha
T1  - A field investigation on transport of carbon-supported nanoscale zero-valent iron (nZVI) in groundwater
JF  - Journal of contaminant hydrology
N2  - The application of nanoscale zero-valent iron (nZVI) for subsurface remediation of groundwater contaminants is a promising new technology, which can be understood as alternative to the permeable reactive barrier technique using granular iron. Dechlorination of organic contaminants by zero-valent iron seems promising. Currently, one limitation to widespread deployment is the fast agglomeration and sedimentation of nZVI in colloidal suspensions, even more so when in soils and sediments, which limits the applicability for the treatment of sources and plumes of contamination. Colloid-supported nZVI shows promising characteristics to overcome these limitations. Mobility of Carbo-Iron Colloids (CIC) - a newly developed composite material based on finely ground activated carbon as a carrier for nZVI - was tested in a field application: In this study, a horizontal dipole flow field was established between two wells separated by 53 m in a confined, natural aquifer. The injection/extraction rate was 500 L/h. Approximately 12 kg of CIC was suspended with the polyanionic stabilizer carboxymethyl cellulose. The suspension was introduced into the aquifer at the injection well. Breakthrough of CIC was observed visually and based on total particle and iron concentrations detected in samples from the extraction well. Filtration of water samples revealed a particle breakthrough of about 12% of the amount introduced. This demonstrates high mobility of CIC particles and we suggest that nZVI carried on CIC can be used for contaminant plume remediation by in-situ formation of reactive barriers. (C) 2015 Elsevier B.V. All rights reserved.
KW  - Nanoscale zero-valent iron (nZVI)
KW  - Fe-C composite
KW  - Carbon colloid
KW  - Field aquifer
KW  - Remediation
KW  - Particle mobility
Y1  - 2015
U6  - https://doi.org/10.1016/j.jconhyd.2015.03.009
SN  - 0169-7722
SN  - 1873-6009
VL  - 181
SP  - 59
EP  - 68
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - THES
A1  - Muksin, Umar
T1  - A fault-controlled geothermal system in Tarutung (North Sumatra, Indonesia)investigated by seismological analysis
N2  - The seismic structure (Vp, Vp/Vs, and Qp anomalies) contributes to the physical properties and the lithology of rocks and possible fluid distribution in the region. The Vp model images the geometry of the Tarutung and the Sarulla basins. Both basins have a depth of around 2.0 km. High Vp/Vs and high attenuation (low Qp) anomalies are observed along the Sarulla graben associated with a weak zone caused by volcanic activities along the graben. Low Vp/Vs and low conductivity anomalies are found in the west of the Tarutung basin. This anomaly is interpreted as dry, compact, and rigid granitic rock in the region as also found by geological observations. Low Vp, high Vp/Vs and low Qp anomalies are found at the east of the Tarutung basin which appear to be associated with the three big geothermal manifestations in Sipoholon, Hutabarat, and Panabungan area. These anomalies are connected with high Vp/Vs and low Qp anomalies below the Tarutung basin at depth of around 3 - 10 km. This suggests that these geothermal manifestations are fed by the same source of the hot fluid below the Tarutung basin. The hot fluids from below the Tarutung basin propagate to the more dilatational and more permeable zone in the northeast. Granite found in the west of the Tarutung basin could also be abundant underneath the basin at a certain depth so that it prevents the hot fluid to be transported directly to the Tarutung basin. High seismic attenuation and low Vp/Vs anomalies are found in the southwest of the Tarutung basin below the Martimbang volcano. These anomalies are associated with hot rock below the volcano without or with less amount of partial melting. There is no indication that the volcano controls the geothermal system around the Tarutung basin. The geothermal resources around the Tarutung basin is a fault-controlled system as a result of deep circulation of fluids. Outside of the basin, the seismicity delineation and the focal mechanism correlate with the shape and the characteristics of the strike-slip Sumatran fault. Within the Tarutung basin, the seismicity is distributed more broadly which coincides with the margin of the basin. An extensional duplex system in the Tarutung basin is derived from the seismicity and focal mechanism analysis which is also consistent with the geological observations. The vertical distribution of the seismicity suggests the presence of a negative flower structure within the Tarutung basin.
N2  - Indonesien zählt zu den weltweit führenden Ländern bei der Nutzung von geothermischer Energie. Die geothermischen Energiequellen sind im Wesentlichen an den aktiven Vulkanismus gebunden, der durch die Prozesse an der indonesischen Subduktionszone verursacht wird. Darüber hinaus sind geotektonische Strukturen wie beispielsweise die Sumatra-Störung als verstärkende Faktoren für das geothermische Potenzial von Bedeutung. Bei der geophysikalischen Erkundung der indonesischen Geothermie-Ressourcen konzentrierte man sich bisher vor allem auf die Magnetotellurik. Passive Seismologie wurde dahingegen ausschließlich für die Überwachung von im Betrieb befindlichen Geothermie-Anlagen verwendet. Jüngste Untersuchungungen z.B. in Island und in den USA haben jedoch gezeigt, dass seismologische Verfahren bereits in der Erkundungsphase wichtige Informationen zu den physikalischen Eigenschaften, zum Spannungsfeld und zu möglichen Fluid- und Wärmetransportwegen liefern können. In der vorgelegten Doktorarbeit werden verschiedene moderne Methoden der passiven Seismologie verwendet, um beispielhaft ein neues, von der indonesischen Regierung für zukünftige geothermische Energiegewinnung ausgewiesenes Gebiet im nördlichen Teil Sumatras (Indonesien) zu erkunden. Die konkreten Ziele der Untersuchungen umfassten (1) die Ableitung von 3D Strukturmodellen der P- und S-Wellen Geschwindigkeiten (Parameter Vp und Vs), (2) die Bestimmung der Absorptionseigenschaften (Parameter Qp), und (3) die Kartierung und Charakterisierung von Störungssystemen auf der Grundlage der Seismizitätsverteilung und der Herdflächenlösungen. Für diese Zwecke habe ich zusammen mit Kollegen ein seismologisches Netzwerk in Tarutung (Sumatra) aufgebaut und über einen Zeitraum von 10 Monaten (Mai 2011 – Februar 2012) betrieben. Insgesamt wurden hierbei 42 Stationen (jeweils ausgestattet mit EDL-Datenlogger, 3-Komponenten, 1 Hz Seismometer) über eine Fläche von etwa 35 x 35 km verteilt. Mit dem Netzwerk wurden im gesamten Zeitraum 2568 lokale Erdbeben registriert. Die integrierte Betrachtung der Ergebnisse aus den verschiedenen Teilstudien (Tomographie, Erdbebenverteilung) erlaubt neue Einblicke in die generelle geologische Stukturierung sowie eine Eingrenzung von Bereichen mit einem erhöhten geothermischen Potenzial. Das tomographische Vp-Modell ermöglicht eine Bestimmung der Geometrie von Sedimentbecken entlang der Sumatra-Störung. Für die Geothermie besonders interessant ist der Bereich nordwestlich des Tarutung-Beckens. Die dort abgebildeten Anomalien (erhöhtes Vp/Vs, geringes Qp) habe ich als mögliche Aufstiegswege von warmen Fluiden interpretiert. Die scheinbar asymetrische Verteilung der Anomalien wird hierbei im Zusammenhang mit der Seismizitätsverteilung, der Geometrie der Beben-Bruchflächen, sowie struktur-geologischen Modellvorstellungen diskutiert. Damit werden wesentliche Informationen für die Planung einer zukünftigen geothermischen Anlage bereitgestellt.
T2  - Seismologische Untersuchungen eines Störungs-kontrollierten geothermischen Systems in Tarutung (Nord-Sumatra, Indonesien)
KW  - Tarutung
KW  - Sumatra Störung
KW  - Absorptionseigenschaften
KW  - seismische Geschwindigkeiten
KW  - Tarutung
KW  - Sumatra fault
KW  - attenuation tomography
KW  - velocity structure
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-72065
ER  - 
TY  - JOUR
A1  - Hartman, Jan F.
A1  - Gentz, Torben
A1  - Schiller, Amanda
A1  - Greule, Markus
A1  - Grossart, Hans-Peter
A1  - Ionescu, Danny
A1  - Keppler, Frank
A1  - Martinez-Cruz, Karla
A1  - Sepulveda-Jauregui, Armando
A1  - Isenbeck-Schroeter, Margot
T1  - A f ast and sensitive method for the continuous in situ determination of dissolved methane and its delta C-13-isotope ratio in surface waters
JF  - Limnology and Oceanography-methods
N2  - A fast and sensitive method for the continuous determination of methane (CH4) and its stable carbon isotopic values (delta C-13-CH4) in surface waters was developed by applying a vacuum to a gas/liquid exchange membrane and measuring the extracted gases by a portable cavity ring-down spectroscopy analyser (M-CRDS). The M-CRDS was calibrated and characterized for CH4 concentration and delta C-13-CH4 with synthetic water standards. The detection limit of the M-CRDS for the simultaneous determination of CH4 and delta C-13-CH4 is 3.6 nmol L-1 CH4. A measurement precision of CH4 concentrations and delta C-13-CH4 in the range of 1.1%, respectively, 1.7 parts per thousand (1 sigma) and accuracy (1.3%, respectively, 0.8 parts per thousand [1 sigma]) was achieved for single measurements and averaging times of 10 min. The response time tau of 57 +/- 5 s allow determination of delta C-13-CH4 values more than twice as fast than other methods. The demonstrated M-CRDS method was applied and tested for Lake Stechlin (Germany) and compared with the headspace-gas chromatography and fast membrane CH4 concentration methods. Maximum CH4 concentrations (577 nmol L-1) and lightest delta C-13-CH4 (-35.2 parts per thousand) were found around the thermocline in depth profile measurements. The M-CRDS-method was in good agreement with other methods. Temporal variations in CH4 concentration and delta C-13-CH4 obtained in 24 h measurements indicate either local methane production/oxidation or physical variations in the thermocline. Therefore, these results illustrate the need of fast and sensitive analyses to achieve a better understanding of different mechanisms and pathways of CH4 formation in aquatic environments.
Y1  - 2018
U6  - https://doi.org/10.1002/lom3.10244
SN  - 1541-5856
VL  - 16
IS  - 5
SP  - 273
EP  - 285
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Rach, Oliver
A1  - Kahmen, Ansgar
A1  - Brauer, Achim
A1  - Sachse, Dirk
T1  - A dual-biomarker approach for quantification of changes in relative humidity from sedimentary lipid D/H ratios
JF  - Climate of the past : an interactive open access journal of the European Geosciences Union
N2  - Past climatic change can be reconstructed from sedimentary archives by a number of proxies. However, few methods exist to directly estimate hydrological changes and even fewer result in quantitative data, impeding our understanding of the timing, magnitude and mechanisms of hydrological changes. Here we present a novel approach based on delta H-2 values of sedimentary lipid biomarkers in combination with plant physiological modeling to extract quantitative information on past changes in relative humidity. Our initial application to an annually laminated lacustrine sediment sequence from western Europe deposited during the Younger Dryas cold period revealed relative humidity changes of up to 15% over sub-centennial timescales, leading to major ecosystem changes, in agreement with palynological data from the region. We show that by combining organic geochemical methods and mechanistic plant physiological models on well characterized lacustrine archives it is possible to extract quantitative ecohydrological parameters from sedimentary lipid biomarker delta H-2 data.
Y1  - 2017
U6  - https://doi.org/10.5194/cp-13-741-2017
SN  - 1814-9324
SN  - 1814-9332
VL  - 13
SP  - 741
EP  - 757
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Jambrina-Enriquez, Margarita
A1  - Sachse, Dirk
A1  - Valero-Garces, Blas L.
T1  - A deglaciation and Holocene biomarker-based reconstruction of climate and environmental variability in NW Iberian Peninsula: the Sanabria Lake sequence
JF  - Journal of paleolimnolog
N2  - The molecular biomarker composition of two sediment cores from Sanabria Lake (NW Iberian Peninsula) and a survey of modern plants in the watershed provide a reconstruction of past vegetation and landscape dynamics since deglaciation. During a proglacial stage in Lake Sanabria (prior to 14.7 cal ka BP), very low biomarker concentration and carbon preference index (CPI) values similar to 1 suggest that the n-alkanes could have derived from eroded ancient sediment sources or older organic matter with high degree of maturity. During the Late glacial (14.7-11.7 cal ka BP) and the Holocene (last 11.7 cal ka BP) intervals with higher biomarker and triterpenoid concentrations (high %nC(29) , nC(31) alkanes), higher CPI and average carbon length (ACL), and lower P-aq (proportion of aquatic plants) are indicative of major contribution of vascular land plants from a more forested watershed (e.g. Mid Holocene period 7.0-4.0 cal ka BP). Lower biomarker concentrations (high %nC(27) alkanes), CPI and ACL values responded to short phases with decreased allochthonous contribution into the lake that correspond to centennial-scale periods of regional forest decline (e.g. 4-3 ka BP, Roman deforestation after 2.0 ka, and some phases of the LIA, seventeenth-nineteenth centuries). Human activities in the watershed were significant during early medieval times (1.3-1.0 cal ka BP) and since 1960 CE, in both cases associated with relatively higher productivity stages in the lake (lower biomarker and triterpenoid concentrations, high %nC(23) and %nC(31) respectively, lower ACL and CPI values and higher P-aq). The lipid composition of Sanabria Lake sediments indicates a major allochthonous (watershed-derived) contribution to the organic matter budget since deglaciation, and a dominant oligotrophic status during the lake history. The study constrains the climate and anthropogenic forcings and watershed versus lake sources in organic matter accumulation processes and helps to design conservation and management policies in mountain, oligotrophic lakes.
KW  - Plant n-alkanes
KW  - Lipid biomarker
KW  - Sanabria Lake
KW  - n-Alkanes
KW  - Holocene
KW  - Lateglacial
KW  - Iberian Peninsula
Y1  - 2016
U6  - https://doi.org/10.1007/s10933-016-9890-6
SN  - 0921-2728
SN  - 1573-0417
VL  - 56
SP  - 49
EP  - 66
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Kriegerowski, Marius
A1  - Petersen, Gesa Maria
A1  - Vasyura-Bathke, Hannes
A1  - Ohrnberger, Matthias
T1  - A Deep Convolutional Neural Network for Localization of Clustered Earthquakes Based on Multistation Full Waveforms
JF  - Seismological research letters
N2  - Earthquake localization is both a necessity within the field of seismology, and a prerequisite for further analysis such as source studies and hazard assessment. Traditional localization methods often rely on manually picked phases. We present an alternative approach using deep learning that once trained can predict hypocenter locations efficiently. In seismology, neural networks have typically been trained with either single-station records or based on features that have been extracted previously from the waveforms. We use three-component full-waveform records of multiple stations directly. This means no information is lost during preprocessing and preparation of the data does not require expert knowledge. The first convolutional layer of our deep convolutional neural network (CNN) becomes sensitive to features that characterize the waveforms it is trained on. We show that this layer can therefore additionally be used as an event detector. As a test case, we trained our CNN using more than 2000 earthquake swarm events from West Bohemia, recorded by nine local three-component stations. The CNN successfully located 908 validation events with standard deviations of 56.4 m in east-west, 123.8 m in north-south, and 136.3 m in vertical direction compared to a double-difference relocated reference catalog. The detector is sensitive to events with magnitudes down to M-L = -0.8 with 3.5% false positive detections.
Y1  - 2018
U6  - https://doi.org/10.1785/0220180320
SN  - 0895-0695
SN  - 1938-2057
VL  - 90
IS  - 2
SP  - 510
EP  - 516
PB  - Seismological Society of America
CY  - Albany
ER  - 
TY  - JOUR
A1  - Tötzke, Christian
A1  - Manke, Ingo
A1  - Gaiselmann, Gerd
A1  - Bohner, John
A1  - Müller, Bernd R.
A1  - Kupsch, Andreas
A1  - Hentschel, Manfred P.
A1  - Schmidt, Volker
A1  - Banhart, Jens
A1  - Lehnert, Werner
T1  - A dedicated compression device for high resolution X-ray tomography of compressed gas diffusion layers
JF  - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques
N2  - We present an experimental approach to study the three-dimensional microstructure of gas diffusion layer (GDL) materials under realistic compression conditions. A dedicated compression device was designed that allows for synchrotron-tomographic investigation of circular samples under well-defined compression conditions. The tomographic data provide the experimental basis for stochastic modeling of nonwoven GDL materials. A plain compression tool is used to study the fiber courses in the material at different compression stages. Transport relevant geometrical parameters, such as porosity, pore size, and tortuosity distributions, are exemplarily evaluated for a GDL sample in the uncompressed state and for a compression of 30 vol.%. To mimic the geometry of the flow-field, we employed a compression punch with an integrated channel-rib-profile. It turned out that the GDL material is homogeneously compressed under the ribs, however, much less compressed underneath the channel. GDL fibers extend far into the channel volume where they might interfere with the convective gas transport and the removal of liquid water from the cell. (C) 2015 AIP Publishing LLC.
Y1  - 2015
U6  - https://doi.org/10.1063/1.4918291
SN  - 0034-6748
SN  - 1089-7623
VL  - 86
IS  - 4
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Park, Jaeheung
A1  - Stolle, Claudia
A1  - Xiong, Chao
A1  - Lühr, Hermann
A1  - Pfaff, Robert F.
A1  - Buchert, Stephan
A1  - Martinis, Carlos R.
T1  - A dayside plasma depletion observed at midlatitudes during quiet geomagnetic conditions
JF  - Geophysical research letters
N2  - In this study we investigate a dayside, midlatitude plasma depletion (DMLPD) encountered on 22 May 2014 by the Swarm and GRACE satellites, as well as ground-based instruments. The DMLPD was observed near Puerto Rico by Swarm near 10 LT under quiet geomagnetic conditions at altitudes of 475-520 km and magnetic latitudes of similar to 25 degrees-30 degrees. The DMLPD was also revealed in total electron content observations by the Saint Croix station and by the GRACE satellites (430 km) near 16 LT and near the same geographic location. The unique Swarm constellation enables the horizontal tilt of the DMLPD to be measured (35 degrees clockwise from the geomagnetic east-west direction). Ground-based airglow images at Arecibo showed no evidence for plasma density depletions during the night prior to this dayside event. The C/NOFS equatorial satellite showed evidence for very modest plasma density depletions that had rotated into the morningside from nightside. However, the equatorial depletions do not appear related to the DMLPD, for which the magnetic apex height is about 2500 km. The origins of the DMLPD are unknown, but may be related to gravity waves.
Y1  - 2015
U6  - https://doi.org/10.1002/2014GL062655
SN  - 0094-8276
SN  - 1944-8007
VL  - 42
IS  - 4
SP  - 967
EP  - 974
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Brill, Fabio Alexander
A1  - Passuni Pineda, Silvia
A1  - Espichan Cuya, Bruno
A1  - Kreibich, Heidi
T1  - A data-mining approach towards damage modelling for El Nino events in Peru
JF  - Geomatics, natural hazards and risk
N2  - Compound natural hazards likeEl Ninoevents cause high damage to society, which to manage requires reliable risk assessments. Damage modelling is a prerequisite for quantitative risk estimations, yet many procedures still rely on expert knowledge, and empirical studies investigating damage from compound natural hazards hardly exist. A nationwide building survey in Peru after theEl Ninoevent 2017 - which caused intense rainfall, ponding water, flash floods and landslides - enables us to apply data-mining methods for statistical groundwork, using explanatory features generated from remote sensing products and open data. We separate regions of different dominant characteristics through unsupervised clustering, and investigate feature importance rankings for classifying damage via supervised machine learning. Besides the expected effect of precipitation, the classification algorithms select the topographic wetness index as most important feature, especially in low elevation areas. The slope length and steepness factor ranks high for mountains and canyons. Partial dependence plots further hint at amplified vulnerability in rural areas. An example of an empirical damage probability map, developed with a random forest model, is provided to demonstrate the technical feasibility.
KW  - Natural hazard
KW  - damage model
KW  - residential buildings
KW  - data-mining
KW  - remote
KW  - sensing
KW  - open data
Y1  - 2020
U6  - https://doi.org/10.1080/19475705.2020.1818636
SN  - 1947-5705
SN  - 1947-5713
VL  - 11
IS  - 1
SP  - 1966
EP  - 1990
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Lotze-Campen, Hermann
A1  - Verburg, Peter H.
A1  - Popp, Alexander
A1  - Lindner, Marcus
A1  - Verkerk, Pieter J.
A1  - Moiseyev, Alexander
A1  - Schrammeijer, Elizabeth
A1  - Helming, John
A1  - Tabeau, Andrzej
A1  - Schulp, Catharina J. E.
A1  - van der Zanden, Emma H.
A1  - Lavalle, Carlo
A1  - Batista e Silva, Filipe
A1  - Walz, Ariane
A1  - Bodirsky, Benjamin Leon
T1  - A cross-scale impact assessment of European nature protection policies under contrasting future socio-economic pathways
JF  - Regional environmental change
N2  - Protection of natural or semi-natural ecosystems is an important part of societal strategies for maintaining biodiversity, ecosystem services, and achieving overall sustainable development. The assessment of multiple emerging land use trade-offs is complicated by the fact that land use changes occur and have consequences at local, regional, and even global scale. Outcomes also depend on the underlying socio-economic trends. We apply a coupled, multi-scale modelling system to assess an increase in nature protection areas as a key policy option in the European Union (EU). The main goal of the analysis is to understand the interactions between policy-induced land use changes across different scales and sectors under two contrasting future socio-economic pathways. We demonstrate how complementary insights into land system change can be gained by coupling land use models for agriculture, forestry, and urban areas for Europe, in connection with other world regions. The simulated policy case of nature protection shows how the allocation of a certain share of total available land to newly protected areas, with specific management restrictions imposed, may have a range of impacts on different land-based sectors until the year 2040. Agricultural land in Europe is slightly reduced, which is partly compensated for by higher management intensity. As a consequence of higher costs, total calorie supply per capita is reduced within the EU. While wood harvest is projected to decrease, carbon sequestration rates increase in European forests. At the same time, imports of industrial roundwood from other world regions are expected to increase. Some of the aggregate effects of nature protection have very different implications at the local to regional scale in different parts of Europe. Due to nature protection measures, agricultural production is shifted from more productive land in Europe to on average less productive land in other parts of the world. This increases, at the global level, the allocation of land resources for agriculture, leading to a decrease in tropical forest areas, reduced carbon stocks, and higher greenhouse gas emissions outside of Europe. The integrated modelling framework provides a method to assess the land use effects of a single policy option while accounting for the trade-offs between locations, and between regional, European, and global scales.
KW  - Land use change
KW  - Integrated modelling
KW  - Cross-scale interaction
KW  - Nature protection
KW  - Impact assessment
Y1  - 2017
U6  - https://doi.org/10.1007/s10113-017-1167-8
SN  - 1436-3798
SN  - 1436-378X
VL  - 18
IS  - 3
SP  - 751
EP  - 762
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Schewe, Jacob
A1  - Levermann, Anders
A1  - Cheng, Hai
T1  - A critical humidity threshold for monsoon transitions
JF  - Climate of the past : an interactive open access journal of the European Geosciences Union
N2  - Monsoon systems around the world are governed by the so-called moisture-advection feedback. Here we show that, in a minimal conceptual model, this feedback implies a critical threshold with respect to the atmospheric specific humidity q(o) over the ocean adjacent to the monsoon region. If q(o) falls short of this critical value q(o)(c), monsoon rainfall over land cannot be sustained. Such a case could occur if evaporation from the ocean was reduced, e.g. due to low sea surface temperatures. Within the restrictions of the conceptual model, we estimate q(o)(c) from present-day reanalysis data for four major monsoon systems, and demonstrate how this concept can help understand abrupt variations in monsoon strength on orbital timescales as found in proxy records.
Y1  - 2012
U6  - https://doi.org/10.5194/cp-8-535-2012
SN  - 1814-9324
VL  - 8
IS  - 2
SP  - 535
EP  - 544
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Eberli, Gregor P.
A1  - Bernoulli, Daniel
A1  - Vecsei, Adam
A1  - Sekti, Rizky
A1  - Grasmueck, Mark
A1  - Lüdmann, Thomas
A1  - Anselmetti, Flavio S.
A1  - Mutti, Maria
A1  - Della Porta, Giovanna
T1  - A Cretaceous carbonate delta drift in the Montagna della Maiella, Italy
JF  - Sedimentology : the journal of the International Association of Sedimentologists
N2  - The Upper Cretaceous (Campanian-Maastrichtian) bioclastic wedge of the Orfento Formation in the Montagna della Maiella, Italy, is compared to newly discovered contourite drifts in the Maldives. Like the drift deposits in the Maldives, the Orfento Formation fills a channel and builds a Miocene delta-shaped and mounded sedimentary body in the basin that is similar in size to the approximately 350 km(2) large coarse-grained bioclastic Miocene delta drifts in the Maldives. The composition of the bioclastic wedge of the Orfento Formation is also exclusively bioclastic debris sourced from the shallow-water areas and reworked clasts of the Orfento Formation itself. In the near mud-free succession, age-diagnostic fossils are sparse. The depositional textures vary from wackestone to float-rudstone and breccia/conglomerates, but rocks with grainstone and rudstone textures are the most common facies. In the channel, lensoid convex-upward breccias, cross-cutting channelized beds and thick grainstone lobes with abundant scours indicate alternating erosion and deposition from a high-energy current. In the basin, the mounded sedimentary body contains lobes with a divergent progradational geometry. The lobes are built by decametre thick composite megabeds consisting of sigmoidal clinoforms that typically have a channelized topset, a grainy foreset and a fine-grained bottomset with abundant irregular angular clasts. Up to 30 m thick channels filled with intraformational breccias and coarse grainstones pinch out downslope between the megabeds. In the distal portion of the wedge, stacked grainstone beds with foresets and reworked intraclasts document continuous sediment reworking and migration. The bioclastic wedge of the Orfento Formation has been variously interpreted as a succession of sea-level controlled slope deposits, a shoaling shoreface complex, or a carbonate tidal delta. Current-controlled delta drifts in the Maldives, however, offer a new interpretation because of their similarity in architecture and composition. These similarities include: (i) a feeder channel opening into the basin; (ii) an excavation moat at the exit of the channel; (iii) an overall mounded geometry with an apex that is in shallower water depth than the source channel; (iv) progradation of stacked lobes; (v) channels that pinch out in a basinward direction; and (vi) smaller channelized intervals that are arranged in a radial pattern. As a result, the Upper Cretaceous (Campanian-Maastrichtian) bioclastic wedge of the Orfento Formation in the Montagna della Maiella, Italy, is here interpreted as a carbonate delta drift.
KW  - Carbonate contourite drift
KW  - delta drift
KW  - Maiella Mountains
KW  - Orfento Formation
KW  - prograding lobes
Y1  - 2019
U6  - https://doi.org/10.1111/sed.12590
SN  - 0037-0746
SN  - 1365-3091
VL  - 66
IS  - 4
SP  - 1266
EP  - 1301
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Bürger, Gerd
T1  - A counterexample to decomposing climate shifts and trends by weather types
JF  - International Journal of Climatology
N2  - The literature contains a sizable number of publications where weather types are used to decompose climate shifts or trends into contributions of frequency and mean of those types. They are all based on the product rule, that is, a transformation of a product of sums into a sum of products, the latter providing the decomposition. While there is nothing to argue about the transformation itself, its interpretation as a climate shift or trend decomposition is bound to fail. While the case of a climate shift may be viewed as an incomplete description of a more complex behaviour, trend decomposition indeed produces bogus trends, as demonstrated by a synthetic counterexample with well-defined trends in type frequency and mean. Consequently, decompositions based on that transformation, be it for climate shifts or trends, must not be used.
KW  - analysis
KW  - climate
KW  - statistical methods
Y1  - 2018
U6  - https://doi.org/10.1002/joc.5519
SN  - 0899-8418
SN  - 1097-0088
VL  - 38
IS  - 9
SP  - 3732
EP  - 3735
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Winter, Benjamin
A1  - Schneeberger, Klaus
A1  - Dung, N. V.
A1  - Huttenlau, M.
A1  - Achleitner, S.
A1  - Stötter, J.
A1  - Merz, Bruno
A1  - Vorogushyn, Sergiy
T1  - A continuous modelling approach for design flood estimation on sub-daily time scale
JF  - Hydrological sciences journal = Journal des sciences hydrologiques
N2  - Design flood estimation is an essential part of flood risk assessment. Commonly applied are flood frequency analyses and design storm approaches, while the derived flood frequency using continuous simulation has been getting more attention recently. In this study, a continuous hydrological modelling approach on an hourly time scale, driven by a multi-site weather generator in combination with a -nearest neighbour resampling procedure, based on the method of fragments, is applied. The derived 100-year flood estimates in 16 catchments in Vorarlberg (Austria) are compared to (a) the flood frequency analysis based on observed discharges, and (b) a design storm approach. Besides the peak flows, the corresponding runoff volumes are analysed. The spatial dependence structure of the synthetically generated flood peaks is validated against observations. It can be demonstrated that the continuous modelling approach can achieve plausible results and shows a large variability in runoff volume across the flood events.
KW  - derived flood frequency
KW  - continuous modelling
KW  - temporal disaggregation
KW  - flood hazard
KW  - synthetic flood events
Y1  - 2019
U6  - https://doi.org/10.1080/02626667.2019.1593419
SN  - 0262-6667
SN  - 2150-3435
VL  - 64
IS  - 5
SP  - 539
EP  - 554
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Wilke, Max
A1  - Appel, Karen
A1  - Vincze, Laszlo
A1  - Schmidt, Christian
A1  - Borchert, Manuela
A1  - Pascarelli, Sakura
T1  - A confocal set-up for micro-XRF and XAFS experiments using diamond-anvil cells
N2  - A confocal set-up is presented that improves micro-XRF and XAFS experiment with high-pressure e diamond-anvil cells (DACs) In this experiment a probing volume is defined by the focus of the incoming synchrotron radiation beam and that of a polycapillary X-ray half-lens with a very long working distance, which is placed in front of the fluorescence detector This set-up enhances the quality of the fluorescence and XAFS spectra, and thus the sensitivity for detecting elements at low concentrations. It efficiently suppresses signal from outside the sample chamber, which stems from elastic and inelastic scattering of the incoming beam by the diamond anvils as well as from excitation of fluorescence from the body of the DAC
Y1  - 2010
UR  - http://journals.iucr.org/s/journalhomepage.html
U6  - https://doi.org/10.1107/S0909049510023654
SN  - 0909-0495
ER  - 
TY  - JOUR
A1  - Wiggering, Hubert
A1  - Steinhardt, Uta
T1  - A conceptual model for site-specific agricultural land-use
JF  - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog
N2  - Land-use concepts provide decision support for the most efficient usage options according to sustainable development and multifunctionality requirements. However, developments in landscape-related, agricultural production schemes are primarily driven by economic benefits. Therefore, most agricultural land-use concepts tackle particular problems or interests and lack a systemic perspective. As a result, we discuss a conceptual model for future site-specific agricultural land-use with an inbuilt requirement for adequate experimental sites to enable monitoring systems for a new generation of ecosystem models and for new approaches to address science-stakeholder interactions.
KW  - Site-specific agricultural land-use
KW  - Concept of differentiated land use
KW  - Sustainable land use
KW  - Multifunctionality
KW  - Modeling tools for decision-making
Y1  - 2015
U6  - https://doi.org/10.1016/j.ecolmodel.2014.08.011
SN  - 0304-3800
SN  - 1872-7026
VL  - 295
SP  - 42
EP  - 46
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Zhang, Zhuo-dong
A1  - Wieland, Ralf
A1  - Reiche, Matthias
A1  - Funk, Roger
A1  - Hoffmann, Carsten
A1  - Li, Yong
A1  - Sommer, Michael
T1  - A computational fluid dynamics model for wind simulation: model implementation and experimental validation
JF  - Journal of Zhejiang University : an international journal ; Science A, Applied physics & engineering : an international applied physics & engineering journal
N2  - To provide physically based wind modelling for wind erosion research at regional scale, a 3D computational fluid dynamics (CFD) wind model was developed. The model was programmed in C language based on the Navier-Stokes equations, and it is freely available as open source. Integrated with the spatial analysis and modelling tool (SAMT), the wind model has convenient input preparation and powerful output visualization. To validate the wind model, a series of experiments was conducted in a wind tunnel. A blocking inflow experiment was designed to test the performance of the model on simulation of basic fluid processes. A round obstacle experiment was designed to check if the model could simulate the influences of the obstacle on wind field. Results show that measured and simulated wind fields have high correlations, and the wind model can simulate both the basic processes of the wind and the influences of the obstacle on the wind field. These results show the high reliability of the wind model. A digital elevation model (DEM) of an area (3800 m long and 1700 m wide) in the Xilingele grassland in Inner Mongolia (autonomous region, China) was applied to the model, and a 3D wind field has been successfully generated. The clear implementation of the model and the adequate validation by wind tunnel experiments laid a solid foundation for the prediction and assessment of wind erosion at regional scale.
KW  - Wind model
KW  - Computational fluid dynamics (CFD)
KW  - Wind erosion
KW  - Wind tunnel experiments
KW  - Spatial analysis and modelling tool (SAMT)
KW  - Open source
Y1  - 2012
U6  - https://doi.org/10.1631/jzus.A1100231
SN  - 1673-565X
VL  - 13
IS  - 4
SP  - 274
EP  - 283
PB  - Zhejiang University Press
CY  - Hangzou
ER  - 
TY  - JOUR
A1  - Arboleda-Zapata, Mauricio
A1  - Guillemoteau, Julien
A1  - Tronicke, Jens
T1  - A comprehensive workflow to analyze ensembles of globally inverted 2D electrical resistivity models
JF  - Journal of applied geophysics
N2  - Electrical resistivity tomography (ERT) aims at imaging the subsurface resistivity distribution and provides valuable information for different geological, engineering, and hydrological applications. To obtain a subsurface resistivity model from measured apparent resistivities, stochastic or deterministic inversion procedures may be employed. Typically, the inversion of ERT data results in non-unique solutions; i.e., an ensemble of different models explains the measured data equally well. In this study, we perform inference analysis of model ensembles generated using a well-established global inversion approach to assess uncertainties related to the nonuniqueness of the inverse problem. Our interpretation strategy starts by establishing model selection criteria based on different statistical descriptors calculated from the data residuals. Then, we perform cluster analysis considering the inverted resistivity models and the corresponding data residuals. Finally, we evaluate model uncertainties and residual distributions for each cluster. To illustrate the potential of our approach, we use a particle swarm optimization (PSO) algorithm to obtain an ensemble of 2D layer-based resistivity models from a synthetic data example and a field data set collected in Loon-Plage, France. Our strategy performs well for both synthetic and field data and allows us to extract different plausible model scenarios with their associated uncertainties and data residual distributions. Although we demonstrate our workflow using 2D ERT data and a PSObased inversion approach, the proposed strategy is general and can be adapted to analyze model ensembles generated from other kinds of geophysical data and using different global inversion approaches.
KW  - Near-surface geophysics
KW  - Electrical resistivity tomography
KW  - Non-uniqueness
KW  - Global inversion
KW  - Particle swarm optimization
KW  - Ensemble
KW  - analysis
Y1  - 2021
U6  - https://doi.org/10.1016/j.jappgeo.2021.104512
SN  - 0926-9851
SN  - 1879-1859
VL  - 196
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Guntu, Ravikumar
A1  - Banerjee, Abhirup
A1  - Gadhawe, Mayuri Ashokrao
A1  - Marwan, Norbert
T1  - A complex network approach to study the extreme precipitation patterns in a river basin
JF  - Chaos : an interdisciplinary journal of nonlinear science
N2  - The quantification of spatial propagation of extreme precipitation events is vital in water resources planning and disaster mitigation. However, quantifying these extreme events has always been challenging as many traditional methods are insufficient to capture the nonlinear interrelationships between extreme event time series. Therefore, it is crucial to develop suitable methods for analyzing the dynamics of extreme events over a river basin with a diverse climate and complicated topography. Over the last decade, complex network analysis emerged as a powerful tool to study the intricate spatiotemporal relationship between many variables in a compact way. In this study, we employ two nonlinear concepts of event synchronization and edit distance to investigate the extreme precipitation pattern in the Ganga river basin. We use the network degree to understand the spatial synchronization pattern of extreme rainfall and identify essential sites in the river basin with respect to potential prediction skills. The study also attempts to quantify the influence of precipitation seasonality and topography on extreme events. The findings of the study reveal that (1) the network degree is decreased in the southwest to northwest direction, (2) the timing of 50th percentile precipitation within a year influences the spatial distribution of degree, (3) the timing is inversely related to elevation, and (4) the lower elevation greatly influences connectivity of the sites. The study highlights that edit distance could be a promising alternative to analyze event-like data by incorporating event time and amplitude and constructing complex networks of climate extremes.
Y1  - 2022
U6  - https://doi.org/10.1063/5.0072520
SN  - 1054-1500
SN  - 1089-7682
VL  - 32
IS  - 1
PB  - American Institute of Physics
CY  - Woodbury, NY
ER  - 
TY  - JOUR
A1  - Boers, Niklas
A1  - Goswami, Bedartha
A1  - Ghil, Michael
T1  - A complete representation of uncertainties in layer-counted paleoclimatic archives
JF  - Climate of the past : an interactive open access journal of the European Geosciences Union
N2  - Accurate time series representation of paleoclimatic proxy records is challenging because such records involve dating errors in addition to proxy measurement errors. Rigorous attention is rarely given to age uncertainties in paleoclimatic research, although the latter can severely bias the results of proxy record analysis. Here, we introduce a Bayesian approach to represent layer-counted proxy records - such as ice cores, sediments, corals, or tree rings - as sequences of probability distributions on absolute, error-free time axes. The method accounts for both proxy measurement errors and uncertainties arising from layer-counting-based dating of the records. An application to oxygen isotope ratios from the North Greenland Ice Core Project (NGRIP) record reveals that the counting errors, although seemingly small, lead to substantial uncertainties in the final representation of the oxygen isotope ratios. In particular, for the older parts of the NGRIP record, our results show that the total uncertainty originating from dating errors has been seriously underestimated. Our method is next applied to deriving the overall uncertainties of the Suigetsu radiocarbon comparison curve, which was recently obtained from varved sediment cores at Lake Suigetsu, Japan. This curve provides the only terrestrial radiocarbon comparison for the time interval 12.5-52.8 kyr BP. The uncertainties derived here can be readily employed to obtain complete error estimates for arbitrary radiometrically dated proxy records of this recent part of the last glacial interval.
Y1  - 2017
U6  - https://doi.org/10.5194/cp-13-1169-2017
SN  - 1814-9324
SN  - 1814-9332
VL  - 13
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Pilz, Marco
A1  - Parolai, Stefano
A1  - Leyton, Felipe
A1  - Campos, Jaime
A1  - Zschau, Jochen
T1  - A comparison of site response techniques using earthquake data and ambient seismic noise analysis in the large urban areas of Santiago de Chile
N2  - Situated in an active tectonic region, Santiago de Chile, the country's capital with more than six million inhabitants, faces tremendous earthquake risk. Macroseismic data for the 1985 Valparaiso event show large variations in the distribution of damage to buildings within short distances, indicating strong effects of local sediments on ground motion. Therefore, a temporary seismic network was installed in the urban area for recording earthquake activity and a study was carried out aiming to estimate site amplification derived from horizontal-to- vertical (H/V) spectral ratios from earthquake data (EHV) and ambient noise (NHV), as well as using the standard spectral ratio (SSR) technique with a nearby reference station located on igneous rock. The results lead to the following conclusions: The analysis of earthquake data shows significant dependence on the local geological structure with respect to amplitude and duration. An amplification of ground motion at frequencies higher than the fundamental one can be found. This amplification would not be found when looking at NHV ratios alone. The analysis of NHV spectral ratios shows that they can only provide a lower bound in amplitude for site amplification. P-wave site responses always show lower amplitudes than those derived by S waves, and sometimes even fail to provide some frequencies of amplification. No variability in terms of time and amplitude is observed in the analysis of the H/V ratio of noise. Due to the geological conditions in some parts of the investigated area, the fundamental resonance frequency of a site is difficult to estimate following standard criteria proposed by the SESAME consortium, suggesting that these are too restrictive under certain circumstances.
Y1  - 2009
UR  - http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-246X
U6  - https://doi.org/10.1111/j.1365-246X.2009.04195.x
SN  - 0956-540X
ER  - 
TY  - THES
A1  - Pilz, Marco
T1  - A comparison of proxies for seismic site conditions and amplification for the large urban area of Santiago de Chile
T1  - Ein Vergleich seismischer Parameter für die Standort- und Verstärkungsabschätzung im Stadtgebiet von Santiago de Chile
N2  - Situated in an active tectonic region, Santiago de Chile, the country´s capital with more than six million inhabitants, faces tremendous earthquake hazard. Macroseismic data for the 1985 Valparaiso and the 2010 Maule events show large variations in the distribution of damage to buildings within short distances indicating strong influence of local sediments and the shape of the sediment-bedrock interface on ground motion. Therefore, a temporary seismic network was installed in the urban area for recording earthquake activity, and a study was carried out aiming to estimate site amplification derived from earthquake data and ambient noise. The analysis of earthquake data shows significant dependence on the local geological structure with regards to amplitude and duration. Moreover, the analysis of noise spectral ratios shows that they can provide a lower bound in amplitude for site amplification and, since no variability in terms of time and amplitude is observed, that it is possible to map the fundamental resonance frequency of the soil for a 26 km x 12 km area in the northern part of the Santiago de Chile basin. By inverting the noise spectral rations, local shear wave velocity profiles could be derived under the constraint of the thickness of the sedimentary cover which had previously been determined by gravimetric measurements. The resulting 3D model was derived by interpolation between the single shear wave velocity profiles and shows locally good agreement with the few existing velocity profile data, but allows the entire area, as well as deeper parts of the basin, to be represented in greater detail. The wealth of available data allowed further to check if any correlation between the shear wave velocity in the uppermost 30 m (vs30) and the slope of topography, a new technique recently proposed by Wald and Allen (2007), exists on a local scale. While one lithology might provide a greater scatter in the velocity values for the investigated area, almost no correlation between topographic gradient and calculated vs30 exists, whereas a better link is found between vs30 and the local geology. When comparing the vs30 distribution with the MSK intensities for the 1985 Valparaiso event it becomes clear that high intensities are found where the expected vs30 values are low and over a thick sedimentary cover. Although this evidence cannot be generalized for all possible earthquakes, it indicates the influence of site effects modifying the ground motion when earthquakes occur well outside of the Santiago basin. Using the attained knowledge on the basin characteristics, simulations of strong ground motion within the Santiago Metropolitan area were carried out by means of the spectral element technique. The simulation of a regional event, which has also been recorded by a dense network installed in the city of Santiago for recording aftershock activity following the 27 February 2010 Maule earthquake, shows that the model is capable to realistically calculate ground motion in terms of amplitude, duration, and frequency and, moreover, that the surface topography and the shape of the sediment bedrock interface strongly modify ground motion in the Santiago basin. An examination on the dependency of ground motion on the hypocenter location for a hypothetical event occurring along the active San Ramón fault, which is crossing the eastern outskirts of the city, shows that the unfavorable interaction between fault rupture, radiation mechanism, and complex geological conditions in the near-field may give rise to large values of peak ground velocity and therefore considerably increase the level of seismic risk for Santiago de Chile.
N2  - Aufgrund ihrer Lage in einem tektonisch aktiven Gebiet ist Santiago de Chile, die Hauptstadt des Landes mit mehr als sechs Millionen Einwohnern, einer großen Erdbebengefährdung ausgesetzt. Darüberhinaus zeigen makroseismische Daten für das 1985 Valparaiso- und das 2010 Maule-Erdbeben eine räumlich unterschiedliche Verteilung der an den Gebäuden festgestellten Schäden; dies weist auf einen starken Einfluss der unterliegenden Sedimentschichten und der Gestalt der Grenzfläche zwischen den Sedimenten und dem Festgestein auf die Bodenbewegung hin. Zu diesem Zweck wurde in der Stadt ein seismisches Netzwerk für die Aufzeichnung der Bodenbewegung installiert, um die auftretende Untergrundverstärkung mittels Erdbebendaten und seismischem Rauschen abzuschätzen. Dabei zeigt sich für die Erdbebendaten eine deutliche Abhängigkeit von der Struktur des Untergrunds hinsichtlich der Amplitude der Erschütterung und ihrer Dauer. Die Untersuchung der aus seismischem Rauschen gewonnenen horizontal-zu-vertikal-(H/V) Spektral-verhältnisse zeigt, dass diese Ergebnisse nur einen unteren Grenzwert für die Bodenverstärkung liefern können. Weil jedoch andererseits keine zeitliche Veränderung bei der Gestalt dieser Spektralverhältnisse festgestellt werden konnte, erlauben die Ergebnisse ferner, die Resonanzfrequenz des Untergrundes für ein 26 km x 12 km großes Gebiet im Nordteil der Stadt zu bestimmen. Unter Zuhilfenahme von Informationen über die Dicke der Sedimentschichten, welche im vorhinein schon durch gravimetrische Messungen bestimmt worden war, konnten nach Inversion der H/V-Spektralverhältnisse lokale Scherwellengeschwindigkeitsprofile und nach Interpolation zwischen den einzelnen Profilen ein dreidimensionales Modell berechnet werden. Darüberhinaus wurde mit den verfügbaren Daten untersucht, ob auf lokaler Ebene ein Zusammenhang zwischen der mittleren Scherwellengeschwindigkeit in den obersten 30 m (vs30) und dem Gefälle existiert, ein Verfahren, welches kürzlich von Wald und Allen (2007) vorgestellt wurde. Da für jede lithologische Einheit eine starke Streuung für die seismischen Geschwindigkeiten gefunden wurde, konnte kein Zusammenhang zwischen dem Gefälle und vs30 hergestellt werden; demgegenüber besteht zumindest ein tendenzieller Zusammenhang zwischen vs30 und der unterliegenden Geologie. Ein Vergleich der Verteilung von vs30 mit den MKS-Intensitäten für das 1985 Valparaiso-Erdbeben in Santiago zeigt, dass hohe Intensitätswerte vor allem in Bereichen geringer vs30-Werte und dicker Sedimentschichten auftraten. Weiterhin ermöglichte die Kenntnis über das Sedimentbeckens Simulationen der Bodenbewegung mittels eines spektralen-Elemente-Verfahrens. Die Simulation eines regionalen Erdbebens, welches auch von einem dichten seismischen Netzwerk aufgezeichnet wurde, das im Stadtgebiet von Santiago infolge des Maule-Erdbebens am 27. Februar 2010 installiert wurde, zeigt, dass das Modell des Sedimentbeckens realistische Berechnungen hinsichtlich Amplitude, Dauer und Frequenz erlaubt und die ausgeprägte Topographie in Verbindung mit der Form der Grenzfläche zwischen den Sedimenten und dem Festgestein starken Einfluss auf die Bodenbewegung haben. Weitere Untersuchungen zur Abhängigkeit der Bodenerschütterung von der Position des Hypozentrums für ein hypothetisches Erdbeben an der San Ramón-Verwerfung, welche die östlichen Vororte der Stadt kreuzt, zeigen, dass die ungünstige Wechselwirkung zwischen dem Verlauf des Bruchs, der Abstrahlung der Energie und der komplexen geologischen Gegebenheiten hohe Werte bei der maximalen Bodengeschwindigkeit erzeugen kann. Dies führt zu einer signifikanten Zunahme des seismischen Risikos für Santiago de Chile.
KW  - Standorteffekte
KW  - seismisches Rauschen
KW  - Sedimentbecken
KW  - Simulation
KW  - site effects
KW  - seismic noise
KW  - sedimentary basin
KW  - simulation
Y1  - 2010
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-52961
ER  - 
TY  - JOUR
A1  - Forbrich, Inke
A1  - Kutzbach, Lars
A1  - Hormann, Annabell
A1  - Wilmking, Martin
T1  - A comparison of linear and exponential regression for estimating diffusive CH4 fluxes by closed-chambers in peatlands
N2  - The closed-chamber method is the most common approach to determine CH4 fluxes in peatlands. The concentration change in the chamber is monitored over time, and the flux is usually calculated by the slope of a linear regression function. Theoretically, the gas exchange cannot be constant over time but has to decrease, when the concentration gradient between chamber headspace and soil air decreases. In this study, we test whether we can detect this non- linearity in the concentration change during the chamber closure with six air samples. We expect generally a low concentration gradient on dry sites (hummocks) and thus the occurrence of exponential concentration changes in the chamber due to a quick equilibrium of gas concentrations between peat and chamber headspace. On wet (flarks) and sedge- covered sites (lawns), we expect a high gradient and near-linear concentration changes in the chamber. To evaluate these model assumptions, we calculate both linear and exponential regressions for a test data set (n = 597) from a Finnish mire. We use the Akaike Information Criterion with small sample second order bias correction to select the best-fitted model. 13.6%, 19.2% and 9.8% of measurements on hummocks, lawns and flarks, respectively, were best fitted with an exponential regression model. A flux estimation derived from the slope of the exponential function at the beginning of the chamber closure can be significantly higher than using the slope of the linear regression function. Non-linear concentration-overtime curves occurred mostly during periods of changing water table. This could be due to either natural processes or chamber artefacts, e.g. initial pressure fluctuations during chamber deployment. To be able to exclude either natural processes or artefacts as cause of non-linearity, further information, e.g. CH4 concentration profile measurements in the peat, would be needed. If this is not available, the range of uncertainty can be substantial. We suggest to use the range between the slopes of the exponential regression at the beginning and at the end of the closure time as an estimate of the overall uncertainty.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00380717
U6  - https://doi.org/10.1016/j.soilbio.2009.12.004
SN  - 0038-0717
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  - Hudson, Paul
T1  - A comparison of definitions of affordability for flood risk adaption measures
BT  - a case study of current and future risk-based flood insurance premiums in Europe
JF  - Mitigation and adaptation strategies for global change : an international journal devoted to scientific, engineering, socio-economic and policy responses to environmental change
N2  - Risk-based insurance is a commonly proposed and discussed flood risk adaptation mechanism in policy debates across the world such as in the United Kingdom and the United States of America. However, both risk-based premiums and growing risk pose increasing difficulties for insurance to remain affordable. An empirical concept of affordability is required as the affordability of adaption strategies is an important concern for policymakers, yet such a concept is not often examined. Therefore, a robust metric with a commonly acceptable affordability threshold is required. A robust metric allows for a previously normative concept to be quantified in monetary terms, and in this way, the metric is rendered more suitable for integration into public policy debates. This paper investigates the degree to which risk-based flood insurance premiums are unaffordable in Europe. In addition, this paper compares the outcomes generated by three different definitions of unaffordability in order to investigate the most robust definition. In doing so, the residual income definition was found to be the least sensitive to changes in the threshold. While this paper focuses on Europe, the selected definition can be employed elsewhere in the world and across adaption measures in order to develop a common metric for indicating the potential unaffordability problem.
KW  - Flood risk
KW  - Insurance
KW  - Affordability
KW  - Climate change
KW  - Adaptation
KW  - Public policy
Y1  - 2018
U6  - https://doi.org/10.1007/s11027-017-9769-5
SN  - 1381-2386
SN  - 1573-1596
VL  - 23
IS  - 7
SP  - 1019
EP  - 1038
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Spekkers, Matthieu
A1  - Roezer, Viktor
A1  - Thieken, Annegret
A1  - ten Veldhuis, Marie-Claire
A1  - Kreibich, Heidi
T1  - A comparative survey of the impacts of extreme rainfall in two international case studies
JF  - Natural hazards and earth system sciences
Y1  - 2017
U6  - https://doi.org/10.5194/nhess-17-1337-2017
SN  - 1561-8633
VL  - 17
SP  - 1337
EP  - 1355
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - van zanten, Boris T.
A1  - Zasada, Ingo
A1  - Koetse, Mark J.
A1  - Ungaro, Fabrizio
A1  - Hafner, Kati
A1  - Verburg, Peter H.
T1  - A comparative approach to assess the contribution of landscape features to aesthetic and recreational values in agricultural landscapes
JF  - Ecosystem Services : Science, Policy and Practice
N2  - The importance of cultural ecosystem services in agricultural landscapes is increasingly recognized as agricultural scale enlargement and abandonment affect aesthetic and recreational values of agricultural landscapes. Landscape preference studies addressing these type of values often yield context-specific outcomes, limiting the applicability of their outcomes in landscape policy. Our approach measures the relative importance of landscape features across agricultural landscapes. This approach was applied in the agricultural landscapes of Winterswijk, The Netherlands (n=191) and the Markische Schweiz, Germany (n=113) among visitors in the agricultural landscape. We set up a parallel designed choice experiment, using regionally specific, photorealistic visualizations of four comparable landscape attributes. In the Dutch landscape visitors highly value hedgerows and tree lines, whereas groups of trees and crop diversity are highly valued in the German landscape. Furthermore, we find that differences in relative preference for landscape attributes are, to some extent, explained by socio-cultural background variables such as education level and affinity with agriculture of the visitors. This approach contributes to a better understanding of the cross-regional variation of aesthetic and recreational values and how these values relate to characteristics of the agricultural landscape, which could support the integration of cultural services in landscape policy. (C) 2015 Elsevier B.V. All rights reserved.
KW  - Cultural ecosystem services
KW  - Landscape preferences
KW  - Comparative study
KW  - Landscape aesthetics
KW  - Landscape values
KW  - Agricultural landscape
Y1  - 2016
U6  - https://doi.org/10.1016/j.ecoser.2015.11.011
SN  - 2212-0416
VL  - 17
SP  - 87
EP  - 98
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Salazar, S.
A1  - Frances, F.
A1  - Komma, J.
A1  - Blume, Theresa
A1  - Francke, Till
A1  - Bronstert, Axel
A1  - Blöschl, Günter
T1  - A comparative analysis of the effectiveness of flood management measures based on the concept of "retaining water in the landscape" in different European hydro-climatic regions
JF  - Natural hazards and earth system sciences
N2  - In this paper, we analyse the effectiveness of flood management measures based on the concept known as "retaining water in the landscape". The investigated measures include afforestation, micro-ponds and small-reservoirs. A comparative and model-based methodological approach has been developed and applied for three meso-scale catchments located in different European hydro-climatological regions: Poyo (184 km(2)) in the Spanish Mediterranean, Upper Iller (954 km(2)) in the German Alps and Kamp (621 km(2)) in Northeast-Austria representing the Continental hydro-climate. This comparative analysis has found general similarities in spite of the particular differences among studied areas. In general terms, the flood reduction through the concept of "retaining water in the landscape" depends on the following factors: the storage capacity increase in the catchment resulting from such measures, the characteristics of the rainfall event, the antecedent soil moisture condition and the spatial distribution of such flood management measures in the catchment. In general, our study has shown that, this concept is effective for small and medium events, but almost negligible for the largest and less frequent floods: this holds true for all different hydro-climatic regions, and with different land-use, soils and morphological settings.
Y1  - 2012
U6  - https://doi.org/10.5194/nhess-12-3287-2012
SN  - 1561-8633
VL  - 12
IS  - 11
SP  - 3287
EP  - 3306
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Maslin, Mark
A1  - Trauth, Martin H.
A1  - Christensen, B.
T1  - A changing climate for human evolution
Y1  - 2005
SN  - 0016-8556
ER  - 
TY  - JOUR
A1  - Lappe, Michael
A1  - Kallmeyer, Jens
T1  - A cell extraction method for oily sediments
JF  - Frontiers in microbiology
N2  - Hydrocarbons can be found in many different habitats and represent an important carbon source for microbes. As fossil fuels, they are also an important economical resource and through natural seepage or accidental release they can be major pollutants. DNA-specific stains and molecular probes bind to hydrocarbons, causing massive background fluorescence, thereby hampering cell enumeration. The cell extraction procedure of Kallmeyer et al. (2008) separates the cells from the sediment matrix. In principle, this technique can also be used to separate cells from oily sediments, but it was not originally optimized for this application. Here we present a modified extraction method in which the hydrocarbons are removed prior to cell extraction. Due to the reduced background fluorescence the microscopic image becomes clearer, making cell identification, and enumeration much easier. Consequently, the resulting cell counts from oily samples treated according to our new protocol are significantly higher than those treated according to Kallmeyer et al. (2008). We tested different amounts of a variety of solvents for their ability to remove hydrocarbons and found that n-hexane and in samples containing more mature oils methanol, delivered the best results. However, as solvents also tend to lyse cells, it was important to find the optimum solvent to sample ratio, at which hydrocarbon extraction is maximized and cell lysis minimized. A volumetric ratio of 1:2-1:5 between a formalin-fixed sediment slurry and solvent delivered highest cell counts. Extraction efficiency was around 30-50% and was checked on both oily samples spiked with known amounts of E. coli cells and oil-free samples amended with fresh and biodegraded oil. The method provided reproducible results on samples containing very different kinds of oils with regard to their degree of biodegradation. For strongly biodegraded oil MeOH turned out to be the most appropriate solvent, whereas for less biodegraded samples n-hexane delivered best results.
KW  - cell enumeration
KW  - hydrocarbons
KW  - cell separation
KW  - subsurface microbiology
Y1  - 2011
U6  - https://doi.org/10.3389/fmicb.2011.00233
SN  - 1664-302X
VL  - 2
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  - 
TY  - THES
A1  - Swierczynski, Tina
T1  - A 7000 yr runoff chronology from varved sediments of Lake Mondsee (Upper Austria)
T1  - Eine 7000-jährige Abflusschronologie anhand von warvierten Sedimenten des Mondsees (Oberösterreich)
N2  - The potential increase in frequency and magnitude of extreme floods is currently discussed in terms of global warming and the intensification of the hydrological cycle. The profound knowledge of past natural variability of floods is of utmost importance in order to assess flood risk for the future. Since instrumental flood series cover only the last ~150 years, other approaches to reconstruct historical and pre-historical flood events are needed. Annually laminated (varved) lake sediments are meaningful natural geoarchives because they provide continuous records of environmental changes > 10000 years down to a seasonal resolution. Since lake basins additionally act as natural sediment traps, the riverine sediment supply, which is preserved as detrital event layers in the lake sediments, can be used as a proxy for extreme discharge events. Within my thesis I examined a ~ 8.50 m long sedimentary record from the pre-Alpine Lake Mondsee (Northeast European Alps), which covered the last 7000 years. This sediment record consists of calcite varves and intercalated detrital layers, which range in thickness from 0.05 to 32 mm. Detrital layer deposition was analysed by a combined method of microfacies analysis via thin sections, Scanning Electron Microscopy (SEM), μX-ray fluorescence (μXRF) scanning and magnetic susceptibility. This approach allows characterizing individual detrital event layers and assigning a corresponding input mechanism and catchment. Based on varve counting and controlled by 14C age dates, the main goals of this thesis are (i) to identify seasonal runoff processes, which lead to significant sediment supply from the catchment into the lake basin and (ii) to investigate flood frequency under changing climate boundary conditions. This thesis follows a line of different time slices, presenting an integrative approach linking instrumental and historical flood data from Lake Mondsee in order to evaluate the flood record inferred from Lake Mondsee sediments. The investigation of eleven short cores covering the last 100 years reveals the abundance of 12 detrital layers. Therein, two types of detrital layers are distinguished by grain size, geochemical composition and distribution pattern within the lake basin. Detrital layers, which are enriched in siliciclastic and dolomitic material, reveal sediment supply from the Flysch sediments and Northern Calcareous Alps into the lake basin. These layers are thicker in the northern lake basin (0.1-3.9 mm) and thinner in the southern lake basin (0.05-1.6 mm). Detrital layers, which are enriched in dolomitic components forming graded detrital layers (turbidites), indicate the provenance from the Northern Calcareous Alps. These layers are generally thicker (0.65-32 mm) and are solely recorded within the southern lake basin. In comparison with instrumental data, thicker graded layers result from local debris flow events in summer, whereas thin layers are deposited during regional flood events in spring/summer. Extreme summer floods as reported from flood layer deposition are principally caused by cyclonic activity from the Mediterranean Sea, e.g. July 1954, July 1997 and August 2002. During the last two millennia, Lake Mondsee sediments reveal two significant flood intervals with decadal-scale flood episodes, during the Dark Ages Cold Period (DACP) and the transition from the Medieval Climate Anomaly (MCA) into the Little Ice Age (LIA) suggesting a linkage of transition to climate cooling and summer flood recurrences in the Northeastern Alps. In contrast, intermediate or decreased flood episodes appeared during the MWP and the LIA. This indicates a non-straightforward relationship between temperature and flood recurrence, suggesting higher cyclonic activity during climate transition in the Northeast Alps. The 7000-year flood chronology reveals 47 debris flows and 269 floods, with increased flood activity shifting around 3500 and 1500 varve yr BP (varve yr BP = varve years before present, before present = AD 1950). This significant increase in flood activity shows a coincidence with millennial-scale climate cooling that is reported from main Alpine glacier advances and lower tree lines in the European Alps since about 3300 cal. yr BP (calibrated years before present). Despite relatively low flood occurrence prior to 1500 varve yr BP, floods at Lake Mondsee could have also influenced human life in early Neolithic lake dwellings (5750-4750 cal. yr BP). While the first lake dwellings were constructed on wetlands, the later lake dwellings were built on piles in the water suggesting an early flood risk adaptation of humans and/or a general change of the Late Neolithic Culture of lake-dwellers because of socio-economic reasons. However, a direct relationship between the final abandonment of the lake dwellings and higher flood frequencies is not evidenced.
N2  - Ein verstärktes Auftreten von Hochwassern, sowohl in ihrer Häufigkeit als auch in ihrer Frequenz, wird im Zuge der Klimaerwärmung und einer möglichen Intensivierung des hydrologischen Kreislaufs diskutiert. Die Kenntnis über die natürliche Variabilität von Hochwasserereignissen ist dabei eine grundlegende Voraussetzung, um die Hochwassergefahr für die Zukunft abschätzen zu können. Da instrumentelle Hochwasserzeitreihen meist nur die letzten 150 Jahre abbilden sind andere Methoden erforderlich, um das Auftreten von historischen und prä-historischen Hochwassern festzustellen. Jährlich laminierte (warvierte) Seesedimente sind bedeutende natürliche Archive, denn sie liefern kontinuierliche Zeitreihen > 10000 Jahre mit einer bis zur saisonalen Auflösung. Seebecken stellen natürliche Sedimentfallen dar, wobei eingetragenes Flusssediment in den Seesedimenten als eine distinkte detritische Lage aufgezeichnet wird, und daher zur Rekonstruktion von extremen Abflussereignissen genutzt werden. Im Rahmen meiner Doktorarbeit habe ich einen 8.50 m langen Sedimentkern aus dem Mondsee (Nordostalpen) untersucht, welcher die letzten 7000 Jahre abdeckt. Dieser Sedimentkern besteht aus Kalzitwarven und eingeschalteten detritischen Lagen mit einer Mächtigkeit von 0.05-32 mm. Detritische Lagen wurden mit Hilfe einer kombinierten Methode untersucht: Mikrofaziesanalyse, Rasterelektronenmikroskopie, Röntgenfluoreszenzanalyse (µXRF) und magnetische Suszeptibilität. Dieser Ansatz ermöglicht die Charakterisierung der einzelnen detritischen Lagen bezüglich der Eintragsprozesse und die Lokalisierung des Einzugsgebietes. Auf Grundlage der Warvenzählung und 14C Datierungen sind die wichtigsten Ziele dieser Arbeit: (i) die Identifizierung der Eintragsprozesse, welche zu einem Sedimenteintrag vom Einzugsgebiet bis in den See führen und (ii) die Rekonstruktion der Hochwasserfrequenz unter veränderten Klimabedingungen. Diese Arbeit zeigt eine Untersuchung auf verschiedenen Zeitscheiben, wobei instrumentelle und historische Daten genutzt werden, um die Aufzeichnung von pre-historischen Hochwasser in den Mondseesedimenten besser zu verstehen. Innerhalb der letzten 100 Jahre wurden zwölf Abflussereignisse aufgezeichnet. Zwei Typen von detritschen Lagen können anhand von Korngröße, geochemischer Zusammensetzung und des Verteilungsmusters unterschieden werden. Detritische Lagen, welche aus siliziklastischen und dolomitischen Material bestehen, zeigen eine Sedimentherkunft vom Teileinzugsgebiet des Flysch (nördliches Einzugsgebiet) und der Nördlichen Kalkalpen (südliches Teileinzugsgebiet) auf. Diese Lagen sind im Nördlichen Becken mächtiger (0.1-3.9 mm) als im südlichen Seebecken (0.05-1.6 mm). Detritische Lagen, welche nur aus dolomitischem Material bestehen und Turbititlagen aufzeigen (0.65-32 mm), weisen auf eine Herkunft aus den Nördlichen Kalkalpen hin. Im Vergleich mit instrumentellen Zeitreihen, stammen die mächtigeren Lagen von lokalen Murereignissen im Sommer und feinere Eintragslagen von regionalen Frühjahrs- und Sommerhochwassern. Extreme Sommerhochwasser am Mondsee werden hauptsächlich durch Zyklonen vom Mittelmeer ausgelöst, z.B. Juli 1954, Juli 1997 und August 2002. Die Untersuchung des langen Sedimentkerns vom Mondsee zeigt während der letzten 2000 Jahre signifikante Hochwasserintervalle mit dekadischen Hochwasserepisoden während der Völkerwanderungszeit und im Übergang vom Mittelalter in die Kleine Eiszeit. Dies weist auf eine Verknüpfung von Abkühlungsphasen und Sommerhochwassern im Nordostalpenraum hin. Während der Mittelalterlichen Wärmephase und in der Kleinen Eiszeit kam es jedoch zu einer geringeren Hochwasseraktivität. Dies zeigt einen komplexen Zusammenhang von Temperaturentwicklung und Hochwasseraktivität in den Nordostalpen, mit einer erhöhten Zyklonenaktivät in den Übergängen von wärmeren zu kälteren Phasen. Während der letzten 7000 Jahre wurden 47 Muren und 269 Hochwasser aufgezeichnet, wobei es eine signifikante Änderung mit erhöhter Häufigkeit um 3500 und 1500 Warvenjahre v. h. gab (v.h. = vor heute = AD 1950). Diese signifikante Änderung stimmt mit einem langfristigem Abkühlungstrend überein, welcher durch alpine Gletschervorstöße und das Absinken von Baumgrenzen seit etwa 3300 Warvenjahre v.h. berichtet wird. Trotz relativ geringer Hochwasseraktivität um 1500 Warvenjahre v.h., könnte das Auftreten von Hochwasser auch das Leben Menschen in Neolithischen Pfahlbausiedlungen (5750-4750 cal. yr BP) beeinflusst haben. Während die ersten Pfahlbauten noch als Feuchtbodensiedlungen am Land entstanden, wurden spätere Siedlungen eventuell als Anpassung an stark schwankenden Seewasserspiegeln auf Pfählen im Wasser gebaut und/oder zeigen eine allgemeine Veränderung der Siedlungsaktivitäten der Neolithischen Pfahlbaukultur an, aufgrund sozio-ökonomischer Veränderungen. Ein direkter Zusammenhang zwischen dem Verlassen der Pfahlbausiedlungen und einer erhöhten Hochwasseraktivität konnte jedoch nicht festgestellt werden.
KW  - Mondsee
KW  - Paläohochwasser
KW  - Seesedimente
KW  - Warven
KW  - Klimarekonstruktion
KW  - Mondsee
KW  - Paleofloods
KW  - Lake sediments
KW  - Warves
KW  - Climate reconstruction
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-66702
ER  - 
TY  - JOUR
A1  - Weidle, Christian
A1  - Wiesenberg, Lars
A1  - El-Sharkawy, Amr
A1  - Krüger, Frank
A1  - Scharf, Andreas
A1  - Agard, Philippe
A1  - Meier, Thomas
T1  - A 3-D crustal shear wave velocity model and Moho map below the Semail Ophiolite, eastern Arabia
JF  - Geophysical journal international
N2  - The Semail Ophiolite in eastern Arabia is the largest and best-exposed slice of oceanic lithosphere on land. Detailed knowledge of the tectonic evolution of the shallow crust, in particular during and after ophiolite obduction in Late Cretaceous times is contrasted by few constraints on physical and compositional properties of the middle and lower continental crust below the obducted units. The role of inherited, pre-obduction crustal architecture remains therefore unaccounted for in our understanding of crustal evolution and the present-day geology. Based on seismological data acquired during a 27-month campaign in northern Oman, Ambient Seismic Noise Tomography and Receiver Function analysis provide for the first time a 3-D radially anisotropic shear wave velocity (V-S) model and a consistent Moho map below the iconic Semail Ophiolite. The model highlights deep crustal boundaries that segment the eastern Arabian basement in two distinct units. The previously undescribed Western Jabal Akhdar Zone separates Arabian crust with typical continental properties and a thickness of similar to 40-45 km in the northwest from a compositionally different terrane in the southeast that is interpreted as a terrane accreted during the Pan-African orogeny in Neoproterozoic times. East of the Ibra Zone, another deep crustal boundary, crustal thickness decreases to 30-35 km and very high lower crustal V-S suggest large-scale mafic intrusions into, and possible underplating of the Arabian continental crust that occurred most likely during Permian breakup of Pangea. Mafic reworking is sharply bounded by the (upper crustal) Semail Gap Fault Zone, northwest of which no such high velocities are found in the crust. Topography of the Oman Mountains is supported by a mild crustal root and Moho depth below the highest topography, the Jabal Akhdar Dome, is similar to 42 km. Radial anisotropy is robustly resolved in the upper crust and aids in discriminating dipping allochthonous units from autochthonous sedimentary rocks that are indistinguishable by isotropic V-S alone. Lateral thickness variations of the ophiolite highlight the Haylayn Ophiolite Massif on the northern flank of Jabal Akhdar Dome and the Hawasina Window as the deepest reaching unit. Ophiolite thickness is similar to 10 km in the southern and northern massifs, and <= 5 km elsewhere.
KW  - Composition and structure of the continental crust
KW  - Asia
KW  - Body waves
KW  - Seismic anisotropy
KW  - Seismic tomography
KW  - Surface waves and free oscillations
Y1  - 2022
U6  - https://doi.org/10.1093/gji/ggac223
SN  - 0956-540X
SN  - 1365-246X
VL  - 231
IS  - 2
SP  - 817
EP  - 834
PB  - Oxford University Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Freybourger, Marion
A1  - Krüger, Frank
A1  - Achauer, Ulrich
T1  - A 22 degree long seismic profile for the study of the top D"
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Balagansky, V. V.
A1  - Timmerman, Martin Jan
A1  - Kozlova, N. Ye.
A1  - Kisilitsyn, R. V.
T1  - A 2.44 Ga old mafic dyke swarm in the Kolvitsa Belt, Kola Peninsula, Russia: implications for the early Palaeoproterozoic tectonics in the north-eastern Fennoscandian Shield
Y1  - 2001
ER  - 
TY  - JOUR
A1  - Wichura, Henry
A1  - Jacobs, Louis L.
A1  - Lin, Andrew
A1  - Polcyn, Michael J.
A1  - Manthi, Fredrick K.
A1  - Winkler, Dale A.
A1  - Strecker, Manfred
A1  - Clemens, Matthew
T1  - A 17-My-old whale constrains onset of uplift and climate change in east Africa
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - Timing and magnitude of surface uplift are key to understanding the impact of crustal deformation and topographic growth on atmospheric circulation, environmental conditions, and surface processes. Uplift of the East African Plateau is linked to mantle processes, but paleoaltimetry data are too scarce to constrain plateau evolution and subsequent vertical motions associated with rifting. Here, we assess the paleotopographic implications of a beaked whale fossil (Ziphiidae) from the Turkana region of Kenya found 740 km inland from the present-day coastline of the Indian Ocean at an elevation of 620 m. The specimen is similar to 17 My old and represents the oldest derived beaked whale known, consistent with molecular estimates of the emergence of modern straptoothed whales (Mesoplodon). The whale traveled from the Indian Ocean inland along an eastward-directed drainage system controlled by the Cretaceous Anza Graben and was stranded slightly above sea level. Surface uplift from near sea level coincides with paleoclimatic change from a humid environment to highly variable and much drier conditions, which altered biotic communities and drove evolution in east Africa, including that of primates.
KW  - east Africa
KW  - Ziphiidae
KW  - uplift
KW  - drainage
KW  - paleoenvironment
Y1  - 2015
U6  - https://doi.org/10.1073/pnas.1421502112
SN  - 0027-8424
VL  - 112
IS  - 13
SP  - 3910
EP  - 3915
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Zhang, Yang
A1  - Huang, Wentao
A1  - Huang, Baochun
A1  - van Hinsbergen, Douwe J. J.
A1  - Yang, Tao
A1  - Dupont-Nivet, Guillaume
A1  - Guo, Zhaojie
T1  - 53-43Ma Deformation of Eastern Tibet Revealed by Three Stages of Tectonic Rotation in the Gongjue Basin
JF  - Journal of geophysical research : Solid earth
N2  - The Gongjue basin from the eastern Qiangtang terrane is located in the transition region where the regional structural lineation curves from east-west-oriented in Tibet to north-south-oriented in Yunnan. In this study, we sampled the red beds in the basin from the lower Gongjue to upper Ranmugou formations for the first time covering the entire stratigraphic profile. The stratigraphic ages are bracketed within 53-43Ma by new detrital zircon U-Pb ages constraining the maximum deposition age to 52.51.5Ma. Rock magnetic and petrographic studies indicate that detrital magnetite and hematite are the magnetic carriers. Positive reversals and fold tests demonstrate that the characteristic remanent magnetization has a primary origin. The Gongjue and Ranmugou formations yield mean characteristic remanent magnetization directions of D-s/I-s=31.0 degrees/21.3 degrees and D-s/I-s=15.9 degrees/22.0 degrees, respectively. The magnetic inclination of these characteristic remanent magnetizations is significantly shallowed compared to the expected inclination for the locality. However, the elongation/inclination correction method does not provide a meaningful correction, likely because of syn-depositional rotation. Rotations relative to the Eurasian apparent polar wander path occurred in three stages: Stage I, 33.33.4 degrees clockwise rotation during the deposition of the Gongjue and lower Ranmugou formations; Stage II, 26.93.7 degrees counterclockwise rotation during deposition of the lower and middle Ranmugou formation; and Stage III, 17.73.3 degrees clockwise rotation after 43Ma. The complex rotation history recorded in the basin is possibly linked to sinistral shear along the Qiangtang block during India indentation into Asia and the early stage of the extrusion of the northwestern Indochina blocks away from eastern Tibet.
KW  - eastern Qiangtang terrane
KW  - Gongjue basin
KW  - paleomagnetism
KW  - inclination shallowing
KW  - rotation
Y1  - 2018
U6  - https://doi.org/10.1002/2018JB015443
SN  - 2169-9313
SN  - 2169-9356
VL  - 123
IS  - 5
SP  - 3320
EP  - 3338
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - van Schaik, N. Loes M. B.
A1  - Tronicke, Jens
T1  - 4D ground-penetrating radar during a plot scale dye tracer experiment
JF  - Journal of applied geophysics
N2  - Flow phenomena in the unsaturated zone are highly variable in time and space. Thus, it is challenging to measure and monitor such processes under field conditions. Here, we present a new setup and interpretation approach for combining a dye tracer experiment with a 4D ground-penetrating radar (GPR) survey. Therefore, we designed a rainfall experiment during which we measured three surface-based 3D GPR surveys using a pair of 500 MHz antennas. Such a survey setup requires accurate acquisition and processing techniquesto extract time-lapse information supporting the interpretation of selected cross-sections photographed after excavating the site. Our results reveal patterns of traveltime changes in the measured GPR data, which are associated with soil moisture changes. As distinct horizons are present at our site, such changes can be quantified and transferred into changes in total soil moisture content. Our soil moisture estimates are similar to the amount of infiltrated water, which confirms our experimental approach and makes us confident for further developing this strategy, especially, with respect to improving the temporal and spatial resolution. (C) 2015 Elsevier B.V. All rights reserved.
KW  - Ground penetrating radar
KW  - Time-lapse imaging
KW  - Brilliant blue
Y1  - 2015
U6  - https://doi.org/10.1016/j.jappgeo.2015.04.016
SN  - 0926-9851
SN  - 1879-1859
VL  - 118
SP  - 139
EP  - 144
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Krmíček, Lukáš
A1  - Timmerman, Martin Jan
A1  - Ziemann, Martin Andreas
A1  - Sudo, Masafumi
A1  - Ulrych, Jaromir
T1  - 40Ar/39Ar step-heating dating of phlogopite and kaersutite megacrysts from the Železná hůrka (Eisenbühl) Pleistocene scoria cone, Czech Republic
JF  - Geologica Carpathica
N2  - (40)A/Ar-39 step-heating of mica and amphibole megacrysts from hauyne-bearing olivine melilitite scoria/tephra from the Zelezna hurka yielded a 435 +/- 108 ka isotope correlation age for phlogopite and a more imprecise 1.55 Ma total gas age of the kaersutite megacryst. The amphibole megacrysts may constitute the first, and the younger phlogopite megacrysts the later phase of mafic, hydrous melilitic magma crystallization. It cannot be ruled out that the amphibole megacrysts are petrogenetically unrelated to tephra and phlogopite megacrysts and were derived from mantle xenoliths or disaggregated older, deep crustal pegmatites. This is in line both with the rarity of amphibole at Zelezna hurka and with the observed signs of magmatic resorption at the edges of amphibole crystals.
KW  - Bohemian Massif
KW  - Zelezna hurka
KW  - Eisenbuhl
KW  - argon dating
KW  - mica
KW  - amphibole
KW  - melilitite
Y1  - 2020
U6  - https://doi.org/10.31577/GeolCarp.71.4.6
SN  - 1335-0552
SN  - 1336-8052
VL  - 71
IS  - 4
SP  - 382
EP  - 387
PB  - Veda
CY  - Bratislava
ER  - 
TY  - THES
A1  - Engelhardt, Jonathan
T1  - 40Ar/39Ar geochronology of ICDP PALEOVAN drilling cores
T1  - 40Ar/39Ar Geochronologie der ICDP PALEOVAN Bohrkerne
N2  - The scientific drilling campaign PALEOVAN was conducted in the summer of 2010 and was part of the international continental drilling programme (ICDP). The main goal of the campaign was the recovery of a sensitive climate archive in the East of Anatolia. Lacustrine deposits underneath the lake floor of ‘Lake Van’ constitute this archive. The drilled core material was recovered from two locations: the Ahlat Ridge and the Northern Basin. A composite core was constructed from cored material of seven parallel boreholes at the Ahlat Ridge and covers an almost complete lacustrine history of Lake Van. The composite record offered sensitive climate proxies such as variations of total organic carbon, K/Ca ratios, or a relative abundance of arboreal pollen. These proxies revealed patterns that are similar to climate proxy variations from Greenland ice cores. Climate variations in Greenland ice cores have been dated by modelling the timing of orbital forces to affect the climate. Volatiles from melted ice aliquots are often taken as high-resolution proxies and provide a base for fitting the according temporal models.
The ICDP PALEOVAN scientific team fitted proxy data from the lacustrine drilling record to ice core data and constructed an age model. Embedded volcaniclastic layers had to be dated radiometrically in order to provide independent age constraints to the climate-stratigraphic age model. Solving this task by an application of the 40Ar/39Ar method was the main objective of this thesis. Earlier efforts to apply the 40Ar/39Ar dating resulted in inaccuracies that could not be explained satisfactorily.
The absence of K-rich feldspars in suitable tephra layers implied that feldspar crystals needed to be 500 μm in size minimum, in order to apply single-crystal 40Ar/39Ar dating. Some of the samples did not contain any of these grain sizes or only very few crystals of that size. In order to overcome this problem this study applied a combined single-crystal and multi-crystal approach with different crystal fractions from the same sample. The preferred method of a stepwise heating analysis of an aliquot of feldspar crystals has been applied to three samples. The Na-rich crystals and their young geological age required 20 mg of inclusion-free, non-corroded feldspars. Small sample volumes (usually 25 % aliquots of 5 cm3 of sample material – a spoon full of tephra) and the widespread presence of melt-inclusion led to the application of combined single- and multigrain total fusion analyses. 40Ar/39Ar  analyses on single crystals have the advantage of being able to monitor the presence of excess 40Ar and detrital or xenocrystic contamination in the samples. Multigrain analyses may hide the effects from these obstacles. The results from the multigrain analyses are therefore discussed with respect to the findings from the respective cogenetic single crystal ages. Some of the samples in this study were dated by 40Ar/39Ar on feldspars on multigrain separates and (if available) in combination with only a few single crystals. 40Ar/39Ar ages from two of the samples deviated statistically from the age model. All other samples resulted in identical ages. The deviations displayed older ages than those obtained from the age model. t-Tests compared radiometric ages with available age control points from various proxies and from the relative paleointensity of the earth magnetic field within a stratigraphic range of ± 10 m. Concordant age control points from different relative chronometers indicated that deviations are a result of erroneous 40Ar/39Ar ages. The thesis argues two potential reasons for these ages: (1) the irregular appearance of 40Ar from rare melt- and fluid- inclusions and (2) the contamination of the samples with older crystals due to a rapid combination of assimilation and ejection. 
Another aliquot of feldspar crystals that underwent separation for the application of 40Ar/39Ar dating was investigated for geochemical inhomogeneities. Magmatic zoning is ubiquitous in the volcaniclastic feldspar crystals. Four different types of magmatic zoning were detected. The zoning types are compositional zoning (C-type zoning), pseudo-oscillatory zoning of trace ele- ment concentrations (PO-type zoning), chaotic and patchy zoning of major and trace element concentrations (R-type zoning) and concentric zoning of trace elements (CC-type zoning). Sam- ples that deviated in 40Ar/39Ar  ages showed C-type zoning, R-type zoning or a mix of different types of zoning (C-type and PO-type). Feldspars showing PO-type zoning typically represent the smallest grain size fractions in the samples. The constant major element compositions of these crystals are interpreted to represent the latest stages in the compositional evolution of feldspars in a peralkaline melt. PO-type crystals contain less melt- inclusions than other zoning types and are rarely corroded. This thesis concludes that feldspars that show PO-type zoning are most promising chronometers for the 40Ar/39Ar method, if samples provide mixed zoning types of Quaternary anorthoclase feldspars.
Five samples were dated by applying the 40Ar/39Ar method to volcanic glass. High fractions of atmospheric Ar (typically > 98%) significantly hampered the precision of the 40Ar/39Ar ages and resulted in rough age estimates that widely overlap the age model. Ar isotopes indicated that the glasses bore a chorine-rich Ar-end member. The chlorine-derived 38Ar indicated chlorine-rich fluid-inclusions or the hydration of the volcanic glass shards. This indication strengthened the evidence that irregularly distributed melt-inclusions and thus irregular distributed excess 40Ar influenced the problematic feldspar 40Ar/39Ar ages. Whether a connection between a corrected initial 40Ar/36Ar ratio from glasses to the 40Ar/36Ar ratios from pore waters exists remains unclear.
This thesis offers another age model, which is similarly based on the interpolation of the temporal tie points from geophysical and climate-stratigraphic data. The model used a PCHIP- interpolation (piecewise cubic hermite interpolating polynomial) whereas the older age model used a spline-interpolation. Samples that match in ages from 40Ar/39Ar dating of feldspars with the earlier published age model were additionally assigned with an age from the PCHIP- interpolation. These modelled ages allowed a recalculation of the Alder Creek sanidine mineral standard. The climate-stratigraphic calibration of an 40Ar/39Ar mineral standard proved that the age versus depth interpolations from PAELOVAN drilling cores were accurate, and that the applied chronometers recorded the temporal evolution of Lake Van synchronously.
Petrochemical discrimination of the sampled volcaniclastic material is also given in this thesis. 41 from 57 sampled volcaniclastic layers indicate Nemrut as their provenance. Criteria that served for the provenance assignment are provided and reviewed critically. Detailed correlations of selected PALEOVAN volcaniclastics to onshore samples that were described in detail by earlier studies are also discussed. The sampled volcaniclastics dominantly have a thickness of < 40 cm and have been ejected by small to medium sized eruptions. Onshore deposits from these types of eruptions are potentially eroded due to predominant strong winds on Nemrut and Süphan slopes. An exact correlation with the data presented here is therefore equivocal or not possible at all.
Deviating feldspar 40Ar/39Ar ages can possibly be explained by inherited 40Ar from feldspar xenocrysts contaminating the samples. In order to test this hypothesis diffusion couples of Ba were investigated in compositionally zoned feldspar crystals. The diffusive behaviour of Ba in feldspar is known, and gradients in the changing concentrations allowed for the calculation of the duration of the crystal’s magmatic development since the formation of the zoning interface. Durations were compared with degassing scenarios that model the Ar-loss during assimilation and subsequent ejection of the xenocrystals. Diffusive equilibration of the contrasting Ba concentrations is assumed to generate maximum durations as the gradient could have been developed in several growth and heating stages. The modelling does not show any indication of an involvement of inherited 40Ar in any of the deviating samples. However, the analytical set-up represents the lower limit of the required spatial resolution. Therefore, it cannot be excluded that the degassing modelling relies on a significant overestimation of the maximum duration of the magmatic history. Nevertheless, the modelling of xenocrystal degassing evidences that the irregular incorporation of excess 40Ar by melt- and fluid inclusions represents the most critical problem that needs to be overcome in dating volcaniclastic feldspars from the PALEOVAN drill cores. This thesis provides the complete background in generating and presenting 40Ar/39Ar ages that are compared to age data from a climate-stratigraphic model. Deviations are identified statistically and then discussed in order to find explanations from the age model and/or from 40Ar/39Ar geochronology. Most of the PALEOVAN stratigraphy provides several chronometers that have been proven for their synchronicity. Lacustrine deposits from Lake Van represent a key archive for reconstructing climate evolution in the eastern Mediterranean and in the Near East. The PALEOVAN record offers a climate-stratigraphic age model with a remarkable accuracy and resolution.
N2  - Die PALEOVAN−Bohrkampagne des internationalen kontinentalen Bohrprogramms ICDP wurde im Sommer 2010 realisiert. Das übergeordnete Ziel dieser Kampagne war die Entnahme eines Klimaarchivs im Osten Anatoliens. Als Archiv dienen Süßwasserablagerungen am Grund des Vansees. PALEOVAN Bohrkerne bieten lakustrine Ablagerungen von zwei Lokalitäten des Sees, und zwar der Ahlat Ridge und des Northern Basins. Durch das Zusammenstellen bestmöglicher Bohrkernbestände aus sieben parallelen Bohrungen auf der Ahlat Ridge, konnte die nahezu vollständige Aufzeichnung der Geschichte des Sees gewonnen werden. Dieses detaillierte Archiv zeichnete sensible Klimafaktoren auf. Als Beispiele sind zu nennen: die Variationen organischen Kohlenstoffs, das Verhältnis von Kalium zu Kalzium und die Anteile arborealer Pollen gegenüber dem Gesamtpollenbestand. Stellvertreterdaten für Klimavariationen (sogenannte Proxies) ähneln in ihrem Muster sehr stark den bekannten Klimavariationen aus Eisbohrkernen des Grönlandeises. Da das Timing der Klimavariationen in den Grönlandeiskernen durch Datierungen mithilfe im Eis gespeicherter Gasphasen und orbitaler Modellberechnungen sehr genau bekannt ist, konnten Sedimentolog*innen des PALEOVAN−Teams ein klimastratigraphisches Altersmodell aus den Proxies berechnen. Die Kernaufgabe der hier vorgelegten Dissertation ist es, eingelagerte pyroklastische Ablagerungen mithilfe der 40Ar/39Ar−Methode zu datieren und das Altersmodell zu diskutieren. Die Notwendigkeit der 40Ar/39Ar−Datierungen war besonders gegeben, da vorab publizierte radiometrische Datierungen von ICDP−PALEOVAN Bohrkernen statistisch nicht ausreichend beschrieben wurden und vorhandene Abweichungen gegenüber dem Altersmodell undiskutiert blieben.
An der westlichen und nördlichen Küste des Sees befinden sich zwei Stratovulkane: Nemrut und Süphan. Beide Vulkane haben über die Dauer der kompletten Seegeschichte pyroklastisches Material im See abgelagert. Feldspäte und vulkanische Gläser aus rhyolitischen und trachytischen Auswurfprodukten wurden auf ihre Zusammensetzung untersucht und es wurde ihre Eignung für eine Anwendung der 40Ar/39Ar−Geochronologie festgestellt. Die Abwesenheit hoher Kaliumkonzentrationen in Feldspäten aus geeigneten pyroklastischen Lagen bedeutet, dass Kristalle eine Mindestgröße von ca. 500 Mikrometer benötigen, um Analysen an einzelnen Kristallen durchführen zu können. Nicht alle Proben liefern ausreichend Kristalle dieser groben Korngröße. Somit wurde eine Methode gewählt, die Mehrkorn und Einzelkornanalysen miteinander kombiniert. Die bevorzugte Methode des schrittweisen Ausheizens war nur mit drei Proben möglich. Grund dafür ist, dass der geringe Kaliumgehalt und das junge geologische Alter große Mengen (ca. 20 mg) einschluss− und korrosionsfreier Feldspäte benötigten. Die geringen Probenmengen (25% Aliquot von üblicherweise 5 cm3 Probenmaterial) und die Omnipräsenz von Schmelzeinschlüssen in den Feldspäten legten nahe, auf die Methodik des schlagartigen Ausheizens von Einzel− und Mehrkornproben zu setzen. 40Ar/39Ar−Datierungen an einzelnen Feldspäten haben den Vorteil, dass sich ein vorhandener Überschuss von 40Ar oder Kontaminationen detritischer Körner leicht feststellen lassen und in der Altersberechnung berücksichtigt werden können. Mehrkornanalysen zeigen diese Hürden nur bei intensiver Kontamination und bergen die Gefahr, radiometrische Alter zu bestimmen, die von dem tatsächlichen geologischen Alter abweichen, weil sie zu alt sind. 40Ar/39Ar−Datierungen in dieser Dissertation wurden deshalb für die meisten Proben mithilfe von Mehrkornanalysen und (wenn vorhanden) in Kombination mit wenigen Einzelkornanalysen durchgeführt.
Bis auf die Resultate zweier Proben sind die radiometrischen Alter der Feldspäte statistisch gesehen identisch zu den Altersabschätzungen des klimastratigraphischen Altersmodells. Abweichungen zeigen ausschließlich ältere radiometrische Alter einzelner Kornfraktionen. Die beiden abweichenden Proben sind ebenfalls älter als das Altersmodell. Eine statistische Auswertung mittels t−Tests beweist die Abweichungen der radiometrischen von den klimastratigraphischen Altersdaten. Das Altersmodell wurde mit jedem der radiometrischen Alter innerhalb eines stratigraphischen Einzugsbereichs von ± 10 Metern verglichen. Die Konkordanz der Altershinweise aus unterschiedlichen Klimaproxies und aus geophysikalischen Altershinweisen (durch das Identifizieren zeitlich bekannter Variationen des Erdmagnetfelds) legen nahe, dass beiden Abweichungen fehlerhafte 40 Ar/39 Ar−Datierungen zugrunde liegen. Zwei mögliche Ursachen werden in Betracht gezogen: (1) unregelmäßiges beziehungsweise vereinzeltes Auftreten von überschüssigem 40Ar im Zusammenhang mit Schmelz− und Fluideinschlüssen oder (2) Kontamination der Probe mit älteren, xenokristischen Feldspäten durch eine zügige (im Zeitraum von Tagen) Kombination von magmatischer Assimilation und Auswurf des Materials. Ebenfalls nicht auszuschließen ist eine detritische Kontamination. Die normalverteilten 40Ar/39Ar−Werte der Proben sind allerdings untypisch für eine detritische Kontamination.
Je ein Aliquot der selektierten Kristallfraktionen wurde intensiv auf vorhandene Zonierungen untersucht. Alle untersuchten Feldspatproben zeigen Elementzonierungen, die sich einteilen lassen. Die Zonierungen sind entweder kompositionelle Zonierungen der Hauptzusammensetzung („C-type – compositional type“), pseudo-oszillatorische Zonierungen gewisser Spurenelementkonzentrationen („PO-type“), konzentrische Zonierungen von Spurenelementkonzentrationen („CC-type – concentric type“) und chaotisch-fleckige Zonierungsmuster („R-type – resorbed and patchy“). Proben, deren 40Ar/39Ar−Alter abweichen, zeigen Zonierungen in ihrer Hauptzusammensetzung (C-type), fleckige Zonierungen (R-type) oder zeigen eine Mischung aus unterschiedlichen Zonierungstypen (C-type und PO-type). Feldspäte, die ausschließlich eine Zonierung ihrer Spurenelmente (PO-type) zeigen, liegen typischerweise in kleineren Korngrößen vor und markieren Zusammensetzungen, die typisch sind für die spätesten Phasen der magmatischen Entwicklung von Feldspäten in peralkalinen Gesteinen. Diese Kristalle sind in der Regel arm an Schmelzeinschlüssen und nur selten korrodiert. Die vorliegende Arbeit weist Feldspäte, die keine Zonierung in ihrer Hauptzusammensetzung, sondern nur pseudo-oszillatorische Spurenelementvariationen aufzeigen, als ideale Chronometer für die Anwendung der 40Ar/39Ar−Methode an Quartären, kaliumarmen Feldspäten aus.
Um Abweichende Proben erneut zu analysieren und um stratigraphische Abschnitte zu datieren, die nicht erfolgreich beprobt werden konnten, wurden fünf Proben datiert, indem die 40Ar/39Ar−Methode auf vulkanisches Glas angewendet wurde. Hohe Gehalte an atmosphärischem Argon (in der Regel > 98 %) führten allerdings zu ungenauen radiometrischen Altersbestimmungen, die aufgrund ihrer großen Fehler keine Abweichungen vom Altersmodell zeigen. Die Gläser zeigen Hinweise darauf, dass Variationen in den Altern der Feldspäte auf die Gegenwart eines Ar-Reservoirs in Schmelzeinschlüssen zurückzuführen sein könnte, das weder radiogen noch atmosphärisch ist. Ob eine Verknüpfung der Ar-Isotopien in vulkanischen Gläsern und in Porenwässern gegeben ist, bleibt offen. Instrumentelle und methodische Hürden lassen nur eine Vermutung zu, dass Porenwässer und vulkanische Gläser in ihren Ar-Isotopendaten eine Verknüpfung zeigen könnten.
Ein neues Alterstiefenmodell, das ebenfalls auf der Interpolation von Altershinweisen durch Klimaproxies und geophysikalischer Daten basiert wird in dieser Arbeit ebenfalls vorgelegt. Im Gegensatz zu bestehenden „Spline“-Interpolationen wurde in dieser Dissertation eine PCHIP- Interpolation bevorzugt. Abgesehen von abweichenden Proben wurden allen Proben, die mithilfe der 40Ar/39Ar−Methode an Feldspäten datiert sind, zusätzlich ein klimastratigraphisches Modellalter zugewiesen. Diese Modellalter bieten die Grundlage dafür, das Alter des in der Datierung benutzten Mineralstandards (Alder Creek Sanidine) nachrechnen zu können. Die erfolgreiche klimastratigraphische Kalibrierung des Standards beweist, dass Alterstiefenmodelle aus den PALEOVAN-Bohrkernen genau sind, und dass alle verwendeten Chronometer innerhalb der angezeigten Varianzen ein synchrones Timing zulassen.
Die Dissertation bietet petrochemische Charakterisierungen der entnommenen Proben an und diskutiert nachvollziehbar mögliche Provenanzen der Pyroklastite. 41 von 57 entnommenen Proben lassen sich Nemrut zuordnen. Kriterien, die für eine Zuordnung herangezogen wurden, werden aufgezeigt und diskutiert. Eine mögliche Korrelation der datierten Proben zu pyroklastischen Einheiten, die in der Literatur an den Hängen der Stratovulkane im Detail beschrieben wurden, wird ebenfalls diskutiert. Die beprobten pyroklasitischen Lagen haben geringe Mächtigkeiten (in der Regel < 40 cm) und liegen mittleren bis kleineren Eruptionen zugrunde. Diese Eruptionen hinterlassen keine oder nur schwer definierbare pyroklastische Einheiten von geringer Mächtigkeit an Land. Eine genaue Korrelation ist mit den hier präsentierten Daten deshalb nicht oder nur sehr vage möglich.
Abweichende radiometrische Alter aus Datierungen von Feldspat könnten im Zusammenhang mit vererbtem 40Ar aus Xenokristallen stehen. Um diese Hypothese zu testen, wurden diffusionsabhängige Konzentrationsschwankungen von Barium in zonierten Feldspäten untersucht. Da das diffusive Verhalten von Barium in Feldspat bekannt ist, kann durch die Analyse des Konzentrationsgradienten die Dauer der magmatischen Entwicklung ab der Bildung der untersuchten Zonierung berechnet werden. Diese Zeitspanne wurde genutzt, um zu modellieren, ob Xenokristalle während einer unvollständigen Assimilation komplett entgast werden. Dafür wurde angenommen, dass das diffusive Angleichen von unterschiedlichen Bariumkonzentrationen maximale Werte für die Dauer von der Assimilation bis zum Auswurf liefert. Die Modellierung zeigt, dass vererbtes 40Ar aus Xenokristallen keinen Anteil an den abweichenden Altern haben. Allerdings sind die erhobenen Diffusionsgradienten am Rande der benötigten analytischen Auflösung, und eine Überschätzung der Dauer der magmatischen Prozesse kann nicht ausgeschlossen werden. Die Diffusionsprofile sind ein weiterer Hinweis dafür, dass unregelmäßige beziehungsweise vereinzelte Quellen von überschüssigem 40Ar die schwierigste Hürde für 40Ar/39Ar−Datierungen an ICDP-PALEOVAN Bohrkernen darstellen.
Die vorgelegte Arbeit bietet nicht nur 40Ar/39Ar−Datierungen, um das vorhandene Altersmodell kritisch zu diskutieren, sondern zeigt, wie Abweichungen statistisch zu erfassen sind, welche mineralogischen Beobachtungen in die Interpretation abweichender radiometrischer Alter miteinbezogen werden sollten und wie die Synchronizität verschiedener Chronometer getestet werden kann. Die Korrektheit des klima-stratigraphischen Timings der PALEOVAN Kerne ist mit dieser Arbeit nachgewiesen. Vergleiche der Proxydaten zu anderen Klimaarchiven deren Auflösung sogar höher als die der Milankovitchzyklen ist (die Auflösung der Dnsgaard-Oeschger Ereignisse), existieren für viele Kerne des PALEOVAN-Archivs. Die Kerne aus dem PALEOVAN Projekt repräsentieren damit ein Schlüsselarchiv für die Rekonstruktion des Klimas im Nahen Osten. Dieses Archiv bietet ein klima-stratigraphisches Altersmodell von bemerkenswerter Genauigkeit und Auflösung.
KW  - Lake Van
KW  - feldspar
KW  - lacustrine record
KW  - volcaniclastics
KW  - 40Ar/39Ar
KW  - Vansee
KW  - Feldspat
KW  - lakustrine Abfolge
KW  - Vulkaniklastika
KW  - 40Ar/39Ar
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-429539
ER  - 
TY  - JOUR
A1  - Franz, Gerhard
A1  - Sudo, Masafumi
A1  - Khomenko, Vladimir
T1  - 40Ar/39Ar dating of a hydrothermal pegmatitic buddingtonite–muscovite assemblage from Volyn, Ukraine
JF  - European journal of mineralogy : EJM : an international journal on mineralogy, petrology, geochemistry, and related sciences
N2  - We determined Ar-40/Ar-39 ages of buddingtonite, occurring together with muscovite, with the laser-ablation method. This is the first attempt to date the NH4-feldspar buddingtonite, which is typical for sedimentary-diagenetic environments of sediments, rich in organic matter, or in hydrothermal environments, associated with volcanic geyser systems. The sample is a hydrothermal breccia, coming from the Paleoproterozoic pegmatite field of the Korosten Plutonic Complex, Volyn, Ukraine. A detailed characterization by optical methods, electron microprobe analyses, backscattered electron imaging, and IR analyses showed that the buddingtonite consists of euhedral-appearing platy crystals of tens of micrometers wide, 100 or more micrometers in length, which consist of fine-grained fibers of <= 1 mu m thickness. The crystals are sector and growth zoned in terms of K-NH4-H3O content. The content of K allows for an age determination with the Ar-40/Ar-39 method, as well as in the accompanying muscovite, intimately intergrown with the buddingtonite. The determinations on muscovite yielded an age of 1491 +/- 9 Ma, interpreted as the hydrothermal event forming the breccia. However, buddingtonite apparent ages yielded a range of 563 +/- 14 Ma down to 383 +/- 12 Ma, which are interpreted as reset ages due to Ar loss of the fibrous buddingtonite crystals during later heating. We conclude that buddingtonite is suited for Ar-40/Ar-39 age determinations as a supplementary method, together with other methods and minerals; however, it requires a detailed mineralogical characterization, and the ages will likely represent minimum ages.
Y1  - 2022
U6  - https://doi.org/10.5194/ejm-34-7-2022
SN  - 0935-1221
SN  - 1617-4011
VL  - 34
IS  - 1
SP  - 7
EP  - 18
PB  - Copernicus
CY  - Göttingen
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  - Platz, Anna
A1  - Weckmann, Ute
A1  - Pek, Josef
A1  - Kovacikova, Svetlana
A1  - Klanica, Radek
A1  - Mair, Johannes
A1  - Aleid, Basel
T1  - 3D imaging of the subsurface electrical resistivity structure in West Bohemia/Upper Palatinate covering mofettes and quaternary volcanic structures by using magnetotellurics
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - The region of West Bohemia and Upper Palatinate belongs to the West Bohemian Massif. The study area is situated at the junction of three different Variscan tectonic units and hosts the ENE-WSW trending Ohre Rift as well as many different fault systems. The entire region is characterized by ongoing magmatic processes in the intra-continental lithospheric mantle expressed by a series of phenomena, including e.g. the occurrence of repeated earthquake swarms and massive degassing of mantle derived CO2 in form of mineral springs and mofettes. Ongoing active tectonics is mainly manifested by Cenozoic volcanism represented by different Quaternary volcanic structures. All these phenomena make the Ohre Rift a unique target area for European intra-continental geo-scientific research. With magnetotelluric (MT) measurements we image the subsurface distribution of the electrical resistivity and map possible fluid pathways. Two-dimensional (2D) inversion results by Munoz et al. (2018) reveal a conductive channel in the vicinity of the earthquake swarm region that extends from the lower crust to the surface forming a pathway for fluids into the region of the mofettes. A second conductive channel is present in the south of their model; however, their 2D inversions allow ambiguous interpretations of this feature. Therefore, we conducted a large 3D MT field experiment extending the study area towards the south. The 3D inversion result matches well with the known geology imaging different fluid/magma reservoirs at crust-mantle depth and mapping possible fluid pathways from the reservoirs to the surface feeding known mofettes and spas. A comparison of 3D and 2D inversion results suggests that the 2D inversion results are considerably characterized by 3D and off-profile structures. In this context, the new results advocate for the swarm earthquakes being located in the resistive host rock surrounding the conductive channels; a finding in line with observations e.g. at the San Andreas Fault, California.
KW  - Magnetotellurics
KW  - Ohre Rift
KW  - Conductive channel
KW  - Fluid/magma reservoir
KW  - Earthquake swarm
Y1  - 2022
U6  - https://doi.org/10.1016/j.tecto.2022.229353
SN  - 0040-1951
SN  - 1879-3266
VL  - 833
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Schennen, Stephan
A1  - Tronicke, Jens
A1  - Wetterich, Sebastian
A1  - Allroggen, Niklas
A1  - Schwamborn, Georg
A1  - Schirrmeister, Lutz
T1  - 3D ground-penetrating radar imaging of ice complex deposits in northern East Siberia
JF  - Geophysics
N2  - Ice complex deposits are characteristic, ice-rich formations in northern East Siberia and represent an important part in the arctic carbon pool. Recently, these late Quaternary deposits are the objective of numerous investigations typically relying on outcrop and borehole data. Many of these studies can benefit from a 3D structural model of the subsurface for upscaling their observations or for constraining estimations of inventories, such as the local carbon stock. We have addressed this problem of structural imaging by 3D ground-penetrating radar (GPR), which, in permafrost studies, has been primarily used for 2D profiling. We have used a 3D kinematic GPR surveying strategy at a field site located in the New Siberian Archipelago on top of an ice complex. After applying a 3D GPR processing sequence, we were able to trace two horizons at depths below 20 m. Taking available borehole and outcrop data into account, we have interpreted these two features as interfaces of major lithologic units and derived a 3D cryostratigraphic model of the subsurface. Our data example demonstrated that a 3D surveying and processing strategy was crucial at our field site and showed the potential of 3D GPR to image geologic structures in complex ice-rich permafrost landscapes.
Y1  - 2016
U6  - https://doi.org/10.1190/GEO2015-0129.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 81
SP  - WA195
EP  - WA202
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Koyan, Philipp
A1  - Tronicke, Jens
A1  - Allroggen, Niklas
T1  - 3D ground-penetrating radar attributes to generate classified facies models
BT  - a case study from a dune island
JF  - Geophysics
N2  - Ground-penetrating radar (GPR) is a standard geophysical technique used to image near-surface structures in sedimentary environments. In such environments, GPR data acquisition and processing are increasingly following 3D strategies. However, the processed GPR data volumes are typically still interpreted using selected 2D slices and manual concepts such as GPR facies analyses. In seismic volume interpretation, the application of (semi-)automated and reproducible approaches such as 3D attribute analyses as well as the production of attribute-based facies models are common practices today. In contrast, the field of 3D GPR attribute analyses and corresponding facies models is largely untapped. We have developed and applied a workflow to produce 3D attribute-based GPR facies models comprising the dominant sedimentary reflection patterns in a GPR volume, which images complex sandy structures on the dune island of Spiekeroog (Northern Germany). After presenting our field site and details regarding our data acquisition and processing, we calculate and filter 3D texture attributes to generate a database comprising the dominant texture features of our GPR data. Then, we perform a dimensionality reduction of this database to obtain meta texture attributes, which we analyze and integrate using composite imaging and (also considering additional geometric information) fuzzy c-means cluster analysis resulting in a classified GPR facies model. Considering our facies model and a corresponding GPR facies chart, we interpret our GPR data set in terms of near-surface sedimentary units, the corresponding depositional environments, and the recent formation history at our field site. Thus, we demonstrate the potential of our workflow, which represents a novel and clear strategy to perform a more objective and consistent interpretation of 3D GPR data collected across different sedimentary environments.
KW  - ground-penetrating radar
KW  - attributes
KW  - interpretation
KW  - sedimentology
Y1  - 2021
U6  - https://doi.org/10.1190/GEO2021-0204.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 86
IS  - 6
SP  - B335
EP  - B347
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - Heincke, Bjorn H.
A1  - Koyan, Philipp
A1  - Wheeler, Walter
A1  - Ronning, Jan S.
T1  - 3D ground-penetrating radar attribute classification
BT  - a case study from a paleokarst breccia pipe in the Billefjorden area on Spitsbergen, Svalbard
JF  - Geophysics
N2  - Ground-penetrating radar (GPR) is a method that can provide detailed information about the near subsurface in sedimentary and carbonate environments. 
The classical interpretation of GPR data (e.g., based on manual feature selection) often is labor-intensive and limited by the experience of the intercally used for seismic interpretation, can provide faster, more repeatable, and less biased interpretations. We have recorded a 3D GPD data set collected across a paleokarst breccia pipe in the Billefjorden area on Spitsbergen, Svalbard. After performing advanced processing, we compare the results of a classical GPR interpretation to the results of an attribute-based classification. 

Our attribute classification incorporates a selection of dip and textural attributes as the input for a k-means clustering approach. Similar to the results of the classical interpretation, the resulting classes differentiate between undisturbed strata and breccias or fault zones. 
The classes also reveal details inside the breccia pipe that are not discerned in the classical fer that the intrapipe GPR facies result from subtle differences, such as breccia lithology, clast size, or pore-space filling.
Y1  - 2022
U6  - https://doi.org/10.1190/GEO2021-0651.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 87
IS  - 4
SP  - WB19
EP  - WB30
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Ibarra, Federico
A1  - Liu, Sibiao
A1  - Meeßen, Christian
A1  - Prezzi, Claudia Beatriz
A1  - Bott, Judith
A1  - Scheck-Wenderoth, Magdalena
A1  - Sobolev, Stephan Vladimir
A1  - Strecker, Manfred
T1  - 3D data-derived lithospheric structure of the Central Andes and its implications for deformation: Insights from gravity and geodynamic modelling
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - We present a new three-dimensional density model of the Central Andes characterizing the structure and composition of the lithosphere together with a geodynamic simulation subjected to continental intraplate shortening. The principal aim of this study is to assess the link between heterogeneities in the lithosphere and different deformation patterns and styles along the orogen-foreland system of the Central Andes. First, we performed a 3D integration of new geological and geophysical data with previous models through forward modelling of Bouguer anomalies. Subsequently, a geodynamic model was set-up and parametrized from the previously obtained 3D structure and composition. We do not find a unambigous correlation between the resulting density configuration and terrane boundaries proposed by other authors. Our models reproduce the observed Bouguer anomaly and deformation patterns in the foreland. We find that thin-skinned deformation in the Subandean fold-and thrust belt is controlled by a thick sedimentary layer and coeval underthrusting of thin crust of the foreland beneath the thick crust of the Andean Plateau. In the adjacent thick-skinned deformation province of the inverted Cretaceous extensional Santa Barbara System sedimentary strata are much thinner and crustal thickness transitions from greater values in the Andean to a more reduced thickness in the foreland. Our results show that deformation processes occur where the highest gradients of lithospheric strength are present between the orogen and the foreland, thus suggesting a spatial correlation between deformation and lithospheric strength.
KW  - Central Andes
KW  - Lithospheric structure
KW  - Gravity modelling
KW  - Geodynamic modelling
KW  - Deformation
Y1  - 2019
U6  - https://doi.org/10.1016/j.tecto.2019.06.025
SN  - 0040-1951
SN  - 1879-3266
VL  - 766
SP  - 453
EP  - 468
PB  - Elsevier
CY  - Amsterdam
ER  -