TY - GEN A1 - Tofelde, Stefanie A1 - Bufe, Aaron A1 - Turowski, Jens M. T1 - Hillslope Sediment Supply Limits Alluvial Valley Width T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - River-valley morphology preserves information on tectonic and climatic conditions that shape landscapes. Observations suggest that river discharge and valley-wall lithology are the main controls on valley width. Yet, current models based on these observations fail to explain the full range of cross-sectional valley shapes in nature, suggesting hitherto unquantified controls on valley width. In particular, current models cannot explain the existence of paired terrace sequences that form under cyclic climate forcing. Paired river terraces are staircases of abandoned floodplains on both valley sides, and hence preserve past valley widths. Their formation requires alternating phases of predominantly river incision and predominantly lateral planation, plus progressive valley narrowing. While cyclic Quaternary climate changes can explain shifts between incision and lateral erosion, the driving mechanism of valley narrowing is unknown. Here, we extract valley geometries from climatically formed, alluvial river-terrace sequences and show that across our dataset, the total cumulative terrace height (here: total valley height) explains 90%–99% of the variance in valley width at the terrace sites. This finding suggests that valley height, or a parameter that scales linearly with valley height, controls valley width in addition to river discharge and lithology. To explain this valley-width-height relationship, we reformulate existing valley-width models and suggest that, when adjusting to new boundary conditions, alluvial valleys evolve to a width at which sediment removal from valley walls matches lateral sediment supply from hillslope erosion. Such a hillslope-channel coupling is not captured in current valley-evolution models. Our model can explain the existence of paired terrace sequences under cyclic climate forcing and relates valley width to measurable field parameters. Therefore, it facilitates the reconstruction of past climatic and tectonic conditions from valley topography. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1289 Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-572879 SN - 1866-8372 IS - 1289 ER - TY - JOUR A1 - Tofelde, Stefanie A1 - Bufe, Aaron A1 - Turowski, Jens M. T1 - Hillslope Sediment Supply Limits Alluvial Valley Width JF - AGU Advances N2 - River-valley morphology preserves information on tectonic and climatic conditions that shape landscapes. Observations suggest that river discharge and valley-wall lithology are the main controls on valley width. Yet, current models based on these observations fail to explain the full range of cross-sectional valley shapes in nature, suggesting hitherto unquantified controls on valley width. In particular, current models cannot explain the existence of paired terrace sequences that form under cyclic climate forcing. Paired river terraces are staircases of abandoned floodplains on both valley sides, and hence preserve past valley widths. Their formation requires alternating phases of predominantly river incision and predominantly lateral planation, plus progressive valley narrowing. While cyclic Quaternary climate changes can explain shifts between incision and lateral erosion, the driving mechanism of valley narrowing is unknown. Here, we extract valley geometries from climatically formed, alluvial river-terrace sequences and show that across our dataset, the total cumulative terrace height (here: total valley height) explains 90%–99% of the variance in valley width at the terrace sites. This finding suggests that valley height, or a parameter that scales linearly with valley height, controls valley width in addition to river discharge and lithology. To explain this valley-width-height relationship, we reformulate existing valley-width models and suggest that, when adjusting to new boundary conditions, alluvial valleys evolve to a width at which sediment removal from valley walls matches lateral sediment supply from hillslope erosion. Such a hillslope-channel coupling is not captured in current valley-evolution models. Our model can explain the existence of paired terrace sequences under cyclic climate forcing and relates valley width to measurable field parameters. Therefore, it facilitates the reconstruction of past climatic and tectonic conditions from valley topography. Y1 - 2022 U6 - https://doi.org/10.1029/2021AV000641 SN - 2576-604X PB - American Geophysical Union (AGU); Wiley CY - Hoboken, New Jersey, USA ER - TY - GEN A1 - Arboleda-Zapata, Mauricio A1 - Angelopoulos, Michael A1 - Overduin, Pier Paul A1 - Grosse, Guido A1 - Jones, Benjamin M. A1 - Tronicke, Jens T1 - Exploring the capabilities of electrical resistivity tomography to study subsea permafrost T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Sea level rise and coastal erosion have inundated large areas of Arctic permafrost. Submergence by warm and saline waters increases the rate of inundated permafrost thaw compared to sub-aerial thawing on land. Studying the contact between the unfrozen and frozen sediments below the seabed, also known as the ice-bearing permafrost table (IBPT), provides valuable information to understand the evolution of sub-aquatic permafrost, which is key to improving and understanding coastal erosion prediction models and potential greenhouse gas emissions. In this study, we use data from 2D electrical resistivity tomography (ERT) collected in the nearshore coastal zone of two Arctic regions that differ in their environmental conditions (e.g., seawater depth and resistivity) to image and study the subsea permafrost. The inversion of 2D ERT data sets is commonly performed using deterministic approaches that favor smoothed solutions, which are typically interpreted using a user-specified resistivity threshold to identify the IBPT position. In contrast, to target the IBPT position directly during inversion, we use a layer-based model parameterization and a global optimization approach to invert our ERT data. This approach results in ensembles of layered 2D model solutions, which we use to identify the IBPT and estimate the resistivity of the unfrozen and frozen sediments, including estimates of uncertainties. Additionally, we globally invert 1D synthetic resistivity data and perform sensitivity analyses to study, in a simpler way, the correlations and influences of our model parameters. The set of methods provided in this study may help to further exploit ERT data collected in such permafrost environments as well as for the design of future field experiments. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1285 Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-571234 SN - 1866-8372 IS - 1285 SP - 4423 EP - 4445 ER - TY - JOUR A1 - Arboleda-Zapata, Mauricio A1 - Angelopoulos, Michael A1 - Overduin, Pier Paul A1 - Grosse, Guido A1 - Jones, Benjamin M. A1 - Tronicke, Jens T1 - Exploring the capabilities of electrical resistivity tomography to study subsea permafrost JF - The Cryosphere N2 - Sea level rise and coastal erosion have inundated large areas of Arctic permafrost. Submergence by warm and saline waters increases the rate of inundated permafrost thaw compared to sub-aerial thawing on land. Studying the contact between the unfrozen and frozen sediments below the seabed, also known as the ice-bearing permafrost table (IBPT), provides valuable information to understand the evolution of sub-aquatic permafrost, which is key to improving and understanding coastal erosion prediction models and potential greenhouse gas emissions. In this study, we use data from 2D electrical resistivity tomography (ERT) collected in the nearshore coastal zone of two Arctic regions that differ in their environmental conditions (e.g., seawater depth and resistivity) to image and study the subsea permafrost. The inversion of 2D ERT data sets is commonly performed using deterministic approaches that favor smoothed solutions, which are typically interpreted using a user-specified resistivity threshold to identify the IBPT position. In contrast, to target the IBPT position directly during inversion, we use a layer-based model parameterization and a global optimization approach to invert our ERT data. This approach results in ensembles of layered 2D model solutions, which we use to identify the IBPT and estimate the resistivity of the unfrozen and frozen sediments, including estimates of uncertainties. Additionally, we globally invert 1D synthetic resistivity data and perform sensitivity analyses to study, in a simpler way, the correlations and influences of our model parameters. The set of methods provided in this study may help to further exploit ERT data collected in such permafrost environments as well as for the design of future field experiments. Y1 - 2022 U6 - https://doi.org/10.5194/tc-16-4423-2022 SN - 1994-0424 VL - 16 SP - 4423 EP - 4445 PB - Copernicus CY - Katlenburg-Lindau ER - TY - GEN A1 - Atmani, Farid A1 - Bookhagen, Bodo A1 - Smith, Taylor T1 - Measuring Vegetation Heights and Their Seasonal Changes in the Western Namibian Savanna Using Spaceborne Lidars T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) with its land and vegetation height data product (ATL08), and Global Ecosystem Dynamics Investigation (GEDI) with its terrain elevation and height metrics data product (GEDI Level 2A) missions have great potential to globally map ground and canopy heights. Canopy height is a key factor in estimating above-ground biomass and its seasonal changes; these satellite missions can also improve estimated above-ground carbon stocks. This study presents a novel Sparse Vegetation Detection Algorithm (SVDA) which uses ICESat-2 (ATL03, geolocated photons) data to map tree and vegetation heights in a sparsely vegetated savanna ecosystem. The SVDA consists of three main steps: First, noise photons are filtered using the signal confidence flag from ATL03 data and local point statistics. Second, we classify ground photons based on photon height percentiles. Third, tree and grass photons are classified based on the number of neighbors. We validated tree heights with field measurements (n = 55), finding a root-mean-square error (RMSE) of 1.82 m using SVDA, GEDI Level 2A (Geolocated Elevation and Height Metrics product): 1.33 m, and ATL08: 5.59 m. Our results indicate that the SVDA is effective in identifying canopy photons in savanna ecosystems, where ATL08 performs poorly. We further identify seasonal vegetation height changes with an emphasis on vegetation below 3 m; widespread height changes in this class from two wet-dry cycles show maximum seasonal changes of 1 m, possibly related to seasonal grass-height differences. Our study shows the difficulties of vegetation measurements in savanna ecosystems but provides the first estimates of seasonal biomass changes. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1275 KW - ICESat-2 KW - GEDI KW - canopy height KW - lidar KW - savanna Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-569915 SN - 1866-8372 IS - 1275 ER - TY - JOUR A1 - Atmani, Farid A1 - Bookhagen, Bodo A1 - Smith, Taylor T1 - Measuring vegetation heights and their seasonal changes in the Western Namibian Savanna using spaceborne lidars JF - Remote sensing / Molecular Diversity Preservation International (MDPI) N2 - The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) with its land and vegetation height data product (ATL08), and Global Ecosystem Dynamics Investigation (GEDI) with its terrain elevation and height metrics data product (GEDI Level 2A) missions have great potential to globally map ground and canopy heights. Canopy height is a key factor in estimating above-ground biomass and its seasonal changes; these satellite missions can also improve estimated above-ground carbon stocks. This study presents a novel Sparse Vegetation Detection Algorithm (SVDA) which uses ICESat-2 (ATL03, geolocated photons) data to map tree and vegetation heights in a sparsely vegetated savanna ecosystem. The SVDA consists of three main steps: First, noise photons are filtered using the signal confidence flag from ATL03 data and local point statistics. Second, we classify ground photons based on photon height percentiles. Third, tree and grass photons are classified based on the number of neighbors. We validated tree heights with field measurements (n = 55), finding a root-mean-square error (RMSE) of 1.82 m using SVDA, GEDI Level 2A (Geolocated Elevation and Height Metrics product): 1.33 m, and ATL08: 5.59 m. Our results indicate that the SVDA is effective in identifying canopy photons in savanna ecosystems, where ATL08 performs poorly. We further identify seasonal vegetation height changes with an emphasis on vegetation below 3 m; widespread height changes in this class from two wet-dry cycles show maximum seasonal changes of 1 m, possibly related to seasonal grass-height differences. Our study shows the difficulties of vegetation measurements in savanna ecosystems but provides the first estimates of seasonal biomass changes. KW - ICESat-2 KW - GEDI KW - canopy height KW - lidar KW - savanna Y1 - 2022 U6 - https://doi.org/10.3390/rs14122928 SN - 2072-4292 VL - 14 IS - 12 SP - 1 EP - 20 PB - MDPI CY - Basel, Schweiz ET - 12 ER - TY - THES A1 - Esfahani, Reza Dokht Dolatabadi T1 - Time-dependent monitoring of near-surface and ground motion modelling: developing new data processing approaches based on Music Information Retrieval (MIR) strategies N2 - Seismology, like many scientific fields, e.g., music information retrieval and speech signal pro- cessing, is experiencing exponential growth in the amount of data acquired by modern seismo- logical networks. In this thesis, I take advantage of the opportunities offered by "big data" and by the methods developed in the areas of music information retrieval and machine learning to predict better the ground motion generated by earthquakes and to study the properties of the surface layers of the Earth. In order to better predict seismic ground motions, I propose two approaches based on unsupervised deep learning methods, an autoencoder network and Generative Adversarial Networks. The autoencoder technique explores a massive amount of ground motion data, evaluates the required parameters, and generates synthetic ground motion data in the Fourier amplitude spectra (FAS) domain. This method is tested on two synthetic datasets and one real dataset. The application on the real dataset shows that the substantial information contained within the FAS data can be encoded to a four to the five-dimensional manifold. Consequently, only a few independent parameters are required for efficient ground motion prediction. I also propose a method based on Conditional Generative Adversarial Networks (CGAN) for simulating ground motion records in the time-frequency and time domains. CGAN generates the time-frequency domains based on the parameters: magnitude, distance, and shear wave velocities to 30 m depth (VS30). After generating the amplitude of the time-frequency domains using the CGAN model, instead of classical conventional methods that assume the amplitude spectra with a random phase spectrum, the phase of the time-frequency domains is recovered by minimizing the observed and reconstructed spectrograms. In the second part of this dissertation, I propose two methods for the monitoring and characterization of near-surface materials and site effect analyses. I implement an autocorrelation function and an interferometry method to monitor the velocity changes of near-surface materials resulting from the Kumamoto earthquake sequence (Japan, 2016). The observed seismic velocity changes during the strong shaking are due to the non-linear response of the near-surface materials. The results show that the velocity changes lasted for about two months after the Kumamoto mainshock. Furthermore, I used the velocity changes to evaluate the in-situ strain-stress relationship. I also propose a method for assessing the site proxy "VS30" using non-invasive analysis. In the proposed method, a dispersion curve of surface waves is inverted to estimate the shear wave velocity of the subsurface. This method is based on the Dix-like linear operators, which relate the shear wave velocity to the phase velocity. The proposed method is fast, efficient, and stable. All of the methods presented in this work can be used for processing "big data" in seismology and for the analysis of weak and strong ground motion data, to predict ground shaking, and to analyze site responses by considering potential time dependencies and nonlinearities. KW - ground motion modeling KW - machine learning KW - near-surface monitoring KW - imaging KW - generative model KW - surface wave Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-567671 ER - TY - THES A1 - Schuster, Valerian T1 - Mechanical and hydraulic properties of Opalinus Clay T1 - Mechanische und hydraulische Eigenschaften von Opalinuston BT - influence of compositional heterogeneity and thermodynamic boundary conditions BT - Einfluss von kompositorischer Heterogenität und thermodynamischen Randbedingungen N2 - Deep geological repositories represent a promising solution for the final disposal of nuclear waste. Due to its low permeability, high sorption capacity and self-sealing potential, Opalinus Clay (OPA) is considered a suitable host rock formation for the long-term storage of nuclear waste in Switzerland and Germany. However, the clay formation is characterized by compositional and structural variabilities including the occurrence of carbonate- and quartz-rich layers, pronounced bedding planes as well as tectonic elements such as pre-existing fault zones and fractures, suggesting heterogeneous rock mass properties. Characterizing the heterogeneity of host rock properties is therefore essential for safety predictions of future repositories. This includes a detailed understanding of the mechanical and hydraulic properties, deformation behavior and the underlying deformation processes for an improved assessment of the sealing integrity and long-term safety of a deep repository in OPA. Against this background, this thesis presents the results of deformation experiments performed on intact and artificially fractured specimens of the quartz-rich, sandy and clay-rich, shaly facies of OPA. The experiments focus on the influence of mineralogical composition on the deformation behavior as well as the reactivation and sealing properties of pre-existing faults and fractures at different boundary conditions (e.g., pressure, temperature, strain rate). The anisotropic mechanical properties of the sandy facies of OPA are presented in the first section, which were determined from triaxial deformation experiments using dried and resaturated samples loaded at 0°, 45° and 90° to the bedding plane orientation. A Paterson-type deformation apparatus was used that allowed to investigate how the deformation behavior is influenced by the variation of confining pressure (50 – 100 MPa), temperature (25 – 200 °C), and strain rate (1 × 10-3 – 5 × 10-6 s-1). Constant strain rate experiments revealed brittle to semi-brittle deformation behavior of the sandy facies at the applied conditions. Deformation behavior showed a strong dependence on confining pressure, degree of water saturation as well as bedding orientation, whereas the variation of temperature and strain rate had no significant effect on deformation. Furthermore, the sandy facies displays higher strength and stiffness compared to the clay-rich shaly facies deformed at similar conditions by Nüesch (1991). From the obtained results it can be concluded that cataclastic mechanisms dominate the short-term deformation behavior of dried samples from both facies up to elevated pressure (<200 MPa) and temperature (<200 °C) conditions. The second part presents triaxial deformation tests that were performed to investigate how structural discontinuities affect the deformation behavior of OPA and how the reactivation of preexisting faults is influenced by mineral composition and confining pressure. To this end, dried cylindrical samples of the sandy and shaly facies of OPA were used, which contained a saw-cut fracture oriented at 30° to the long axis. After hydrostatic pre-compaction at 50 MPa, constant strain rate deformation tests were performed at confining pressures of 5, 20 or 35 MPa. With increasing confinement, a gradual transition from brittle, highly localized fault slip including a stress drop at fault reactivation to semi-brittle deformation behavior, characterized by increasing delocalization and non-linear strain hardening without dynamic fault reactivation, can be observed. Brittle localization was limited by the confining pressure at which the fault strength exceeded the matrix yield strength, above which strain partitioning between localized fault slip and distributed matrix deformation occurred. The sandy facies displayed a slightly higher friction coefficient (≈0.48) compared to the shaly facies (≈0.4). In addition, slide-hold-slide tests were conducted, revealing negative or negligible frictional strengthening, which suggests stable creep and long-term weakness of faults in both facies of OPA. The conducted experiments demonstrate that dilatant brittle fault reactivation in OPA may be favored at high overconsolidation ratios and shallow depths, increasing the risk of seismic hazard and the creation of fluid pathways. The final section illustrates how the sealing capacity of fractures in OPA is affected by mineral composition. Triaxial flow-through experiments using Argon-gas were performed with dried samples from the sandy and shaly facies of OPA containing a roughened, artificial fracture. Slate, graywacke, quartzite, natural fault gouge, and granite samples were also tested to highlight the influence of normal stress, mineralogy and diagenesis on the sustainability of fracture transmissivity. With increasing normal stress, a non-linear decrease of fracture transmissivity can be observed that resulted in a permanent reduction of transmissivity after stress release. The transmissivity of rocks with a high portion of strong minerals (e.g., quartz) and high unconfined compressive strength was less sensitive to stress changes. In accordance with this, the sandy facies of OPA displayed a higher initial transmissivity that was less sensitive to stress changes compared to the shaly facies. However, transmissivity of rigid slate was less sensitive to stress changes than the sandy facies of OPA, although the slate is characterized by a higher phyllosilicate content. This demonstrates that in addition to mineral composition, other factors such as the degree of metamorphism, cementation and consolidation have to be considered when evaluating the sealing capacity of phyllosilicate-rich rocks. The results of this thesis highlighted the role of confining pressure on the failure behavior of intact and artificially fractured OPA. Although the quartz-rich sandy facies may be considered as being more favorable for underground constructions due to its higher shear strength and stiffness than the shaly facies, the results indicate that when fractures develop in the sandy facies, they are more conductive and remain more permeable compared to fractures in the clay-dominated shaly facies at a given stress. The results may provide the basis for constitutive models to predict the integrity and evolution of a future repository. Clearly, the influence of composition and consolidation, e.g., by geological burial and uplift, on the mechanical sealing behavior of OPA highlights the need for a detailed site-specific material characterization for a future repository. N2 - Geologische Tiefenlager stellen eine vielversprechende Lösung für die Endlagerung von Atommüll dar. Aufgrund seiner geringen hydraulischen Durchlässigkeit, hohen Sorptionskapazität von Schadstoffen sowie seines Selbstabdichtungspotentials von Rissen gilt Opalinuston (OPA) als geeignetes Wirtsgestein für die Langzeitlagerung von Atommüll in der Schweiz und in Deutschland. Die Tonformation weist jedoch eine lithologische und strukturelle Variabilität auf, die durch das Auftreten von karbonat- und quarzreichen Lagen, einer ausgeprägten Schichtung sowie tektonischen Elementen wie Störungszonen und Brüchen gekennzeichnet ist, was auf heterogene Gebirgseigenschaften hindeutet. Die Charakterisierung dieser Heterogenität im Hinblick auf die Eigenschaften des Wirtsgesteins ist für Sicherheitsvorhersagen zukünftiger Endlager von wesentlicher Bedeutung. Diese beinhaltet ein detailliertes Verständnis der mechanischen und hydraulischen Eigenschaften, des Deformationsverhaltens sowie der zugrunde liegenden Deformationsprozesse, die eine verbesserte Beurteilung des wirksamen Einschlusses sowie der Langzeitsicherheit eines Tiefenlagers in OPA ermöglichen. Vor diesem Hintergrund präsentiert diese Arbeit die Ergebnisse von triaxialen Verformungsexperimenten, die an intakten und künstlich gestörten Proben der quarzreichen, sandigen sowie tonigen Fazies von OPA durchgeführt worden sind. Ein besonderer Fokus ist hierbei auf den Einfluss der mineralogischen Zusammensetzung auf das Verformungsverhalten sowie die Reaktivierungs- und Abdichtungseigenschaften von bereits bestehenden Scherzonen und Rissen bei unterschiedlichen Randbedingungen (z. B. Druck, Temperatur, Dehnungsrate) gelegt worden. Im ersten Abschnitt werden die anisotropen mechanischen Eigenschaften der sandigen Fazies von OPA vorgestellt. Hierfür sind triaxiale Verformungsexperimente an getrockneten und wassergesättigten Proben durchgeführt worden, die in einem Winkel von 0°, 45° und 90° zur relativ zur vorhandenen Schichtung belastet worden sind. Mittels einer Paterson Gasdruckapparatur ist der Einfluss von Mantelspannung (50 – 100 MPa), Temperatur (25 – 200 °C) und Verformungsrate (1 × 10-3 – 5 × 10-6 s-1) auf das Deformationsverhalten untersucht worden. Die Experimente zeigen ein sprödes bis halbsprödes Verformungsverhalten der sandigen Fazies, wobei ein deutlicher Einfluss von Manteldruck, Wassersättigung sowie Schichtungsorientierung festgestellt werden konnte. Im Gegensatz dazu zeigt die Änderung von Temperatur und Verformungsrate keinen signifikanten Einfluss auf das Deformationsverhalten und die Festigkeitseigenschaften der sandigen Fazies. Verglichen mit der tonigen Fazies (Nüesch 1991) weist die sandige Fazies des OPA eine höhere Festigkeit und Steifigkeit auf. Die Ergebnisse deuten darauf hin, dass das kurzfristige Verformungsverhalten getrockneter Proben beider Faziestypen bis zu erhöhten Druck- (<200 MPa) und Temperaturbedingungen (<200 °C) von kataklastischen Deformationsmechanismen dominiert wird. Im zweiten Teil werden die Ergebnisse von triaxialen Deformationsexperimenten beschrieben, die durchgeführt worden sind, um den Einfluss von bereits bestehenden Störungen auf das Verformungsverhalten von OPA zu untersuchen und wie die Reaktivierung von Scherflächen durch die Mineralzusammensetzung und den Manteldruck beeinflusst wird. Dazu sind getrocknete zylindrische Proben der sandigen und tonigen Fazies von OPA verwendet worden, die zuvor in einem Winkel von 30° zur Längsachse halbiert worden sind. Nach einer hydrostatischen Vorkonsolidierung bei 50 MPa Druck, sind die Proben bei einer konstanten axialen Verformungsrate und Mantelspannungen von 5, 20 und 35 MPa deformiert worden. Bei niedriger Mantelspannung wird die Reaktivierung der Scherfläche durch einen Spannungsabfall eingeleitet, wobei weitere Verformung durch stark lokalisierte Scherung aufgenommen wird. Mit zunehmender Mantelspannung kann ein Übergang zu halbsprödem Verformungsverhalten beobachtet werden, das durch einen zunehmenden Anteil von Matrixdeformation ohne dynamische Verwerfungsreaktivierung gekennzeichnet ist. Dabei weist die sandige Fazies einen höheren Reibungskoeffizienten (≈0,48) als die tonige Fazies (≈0,4) auf. Die Experimente zeigen, dass spröde Reaktivierung der Scherfläche bis zu einer Mantelspannung erfolgt, ab der die Scherfestigkeit der künstlichen Störung die Fließspannung der Matrix übersteigt. Entsprechend beginnt mit weiter ansteigender Mantelspannung die Partitionierung von Deformation in Scherung und Matrixverformung. Relaxations- und Wiederbelastungstests (Slide-Hold-Slide) zeigen negative bzw. vernachlässigbare Reibungsverheilung auf, was auf eine geringe Wiederverfestigung und folglich aseismisches Kriechen als Langzeitverhalten von Scherzonen in OPA hindeutet. Die Ergebnisse zeigen, dass die spröde Reaktivierung von Scherzonen in OPA durch eine starke Überkonsolidierung und in geringen Tiefen begünstigt werden kann, was das Risiko von Seismizität und die Bildung hydraulischer Fließwege erhöht. Der letzte Abschnitt veranschaulicht, wie die Transmissivität von Rissen in OPA von der wirkenden Normalspannung und Mineralzusammensetzung beeinflusst wird. Hierfür sind triaxiale Durchströmungsexperimente an getrockneten Proben der sandigen und tonigen Fazies von OPA durchgeführt worden, die eine künstlich angeraute Rissfläche enthielten. Um den Einfluss von Normalspannung, Mineralogie und Diagenese auf die hydraulische Rissverschließung zu untersuchen, sind darüber hinaus auch Risse in Schiefer, Grauwacke, Quarzit, Proben aus natürlichen Störungszonen und Granit getestet worden. Mit zunehmender Normalspannung konnte eine nichtlineare Abnahme der Risstransmissivität beobachtet werden, die nach Entlastung zu einer irreversiblen Reduktion der Transmissivität führt. Die Transmissivität von Gesteinen, die durch einen hohen Anteil mechanisch fester Minerale (z.B. Quarz) sowie einer hohen einaxialen Druckfestigkeit charakterisiert werden, reagieren robuster auf Spannungsänderungen. Dementsprechend zeigt die sandige Fazies von OPA im Vergleich zur tonigen Fazies eine höhere initale Risstransmissivität, die weniger empfindlich auf Spannungsänderungen reagiert. Obwohl die sandige Fazies im Vergleich zu der untersuchten Schieferprobe einen niedrigeren Schichtsilikatgehalt aufweist, reagiert die Risstransmissivität des Schiefers deutlich geringer auf Spannungsänderungen. Aus den Experimenten kann abgeleitet werden, dass für die Bewertung der hydraulischen Rissverschließung in schichtsilikatreichen Gesteinen neben der mineralischen Zusammensetzung weitere Faktoren, wie der Grad der Metamorphose sowie Zementierung und Konsolidierung, berücksichtigt werden müssen. Die Ergebnisse dieser Arbeit verdeutlichten die Rolle der Mantelspannung auf das Deformationsverhalten von intaktem und künstlich gestörten OPA. Obwohl die quarzreiche sandige Fazies von OPA aufgrund ihrer höheren Scherfestigkeit und Steifigkeit als günstiger für die Konstruktion von Untertagebauwerken angesehen werden kann, weisen die präsentierten Ergebnisse darauf hin, dass diese vorteilhaften mechanischen Eigenschaften mit einer Verringerung der hydraulischen Abdichtungskapazität verbunden sind, d.h. wenn sich Risse in der sandigen Fazies entwickeln, sind diese hydraulisch leitfähiger und bleiben durchlässiger im Vergleich zu Rissen in der tonigen Fazies bei einer gegebenen Spannung. Die Ergebnisse können die Grundlage für die Entwicklung konstitutiver Modelle bilden, die zur Einschätzung der Integrität eines zukünftigen Endlagers herangezogen werden können. Der Einfluss der mineralogischen Zusammensetzung sowie der Konsolidierung auf die mechanischen und hydraulischen Eigenschaften von OPA zeigen die Notwendigkeit einer detaillierten, standortspezifischen Materialcharakterisierung für ein zukünftiges Endlager. KW - Opalinus Clay KW - triaxial deformation experiments KW - microstructural deformation mechanisms KW - fault reactivation KW - fracture transmissivity KW - Opalinuston KW - Reaktivierung von Störungszonen KW - Risstransmissivität KW - Mikrostrukturelle KW - Deformationsmechanismen KW - triaxiale Deformationsexperimente Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-566786 ER - TY - GEN A1 - Heistermann, Maik A1 - Bogena, Heye A1 - Francke, Till A1 - Güntner, Andreas A1 - Jakobi, Jannis A1 - Rasche, Daniel A1 - Schrön, Martin A1 - Döpper, Veronika A1 - Fersch, Benjamin A1 - Groh, Jannis A1 - Patil, Amol A1 - Pütz, Thomas A1 - Reich, Marvin A1 - Zacharias, Steffen A1 - Zengerle, Carmen A1 - Oswald, Sascha T1 - Soil moisture observation in a forested headwater catchment: combining a dense cosmic-ray neutron sensor network with roving and hydrogravimetry at the TERENO site Wüstebach T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Cosmic-ray neutron sensing (CRNS) has become an effective method to measure soil moisture at a horizontal scale of hundreds of metres and a depth of decimetres. Recent studies proposed operating CRNS in a network with overlapping footprints in order to cover root-zone water dynamics at the small catchment scale and, at the same time, to represent spatial heterogeneity. In a joint field campaign from September to November 2020 (JFC-2020), five German research institutions deployed 15 CRNS sensors in the 0.4 km2 Wüstebach catchment (Eifel mountains, Germany). The catchment is dominantly forested (but includes a substantial fraction of open vegetation) and features a topographically distinct catchment boundary. In addition to the dense CRNS coverage, the campaign featured a unique combination of additional instruments and techniques: hydro-gravimetry (to detect water storage dynamics also below the root zone); ground-based and, for the first time, airborne CRNS roving; an extensive wireless soil sensor network, supplemented by manual measurements; and six weighable lysimeters. Together with comprehensive data from the long-term local research infrastructure, the published data set (available at https://doi.org/10.23728/b2share.756ca0485800474e9dc7f5949c63b872; Heistermann et al., 2022) will be a valuable asset in various research contexts: to advance the retrieval of landscape water storage from CRNS, wireless soil sensor networks, or hydrogravimetry; to identify scale-specific combinations of sensors and methods to represent soil moisture variability; to improve the understanding and simulation of land–atmosphere exchange as well as hydrological and hydrogeological processes at the hillslope and the catchment scale; and to support the retrieval of soil water content from airborne and spaceborne remote sensing platforms. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1272 Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-567756 SN - 1866-8372 IS - 1272 SP - 2501 EP - 2519 ER - TY - BOOK A1 - Trauth, Martin H. T1 - Python Recipes for Earth Sciences T3 - Springer Textbooks in Earth Sciences, Geography and Environment N2 - Python is used in a wide range of geoscientific applications, such as in processing images for remote sensing, in generating and processing digital elevation models, and in analyzing time series. This book introduces methods of data analysis in the geosciences using Python that include basic statistics for univariate, bivariate, and multivariate data sets, time series analysis, and signal processing; the analysis of spatial and directional data; and image analysis. The text includes numerous examples that demonstrate how Python can be used on data sets from the earth sciences. The supplementary electronic material (available online through Springer Link) contains the example data as well as recipes that include all the Python commands featured in the book. KW - computational geosciences KW - geoinformatics KW - geostatistics KW - mathematical geology KW - geomodeling KW - digital elevation models KW - climate time series analysis Y1 - 2022 SN - 978-3-031-07719-7 SN - 978-3-031-07718-0 SN - 978-3-031-07720-3 SN - 978-3-031-07721-0 U6 - https://doi.org/10.1007/978-3-031-07719-7 SN - 2510-1307 SN - 2510-1315 PB - Springer CY - Cham ER -