Refine
Year of publication
- 2015 (33) (remove)
Document Type
- Doctoral Thesis (33) (remove)
Language
- English (33) (remove)
Is part of the Bibliography
- yes (33)
Keywords
- Erosion (2)
- Seesedimente (2)
- Simulation (2)
- Wasser (2)
- erosion (2)
- lake sediments (2)
- numerische Modellierung (2)
- simulation (2)
- stabile Isotope (2)
- water (2)
- Abschätzung der Unsicherheiten (1)
- Altlasten (1)
- Antwortspektren (1)
- Argentina (1)
- Argentinien (1)
- Blattwachse (1)
- Boden (1)
- Bodenbewegung (1)
- Bodenbewegungsmodelle (1)
- Carbo-Iron (1)
- Carbo-Iron® (1)
- Cerrado (1)
- Computational Fluid Dynamics (CFD) (1)
- Coulomb stress (1)
- Coulombspannung (1)
- DANSER (1)
- Datenfilter (1)
- Dauer der Bodenbewegung (1)
- Dead Sea (1)
- Deformation (1)
- Denitrifikation (1)
- Denudation (1)
- ETAS Modell (1)
- ETAS model (1)
- East African Rift (1)
- Eastern Cordillera (1)
- Electrical Resistivity Tomography (ERT) (1)
- Elektrische Widerstandstomographie (ERT) (1)
- EnMAP Satellit (1)
- EnMAP satellite (1)
- Erdbeben (1)
- Erdbebengefährdungsabschätzungen (1)
- Erdbebenvorhersage (1)
- Erdbebenwechselwirkung (1)
- Erdmantel (1)
- Eulerian grid (1)
- Eulerische Gitter (1)
- Eurasian active margin (1)
- Eurasischer aktiver Kontinentalrand (1)
- Exhumationsprozesse (1)
- Fernerkundung (1)
- Flussbettmorphologie (1)
- Fourier spectra (1)
- Fourier-Spektren (1)
- Gashydrate (1)
- Geologie (1)
- Geophysik (1)
- Ground Motion Prediction Equation (GMPE) (1)
- HP/LT metamorphism (1)
- HP/LT-Metamorphose (1)
- Hangerosion (1)
- Hochwasser (1)
- Hochwasserrekonstruktion (1)
- Hyperspektral (1)
- Isábena Einzugsgebiet (1)
- Isábena catchment (1)
- Karbonate (1)
- Klimawandel (1)
- Kohlenstoffspeicher (1)
- Kolloidtransport (1)
- Koppelung (1)
- Küstenerosion (1)
- Landnutzung (1)
- Landnutzungswandel (1)
- Landschaftsentwicklung (1)
- Magnetotellurik (1)
- Massenversatzprozesse (1)
- Mineralreaktion (1)
- Modellierung (1)
- Nachbeben (1)
- Nanoeisen (1)
- Neotektonik (1)
- Niger (1)
- Oberfläche (1)
- Oberflächenprozesse (1)
- Ostkordillere (1)
- Paläoaltimetrie (1)
- Paläoklima (1)
- Paläotektonik (1)
- Pamir (1)
- Plateau (1)
- Pontiden (1)
- Pontides (1)
- Puna (1)
- SEC (1)
- Sanierung (1)
- Sediment Fingerprinting (1)
- Sedimenttransport (1)
- Seismologie (1)
- Seismology (1)
- Seltenerdelemente (1)
- Software (1)
- Spektroskopie (1)
- Tektonik (1)
- Tian-Shan (1)
- Tiefendeformation (1)
- Tien-Shan (1)
- Totes Meer (1)
- U-Pb Geochronologie (1)
- U-Pb geochronology (1)
- Umweltmonitoring (1)
- Variabilität von Bodenbewegung (1)
- Vegetationsbedeckung (1)
- Warven (1)
- Zeitreihenanalyse (1)
- aftershocks (1)
- artificial mixtures (1)
- carbonates (1)
- climate change (1)
- coastal erosion (1)
- colloid transport (1)
- cosmogenic radionuclides (1)
- coupling (1)
- data filtering (1)
- deforestation (1)
- deformation (1)
- denitrification (1)
- denudation processes (1)
- duration (1)
- early earth tectonics (1)
- earth's mantle (1)
- earthquake (1)
- earthquake forecasting (1)
- earthquake interaction (1)
- ecohydrology (1)
- environmental monitoring (1)
- exhumation processes (1)
- finite Differenzen (1)
- finite Elemente (1)
- finite differences (1)
- finite elements (1)
- flood (1)
- flood reconstruction (1)
- fluvial incision (1)
- fluviale Einschneidung (1)
- geology (1)
- geophysics (1)
- ground motion variability (1)
- ground motions (1)
- hillslope diffusion (1)
- historical earthquakes (1)
- historische Erdbeben (1)
- hydrate (1)
- hyperspectral (1)
- hyporheic zone (1)
- hyporheische Zone (1)
- in-situ remediation (1)
- isotopes (1)
- kosmogene Nuklide (1)
- land use change (1)
- landscape evolution (1)
- leaf wax (1)
- magnetotellurics (1)
- mass wasting (1)
- mineral reaction (1)
- modeling (1)
- modelling (1)
- nanoscale zero-valent iron (nZVI) (1)
- neotectonics (1)
- numerical model (1)
- numerical modeling (1)
- numerische Strömungsmechanik (1)
- ostafrikanisches Riftsystem (1)
- palaeoclimate (1)
- paleoaltimetry (1)
- plateau (1)
- rare earth elements (1)
- rate-state friction (1)
- reactive transport groundwater model (1)
- reaktives Grundwassermodell (1)
- remote sensing (1)
- response spectra (1)
- sediment fingerprinting (1)
- sediment transport (1)
- seismic hazard (1)
- seismic risk (1)
- seismisches Risiko (1)
- seltene Erden (1)
- soil (1)
- soil organic carbon (1)
- spectroscopy (1)
- stable isotopes (1)
- statistical seismology (1)
- statistische Seismologie (1)
- streambed morphology (1)
- subduction-accretionary complexes (1)
- subduktions-akkretions Komplexe (1)
- surface (1)
- surface evolution (1)
- surface processes (1)
- suspended sediment (1)
- tectonics (1)
- thermo-mechanics (1)
- thermochemical mantle convection (1)
- thermochemischer Mantelkonvektion (1)
- thermochronology (1)
- time series analysis (1)
- transient earthquake patterns (1)
- transiente Erdbebenmuster (1)
- uncertainty estimation (1)
- varves (1)
- vegetation cover (1)
- volcanic glass (1)
- vulkanischer Gläser (1)
- Ökohydrologie (1)
Institute
- Institut für Geowissenschaften (33) (remove)
Stream water and groundwater are important fresh water resources but their water quality is deteriorated by harmful solutes introduced by human activities. The interface between stream water and the subsurface water is an important zone for retention, transformation and attenuation of these solutes. Streambed structures enhance these processes by increased water and solute exchange across this interface, denoted as hyporheic exchange.
This thesis investigates the influence of hydrological and morphological factors on hyporheic water and solute exchange as well as redox-reactions in fluvial streambed structures on the intermediate scale (10–30m). For this purpose, a three-dimensional numerical modeling approach for coupling stream water flow with porous media flow is used. Multiple steady state stream water flow scenarios over different generic pool-riffle morphologies and a natural in-stream gravel bar are simulated by a computational fluid dynamics code that provides the hydraulic head distribution at the streambed. These heads are subsequently used as the top boundary condition of a reactive transport groundwater model of the subsurface beneath the streambed. Ambient groundwater that naturally interacts with the stream water is considered in scenarios of different magnitudes of downwelling stream water (losing case) and upwelling groundwater (gaining case). Also, the neutral case, where stream stage and groundwater levels are balanced is considered. Transport of oxygen, nitrate and dissolved organic carbon and their reaction by aerobic respiration and denitrification are modeled.
The results show that stream stage and discharge primarily induce hyporheic exchange flux and solute transport with implications for specific residence times and reactions at both the fully and partially submerged structures. Gaining and losing conditions significantly diminish the extent of the hyporheic zone, the water exchange flux, and shorten residence times for both the fully and partially submerged structures. With increasing magnitude of gaining or losing conditions, these metrics exponentially decrease.
Stream water solutes are transported mainly advectively into the hyporheic zone and hence their influx corresponds directly to the infiltrating water flux. Aerobic respiration takes place in the shallow streambed sediments, coinciding to large parts with the extent of the hyporheic exchange flow. Denitrification occurs mainly as a “reactive fringe” surrounding the aerobic zone, where oxygen concentration is low and still a sufficient amount of stream water carbon source is available. The solute consumption rates and the efficiency of the aerobic and anaerobic reactions depend primarily on the available reactive areas and the residence times, which are both controlled by the interplay between hydraulic head distribution at the streambed and the gradients between stream stage and ambient groundwater. Highest solute consumption rates can be expected under neutral conditions, where highest solute flux, longest residence times and largest extent of the hyporheic exchange occur. The results of this thesis show that streambed structures on the intermediate scale have a significant potential to contribute to a net solute turnover that can support a healthy status of the aquatic ecosystem.
Analysis and modeling of transient earthquake patterns and their dependence on local stress regimes
(2015)
Investigations in the field of earthquake triggering and associated interactions, which includes aftershock triggering as well as induced seismicity, is important for seismic hazard assessment due to earthquakes destructive power. One of the approaches to study earthquake triggering and their interactions is the use of statistical earthquake models, which are based on knowledge of the basic seismicity properties, in particular, the magnitude distribution and spatiotemporal properties of the triggered events.
In my PhD thesis I focus on some specific aspects of aftershock properties, namely, the relative seismic moment release of the aftershocks with respect to the mainshocks; the spatial correlation between aftershock occurrence and fault deformation; and on the influence of aseismic transients on the aftershock parameter estimation. For the analysis of aftershock sequences I choose a statistical approach, in particular, the well known Epidemic Type Aftershock Sequence (ETAS) model, which accounts for the input of background and triggered seismicity. For my specific purposes, I develop two ETAS model modifications in collaboration with Sebastian Hainzl. By means of this approach, I estimate the statistical aftershock parameters and performed simulations of aftershock sequences as well.
In the case of seismic moment release of aftershocks, I focus on the ratio of cumulative seismic moment release with respect to the mainshocks. Specifically, I investigate the ratio with respect to the focal mechanism of the mainshock and estimate an effective magnitude, which represents the cumulative aftershock energy (similar to Bath's law, which defines the average difference between mainshock and the largest aftershock magnitudes). Furthermore, I compare the observed seismic moment ratios with the results of the ETAS simulations. In particular, I test a restricted ETAS (RETAS) model which is based on results of a clock advanced model and static stress triggering.
To analyze spatial variations of triggering parameters I focus in my second approach on the aftershock occurrence triggered by large mainshocks and the study of the aftershock parameter distribution and their spatial correlation with the coseismic/postseismic slip and interseismic locking. To invert the aftershock parameters I improve the modified ETAS (m-ETAS) model, which is able to take the extension of the mainshock rupture into account. I compare the results obtained by the classical approach with the output of the m-ETAS model.
My third approach is concerned with the temporal clustering of seismicity, which might not only be related to earthquake-earthquake interactions, but also to a time-dependent background rate, potentially biasing the parameter estimations. Thus, my coauthors and I also applied a modification of the ETAS model, which is able to take into account time-dependent background activity. It can be applicable for two different cases: when an aftershock catalog has a temporal incompleteness or when the background seismicity rate changes with time, due to presence of aseismic forces.
An essential part of any research is the testing of the developed models using observational data sets, which are appropriate for the particular study case. Therefore, in the case of seismic moment release I use the global seismicity catalog. For the spatial distribution of triggering parameters I exploit two aftershock sequences of the Mw8.8 2010 Maule (Chile) and Mw 9.0 2011 Tohoku (Japan) mainshocks. In addition, I use published geodetic slip models of different authors. To test our ability to detect aseismic transients my coauthors and I use the data sets from Western Bohemia (Central Europe) and California.
Our results indicate that:
(1) the seismic moment of aftershocks with respect to mainshocks depends on the static stress changes and is maximal for the normal, intermediate for thrust and minimal for strike-slip stress regimes, where the RETAS model shows a good correspondence with the results;
(2) The spatial distribution of aftershock parameters, obtained by the m-ETAS model, shows anomalous values in areas of reactivated crustal fault systems. In addition, the aftershock density is found to be correlated with coseismic slip gradient, afterslip, interseismic coupling and b-values. Aftershock seismic moment is positively correlated with the areas of maximum coseismic slip and interseismically locked areas. These correlations might be related to the stress level or to material properties variations in space;
(3) Ignoring aseismic transient forcing or temporal catalog incompleteness can lead to the significant under- or overestimation of the underlying trigger parameters. In the case when a catalog is complete, this method helps to identify aseismic sources.