Refine
Year of publication
- 2021 (143) (remove)
Document Type
- Article (97)
- Doctoral Thesis (26)
- Postprint (16)
- Monograph/Edited Volume (1)
- Conference Proceeding (1)
- Habilitation Thesis (1)
- Master's Thesis (1)
Is part of the Bibliography
- yes (143) (remove)
Keywords
- PHREEQC (5)
- reactive transport (4)
- Earthquake source observations (3)
- ALOS World 3D (2)
- ASTER GDEM (2)
- Alpen (2)
- Alps (2)
- Arctic Ocean (2)
- Argentina (2)
- Argentinien (2)
- Big Naryn complex (2)
- Copernicus DEM (2)
- DEM noise (2)
- Earthquake ground motions (2)
- Earthquake hazards (2)
- Environmental sciences (2)
- Exhumation (2)
- Forschungsmethodik (2)
- Fourier analysis (2)
- GNSS-integrated water vapour (2)
- Germany (2)
- Global Navigation Satellite System (GNSS) (2)
- HVSR (2)
- Kuilyu complex (2)
- Nearshore zone (2)
- Ocean color remote sensing (2)
- Ocean sciences (2)
- Paleoclimate (2)
- Paläoklimadynamik (2)
- Rheologie (2)
- SRTM (2)
- Solid Earth sciences (2)
- Soziale Medien (2)
- TRMM (2)
- TanDEM-X (2)
- Tianshan orogenic belt (2)
- Tonian–Cryogenian (2)
- Turbidity retrieval (2)
- Twitter (2)
- Unterrichtsmethoden (2)
- Varves (2)
- WorldDEM (2)
- Younger Dryas (2)
- acoustic emissions (2)
- blueSeis-3A sensors (2)
- calc-alkaline (2)
- central Poland (2)
- climate change (2)
- climate change adaptation (2)
- coherency (2)
- coherent noise (2)
- convective available potential energy (CAPE) (2)
- correlation (2)
- damage (2)
- earthquake source (2)
- elastic rock properties (2)
- environmental seismology (2)
- extreme rainfall (2)
- fatigue (2)
- fundamental frequency (2)
- governance (2)
- heterogeneity (2)
- heuristic analysis (2)
- huddle test (2)
- innovation (2)
- insurance (2)
- lake monitoring (2)
- lake sediments (2)
- magmatic arc (2)
- mass (2)
- mountain geomorphology (2)
- natural hazard (2)
- noise cross (2)
- numerical modeling (2)
- permafrost (2)
- preparedness (2)
- recovery (2)
- repository far-field (2)
- rotational seismology (2)
- sedimentation pattern (2)
- seismic monitoring (2)
- slope failure (2)
- social (2)
- sorption (2)
- source direction (2)
- time series (2)
- transferability (2)
- urban infill development (2)
- wasting (2)
- weathering (2)
- (compliant) cracks (1)
- 3D root (1)
- Abbaufrontkartierung (1)
- Abbildende Spektroskopie (1)
- African climate (1)
- Afrikanisches Klima (1)
- Afyon volcanics (1)
- AlpArray (1)
- Altersmodelierung (1)
- Aluminium– silicates (1)
- Andean plateau (1)
- Anden (1)
- Andes (1)
- Anthropocene (1)
- Antibiotikaresistenz (1)
- Aphanizomenon (1)
- Ar-39 (1)
- Ar-40 (1)
- Aragonite (1)
- Arctic (1)
- Arctic Russia (1)
- Arctic climate change (1)
- Arktis (1)
- Bakterien (1)
- Balanced cross section (1)
- Baltic Sea coast (1)
- Billefjorden trough (1)
- Biodiversität (1)
- Biogeowissenschaften (1)
- Biomarker (1)
- Body waves (1)
- Boundary element method (1)
- Bruchmechanik (1)
- Bushveld Complex (1)
- Caimancito oil field (1)
- Caimancito-Ölfeld (1)
- Campo petrolero Caimancito (1)
- Central Asia (1)
- Chirete (1)
- Cinética de fases (1)
- Cinética del querógeno (1)
- Computational seismology (1)
- Contamination (1)
- Corundum (1)
- Cretaceous basin (1)
- Crystal nucleation (1)
- Cuenca Cretácica (1)
- Cuenca intramontana (1)
- Cuesta de la chilca (1)
- Cyanobium (1)
- Cyclostratigraphy (1)
- Dam engineering (1)
- Dead Sea (1)
- Dead Sea deep drilling project (1)
- Deformación cuaternaria (1)
- Deformation (1)
- Deuterium Exzesses (1)
- Diaguita (1)
- Dichtemodellierung (1)
- Digital geology (1)
- Digitale Gesteinsphysik (1)
- Dissolution collapse breccia (1)
- Drucklösungsprozesse (1)
- Duplex (1)
- Dynamic bulk modulus (1)
- Décollement (1)
- EPS (1)
- EXAFS (1)
- Earthquake dynamics (1)
- Earthquake forecasting (1)
- Earthquakes (1)
- East African Rift (1)
- Eastern Mediterranean (1)
- Einengungsraten (1)
- Elastic response (1)
- Elastische Gesteinseigenschaften (1)
- Energy and society (1)
- Equant (stiff) pores (1)
- Erdbeben (1)
- Erdbebenvorhersage (1)
- Erdbeobachtung (1)
- Europe (1)
- Experimental (1)
- Experimental petrology (1)
- Extracellular polymeric substances (1)
- Famatinian (1)
- Fernerkundung (1)
- Fluid (1)
- Fluid-Gesteinswechselwirkungen (1)
- Fluide (1)
- Fluidströmung (1)
- Flüsse (1)
- Fold and thrust belt (1)
- Formación Yacoraite (1)
- Fortet member (1)
- Fracture mechanics (1)
- Fracture sealing (1)
- Fracture wall offset (1)
- GDGT (1)
- Gasgeochemie (1)
- Geochemical indices (1)
- Geochemical modelling (1)
- Geochemistry (1)
- Geodynamics (1)
- Geology (1)
- Geomorphologie (1)
- Geomorphology (1)
- Geophysics (1)
- Geothermal (1)
- Geothermal monitoring (1)
- Geothermisches Monitoring (1)
- Geothermobarometry (1)
- Glaciers (1)
- Global earthquake data (1)
- Globale Erdbebenkatalogdaten (1)
- Gläser (1)
- Granite (1)
- Gravity (1)
- Grundwasser-Oberflächenwasser-Interaktion (1)
- HYPE model (1)
- Heavy metals (1)
- Hierarchical clustering (1)
- High-pressure (1)
- High-temperature experiments (1)
- Himalaya (1)
- Hochdruck (1)
- Holocene (1)
- Hydraulic aperture (1)
- Hydro-meteorological indices (1)
- Hämolyse (1)
- IHPV (1)
- Induced seismicity (1)
- Interseismic strain rates (1)
- Interseismiche Dehnungsraten (1)
- Intramontane basin (1)
- Intramontanes Becken (1)
- Inverse theory (1)
- Joint inversion (1)
- Karbonatschmelze (1)
- Kenia (1)
- Kenya (1)
- Kenya Rift (1)
- Kerogenkinetik (1)
- Kinematics of crustal and mantle deformation (1)
- Klimawandel (1)
- Krankheitserreger (1)
- Kreidebecken (1)
- Kurpsai dam (1)
- LGM (1)
- Lacustrine carbonate (1)
- Lake Issyk‐ Kul (1)
- Lake Lisan (1)
- Lake-surfaces variability (1)
- Landfill (1)
- Landslide inventory (1)
- Landslide susceptibility (1)
- Late Holocene (1)
- Leones Glacier (1)
- Levant climate (1)
- Lithospheric strength (1)
- Lithosphärenfestigkeit (1)
- Logistic regression (1)
- Lower crust (1)
- MATLAB (1)
- MC-ICP-MS (1)
- Marmarameer (1)
- Martinez del Tineo (1)
- Matrix diffusion (1)
- Mechanical aperture (1)
- Mechanical properties (1)
- Melainabacteria (1)
- Melilitit (1)
- Merensky Reef (1)
- Metastability (1)
- Methylheptadecanes (1)
- Micro-structure (1)
- Mikro-CT (1)
- Minor (1)
- Model (1)
- Modell (1)
- Moment tensor inversion (1)
- Momententensorinversion (1)
- Monsoonal variability (1)
- Mont Terri (1)
- Multivariate statistical analysis (1)
- Nanolayers (1)
- Nanorocks (1)
- Narrow (1)
- Neogene (1)
- Neotektonik (1)
- Neural networks (1)
- Nitrate-N (1)
- Nordanatolische Störungszone (1)
- Normal (1)
- North (1)
- North Anatolian Fault Zone (1)
- North Atlantic climate change (1)
- Northern Patagonian Icefield (1)
- Numerische Modellierung (1)
- Operational and environmental effects (1)
- Orbital forcing (1)
- Organofazies (1)
- Ostafrikanisches Rift (1)
- Ostseeküste (1)
- P-waves (1)
- PGE (1)
- PGM (1)
- PT path (1)
- Paleoclimate dynamics (1)
- Paleoclimatic dynamics (1)
- Paleohydrology (1)
- Paleolimnology (1)
- Paläohydrologie (1)
- Paläoökologie (1)
- Panasqueira (1)
- Passive Kontinentalränder (1)
- Passive margins (1)
- Peridotitic melts (1)
- Permafrost-Taustörungen (1)
- Permafrostlandschaften (1)
- Permeabilität (1)
- Permeabilitätsentwicklung (1)
- PhaseKinetics (1)
- Phasenkinetik (1)
- Phosphorus (1)
- Piedmont Zone (1)
- Pilze (1)
- Pitzer (1)
- Planktothrix (1)
- Plate tectonics (1)
- Plio-Pleistocene timeframe (1)
- Plio-Pleistozän Zeitfenster (1)
- Pollen (1)
- Pollenproduktivitätsschätzungen (1)
- Porous sandstone (1)
- Porphyrische Kupferlagerstätte (1)
- Poshtuk (1)
- Precambrain (1)
- Precipitation variability (1)
- Probability distributions (1)
- Quartz (1)
- Quartäre Deformation (1)
- Quaternary deformation (1)
- REVEALS (1)
- Ramos X-11 (1)
- Randelementmethode (1)
- Raoult's law (1)
- Reactive transport (1)
- Regional forcings (1)
- Reifegradbezogene Biomarker (1)
- Remote Sensing (1)
- Remote sensing (1)
- Rheological modeling (1)
- Rheologische Modellierung (1)
- Rheology (1)
- Rheology: crust and (1)
- Risk assessment (1)
- Riss (1)
- Río Pescado (1)
- S-waves (1)
- Salt Range (1)
- Salta basin (1)
- Salta-Becken (1)
- Sandstein (1)
- Savannen-Ökologie (1)
- Schwerkraft (1)
- Sea of Marmara (1)
- Seismic attenuation (1)
- Seismic cycle (1)
- Seismic noise (1)
- Seismotektonik (1)
- Self-propping fracture (1)
- Sericytochromatia (1)
- Shan (1)
- Shortening rates (1)
- Siberia (1)
- Sierras Pampeanas Orientales (1)
- Silikatschmelze (1)
- Site effects (1)
- Slope (1)
- Snow-cover (1)
- Snowella (1)
- Soil contamination (1)
- Source longevity (1)
- South American Monsoon (1)
- South Korea (1)
- Southern Kyrgyzstan (1)
- Space geodetic surveys (1)
- Spectral analysis (1)
- Spektroskopie (1)
- Static bulk modulus (1)
- Statistical seismology (1)
- Statistische Seismologie (1)
- Strahlung und chemische Eigenschaften (1)
- Strain (1)
- Strong-motion (1)
- Structural health monitoring (1)
- Strukturgeologie (1)
- Strukturmodellierung (1)
- Sturmhochwasser (1)
- Superconducting gravimetry (1)
- Supraleit-Gravimetrie (1)
- Surface roughness (1)
- Svalbard (1)
- Syn-rift breccia (1)
- Synthetische Sandsteine (1)
- System (1)
- Tasas de acortamiento (1)
- Tectonics (1)
- Tektonik (1)
- Thermal (1)
- Thermal modeling (1)
- Thermal treatment (1)
- Thermisch (1)
- Thermische Modellierung (1)
- Thermotoleranz (1)
- Tian (1)
- Time series analysis (1)
- Tungsten–tin deposits (1)
- UV fs laser ablation (1)
- Uk’37 (1)
- Unloading (1)
- Upper Indus Basin (1)
- Upper Paleozoic (1)
- Verdichtung (1)
- Versalzung (1)
- Virulenz (1)
- Volatiles (1)
- Volcanology (1)
- Wave propagation (1)
- Wave scattering and diffraction (1)
- Waveform inversion (1)
- Western Alps (1)
- XANES (1)
- XAS (1)
- Yacoraite Formation (1)
- ZHe tracer thermochronology (1)
- Zeitreihenanalyse (1)
- Zeitserie (1)
- Zustands-Übergangs-Modelle (1)
- Zyklostratigraphie (1)
- adaptation (1)
- age modeling (1)
- age-related biomarkers (1)
- algorithms (1)
- alteration geochemistry (1)
- amplicon sequencing (1)
- analog experiment (1)
- analysis (1)
- antibiotic resistance (1)
- antimicrobial resistance (1)
- archetypical gauging station (1)
- arctic (1)
- arctic water bodies (1)
- arktische Klimaänderung (1)
- asymmetric rifting (1)
- attributes (1)
- automated monitoring (1)
- bacteria (1)
- basin analysis (1)
- biodegradación (1)
- biodegradation (1)
- biodiversity (1)
- biogeoscience (1)
- biologischer Abbau (1)
- biomarcadores diagnósticos de edad (1)
- biomarcadores diagnósticos de madurez (1)
- biomarker (1)
- body waves (1)
- broadband seismometer (1)
- bubble trap (1)
- calderas (1)
- carbon stabilization (1)
- carbonate melt (1)
- carnallite (1)
- case study (1)
- cementation (1)
- change detection (1)
- chloritoid stability (1)
- climate-change mitigation (1)
- climate-change policy (1)
- coexisting phases (1)
- components (1)
- compression (1)
- continental rifts (1)
- convection (1)
- convolutional neural network (1)
- core-shell (1)
- cyanobacteria sedimentation (1)
- d-excess (1)
- damage assessment (1)
- debris flows (1)
- deep learning (1)
- deformation (1)
- density modeling (1)
- density-driven (1)
- density-driven flow (1)
- diffusion (1)
- digital core reconstruction (1)
- digital grain sizing (1)
- digital rock physics (1)
- dike (1)
- dike propagation (1)
- directivity (1)
- downstream fining (1)
- dryland (1)
- earthquake ground motions (1)
- earthquake hazards (1)
- earthquakes (1)
- ecological succession (1)
- elastic waves (1)
- electromagnetic (1)
- emergency (1)
- emergency preparedness (1)
- energy transfer (1)
- environmental reconstruction (1)
- equations (1)
- erosion (1)
- eruptions (1)
- eruptive cycle (1)
- exhumation (1)
- extracellular DNA (1)
- facies (1)
- faltendes neuronales Netzwerk (1)
- fault bend fold (1)
- flood events (1)
- flood risk management (1)
- fluid flow (1)
- fluid-rock interactions (1)
- fluvial geomorphology (1)
- formation damage (1)
- fracture growth (1)
- fracturing (1)
- freeze-thaw cycling (1)
- frost‐ cracking (1)
- full (1)
- fungi (1)
- fuzzy logic (1)
- gas geochemistry (1)
- gas supply conditions (1)
- geodynamics (1)
- geologic hazards (1)
- geological hyperspectral image classification (1)
- geologische hyperspektrale Bildklassifikation (1)
- geomorphology (1)
- geothermal energy (1)
- geothermal exploration (1)
- geothermal monitoring (1)
- geothermische Exploration (1)
- geothermische Überwachung (1)
- geyser (1)
- glacial (1)
- glacial erosion (1)
- glasses (1)
- grain (1)
- grain-size distribution (1)
- ground-penetrating radar (1)
- groundwater-surface water (1)
- hallow offshore (1)
- hemolysis (1)
- high pressure (1)
- high temperature (1)
- high-pressure (1)
- holocene (1)
- hydrate formation process (1)
- hydraulic (1)
- hydraulic fracturing (1)
- hydro-geological system (1)
- hydrothermal systems (1)
- hyperspectral (1)
- hyperspektral (1)
- imaging spectroscopy (1)
- in (1)
- induced seismicity (1)
- inheritance (1)
- injections (1)
- injectivity (1)
- interaction (1)
- internal validation (1)
- interpretation (1)
- intracellular DNA (1)
- kerogen kinetics (1)
- lake stratification (1)
- laminography (1)
- landsat (1)
- lanthanides (1)
- lanthanoid migration (1)
- lithobiont (1)
- lithosphere (1)
- local structure (1)
- location (1)
- lokale Struktur (1)
- machine learning (1)
- magma ocean (1)
- magmatic-hydrothermal systems (1)
- magnetostratigraphy (1)
- manaderos de petróleo (1)
- matríz mineral (1)
- maturity-related biomarkers (1)
- melilitite (1)
- meta-ophiolites (1)
- meta-pelites (1)
- metabarcoding (1)
- micro-CT (1)
- micro-CT scan (1)
- mine face mapping (1)
- mineral matrix (1)
- mineralische Matrix (1)
- mixed gas hydrates (1)
- modeling (1)
- modelling (1)
- moment tensor (1)
- monsunale Variabilität (1)
- multi-frequency (1)
- multi-spectral analysis (1)
- multivariate Statistik (1)
- multivariate statistics (1)
- multi‐ temporal analyses (1)
- n-alkane (1)
- n-alkanes (1)
- natural hazards (1)
- nature-based solutions (NBS) (1)
- natürlichen Ölaustritten (1)
- neotectonics (1)
- neutron imaging (1)
- nordatlantische Klimaänderung (1)
- northern high latitudes (1)
- numerical (1)
- numerical model (1)
- nördliche hohe Breitengrade (1)
- oberflächennahe Geophysík (1)
- offener Tagebau (1)
- oil seeps (1)
- open pit mining (1)
- organofacies (1)
- paleoecology (1)
- paleohydrology (1)
- pathogens (1)
- pebblecounts (1)
- permafrost landscapes (1)
- permafrost lowlands (1)
- permafrost thaw (1)
- permafrost thaw disturbances (1)
- permeability (1)
- permeability evolution (1)
- permeability-porosity relationship (1)
- phreeqc (1)
- phylogenetic and taxonomic plant diversity (1)
- picocyanobacteria diversity (1)
- pollen (1)
- pore-scale (1)
- porous media (1)
- porphyry copper deposit (1)
- pressure solution (1)
- pseudosection (1)
- psychrotolerant (1)
- radiación y propiedades químicas (1)
- radial flow (1)
- radiation and chemical properties (1)
- radiolyse (1)
- radiolysis (1)
- radiólisis (1)
- rainfall events (1)
- ramp (1)
- redox processes (1)
- relief (1)
- response (1)
- retrogressive thaw slumps (1)
- rheology (1)
- rhizosphere biogeochemistry (1)
- rift variability (1)
- rifting (1)
- rivers (1)
- rock (1)
- rock fracture (1)
- rockfalls (1)
- root activity (1)
- root-soil interaction (1)
- salinization (1)
- salt dissolution (1)
- sandstones (1)
- savanna ecology (1)
- sedaDNA (1)
- sediment production (1)
- sediment traps (1)
- sedimentary ancient DNA (1)
- sedimentary ancient DNA (sedaDNA) (1)
- sedimentology (1)
- sedimentäre alte DNA (1)
- seismic interpretation (1)
- seismic waves (1)
- seismische Interpretation (1)
- seismology (1)
- seismotectonic (1)
- sentinel-2 (1)
- shallow geophysics (1)
- shoreline movement direction (1)
- shoreline movement rate (1)
- signal-to-noise ratio (1)
- silicate melt (1)
- silicate melts (1)
- silikatische Schmelzen (1)
- simulation (1)
- site effects (1)
- situ Raman spectroscopy (1)
- size fractions (1)
- socioeconomic scenarios (1)
- solar radiation (1)
- source (1)
- spatial correlation (1)
- spectroscopy (1)
- stabilen Isotopen (1)
- stable isotope (1)
- state-transition models (1)
- storm flood (1)
- stress (1)
- stress field (1)
- structural (1)
- structural geology (1)
- structural modelling (1)
- subarctic (1)
- sulfur solubility (1)
- supergene ores (1)
- sustainability (1)
- swarms (1)
- synthetic sandstone (1)
- system architecture (1)
- tectonics (1)
- temperature (1)
- temperature extremes (1)
- thaw (1)
- thermal (1)
- thermal field (1)
- thermisches Feld (1)
- thermo-erosion (1)
- thermotolerance (1)
- tilt (1)
- topographic asymmetry (1)
- topography (1)
- tourmaline (1)
- trace elements (1)
- trajectories (1)
- treeline (1)
- tremor (1)
- uncertainty (1)
- upconversion nanoparticles (1)
- uranium speciation (1)
- vegetation cover (1)
- very high resolution imagery (1)
- virulence (1)
- volcanic earthquakes (1)
- water rock interaction (1)
- waveform (1)
- white mica (1)
- Þeistareykir Iceland (1)
- Þeistareykir Island (1)
Institute
- Institut für Geowissenschaften (143) (remove)
A tale of shifting relations
(2021)
Understanding the dynamics between the East Asian summer (EASM) and winter monsoon (EAWM) is needed to predict their variability under future global warming scenarios. Here, we investigate the relationship between EASM and EAWM as well as the mechanisms driving their variability during the last 10,000 years by stacking marine and terrestrial (non-speleothem) proxy records from the East Asian realm. This provides a regional and proxy independent signal for both monsoonal systems. The respective signal was subsequently analysed using a linear regression model. We find that the phase relationship between EASM and EAWM is not time-constant and significantly depends on orbital configuration changes. In addition, changes in the Atlantic Meridional Overturning circulation, Arctic sea-ice coverage, El Niño-Southern Oscillation and Sun Spot numbers contributed to millennial scale changes in the EASM and EAWM during the Holocene. We also argue that the bulk signal of monsoonal activity captured by the stacked non-speleothem proxy records supports the previously argued bias of speleothem climatic archives to moisture source changes and/or seasonality.
A tale of shifting relations
(2021)
Understanding the dynamics between the East Asian summer (EASM) and winter monsoon (EAWM) is needed to predict their variability under future global warming scenarios. Here, we investigate the relationship between EASM and EAWM as well as the mechanisms driving their variability during the last 10,000 years by stacking marine and terrestrial (non-speleothem) proxy records from the East Asian realm. This provides a regional and proxy independent signal for both monsoonal systems. The respective signal was subsequently analysed using a linear regression model. We find that the phase relationship between EASM and EAWM is not time-constant and significantly depends on orbital configuration changes. In addition, changes in the Atlantic Meridional Overturning circulation, Arctic sea-ice coverage, El Niño-Southern Oscillation and Sun Spot numbers contributed to millennial scale changes in the EASM and EAWM during the Holocene. We also argue that the bulk signal of monsoonal activity captured by the stacked non-speleothem proxy records supports the previously argued bias of speleothem climatic archives to moisture source changes and/or seasonality.
Geochemical processes such as mineral dissolution and precipitation alter the microstructure of rocks, and thereby affect their hydraulic and mechanical behaviour. Quantifying these property changes and considering them in reservoir simulations is essential for a sustainable utilisation of the geological subsurface. Due to the lack of alternatives, analytical methods and empirical relations are currently applied to estimate evolving hydraulic and mechanical rock properties associated with chemical reactions. However, the predictive capabilities of analytical approaches remain limited, since they assume idealised microstructures, and thus are not able to reflect property evolution for dynamic processes. Hence, aim of the present thesis is to improve the prediction of permeability and stiffness changes resulting from pore space alterations of reservoir sandstones.
A detailed representation of rock microstructure, including the morphology and connectivity of pores, is essential to accurately determine physical rock properties. For that purpose, three-dimensional pore-scale models of typical reservoir sandstones, obtained from highly resolved micro-computed tomography (micro-CT), are used to numerically calculate permeability and stiffness. In order to adequately depict characteristic distributions of secondary minerals, the virtual samples are systematically altered and resulting trends among the geometric, hydraulic, and mechanical rock properties are quantified. It is demonstrated that the geochemical reaction regime controls the location of mineral precipitation within the pore space, and thereby crucially affects the permeability evolution. This emphasises the requirement of determining distinctive porosity-permeability relationships
by means of digital pore-scale models. By contrast, a substantial impact of spatial alterations patterns on the stiffness evolution of reservoir sandstones are only observed in case of certain microstructures, such as highly porous granular rocks or sandstones comprising framework-supporting cementations. In order to construct synthetic granular samples a process-based approach is proposed including grain deposition and diagenetic cementation. It is demonstrated that the generated samples reliably represent the microstructural complexity of natural sandstones. Thereby, general limitations of imaging techniques can be overcome and various realisations of granular rocks can be flexibly produced. These can be further altered by virtual experiments, offering a fast and cost-effective way to examine the impact of precipitation, dissolution or fracturing on various petrophysical correlations.
The presented research work provides methodological principles to quantify trends in permeability and stiffness resulting from geochemical processes. The calculated physical property relations are directly linked to pore-scale alterations, and thus have a higher accuracy than commonly applied analytical approaches. This will considerably improve the predictive capabilities of reservoir models, and is further relevant to assess and reduce potential risks, such as productivity or injectivity losses as well as reservoir compaction or fault reactivation. Hence, the proposed method is of paramount importance for a wide range of natural and engineered subsurface applications, including geothermal energy systems, hydrocarbon reservoirs, CO2 and energy storage as well as hydrothermal deposit exploration.
Rheology describes the flow of matter under the influence of stress, and - related to solids- it investigates how solids subjected to stresses deform. As the deformation of the Earth’s outer layers, the lithosphere and the crust, is a major focus of rheological studies, rheology in the geosciences describes how strain evolves in rocks of variable composition and temperature under tectonic stresses. It is here where deformation processes shape the form of ocean basins and mountain belts that ultimately result from the complex interplay between lithospheric plate motion and the susceptibility of rocks to the influence of plate-tectonic forces. A rigorous study of the strength of the lithosphere and deformation phenomena thus requires in-depth studies of the rheological characteristics of the involved materials and the temporal framework of deformation processes.
This dissertation aims at analyzing the influence of the physical configuration of the lithosphere on the present-day thermal field and the overall rheological characteristics of the lithosphere to better understand variable expressions in the formation of passive continental margins and the behavior of strike-slip fault zones. The main methodological approach chosen is to estimate the present-day thermal field and the strength of the lithosphere by 3-D numerical modeling. The distribution of rock properties is provided by 3-D structural models, which are used as the basis for the thermal and rheological modeling. The structural models are based on geophysical and geological data integration, additionally constrained by 3-D density modeling. More specifically, to decipher the thermal and rheological characteristics of the lithosphere in both oceanic and continental domains, sedimentary basins in the Sea of Marmara (continental transform setting), the SW African passive margin (old oceanic crust), and the Norwegian passive margin (young oceanic crust) were selected for this study.
The Sea of Marmara, in northwestern Turkey, is located where the dextral North Anatolian Fault zone (NAFZ) accommodates the westward escape of the Anatolian Plate toward the Aegean. Geophysical observations indicate that the crust is heterogeneous beneath the Marmara basin, but a detailed characterization of the lateral crustal heterogeneities is presented for the first time in this study. Here, I use different gravity datasets and the general non-uniqueness in potential field modeling, to propose three possible end-member scenarios of crustal configuration. The models suggest that pronounced gravitational anomalies in the basin originate from significant density heterogeneities within the crust. The rheological modeling reveals that associated variations in lithospheric strength control the mechanical segmentation of the NAFZ. Importantly, a strong crust that is mechanically coupled to the upper mantle spatially correlates with aseismic patches where the fault bends and changes its strike in response to the presence of high-density lower crustal bodies. Between the bends, mechanically weaker crustal domains that are decoupled from the mantle are characterized by creep.
For the passive margins of SW Africa and Norway, two previously published 3-D conductive and lithospheric-scale thermal models were analyzed. These 3-D models differentiate various sedimentary, crustal, and mantle units and integrate different geophysical data, such as seismic observations and the gravity field. Here, the rheological modeling suggests that the present-day lithospheric strength across the oceanic domain is ultimately affected by the age and past thermal and tectonic processes as well as the depth of the thermal lithosphere-asthenosphere boundary, while the configuration of the crystalline crust dominantly controls the rheological behavior of the lithosphere beneath the continental domains of both passive margins.
The thermal and rheological models show that the variations of lithospheric strength are fundamentally influenced by the temperature distribution within the lithosphere. Moreover, as the composition of the lithosphere significantly influences the present-day thermal field, it therefore also affects the rheological characteristics of the lithosphere. Overall my studies add to our understanding of regional tectonic deformation processes and the long-term behavior of sedimentary basins; they confirm other analyses that have pointed out that crustal heterogeneities in the continents result in diverse lithospheric thermal characteristics, which in turn results in higher complexity and variations of rheological behavior compared to oceanic domains with a thinner, more homogeneous crust.
Fluids in the Earth's crust can move by creating and flowing through fractures, in a process called `hydraulic fracturing’. The tip-line of such fluid-filled fractures grows at locations where stress is larger than the strength of the rock. Where the tip stress vanishes, the fracture closes and the fluid-front retreats. If stress gradients exist on the fracture's walls, induced by fluid/rock density contrasts or topographic stresses, this results in an asymmetric shape and growth of the fracture, allowing for the contained batch of fluid to propagate through the crust.
The state-of-the-art analytical and numerical methods to simulate fluid-filled fracture propagation are two-dimensional (2D). In this work I extend these to three dimensions (3D). In my analytical method, I approximate the propagating 3D fracture as a penny-shaped crack that is influenced by both an internal pressure and stress gradients. In addition, I develop a numerical method to model propagation where curved fractures can be simulated as a mesh of triangular dislocations, with the displacement of faces computed using the displacement discontinuity method. I devise a rapid technique to approximate stress intensity and use this to calculate the advance of the tip-line. My 3D models can be applied to arbitrary stresses, topographic and crack shapes, whilst retaining short computation times.
I cross-validate my analytical and numerical methods and apply them to various natural and man-made settings, to gain additional insights into the movements of hydraulic fractures such as magmatic dikes and fluid injections in rock. In particular, I calculate the `volumetric tipping point’, which once exceeded allows a fluid-filled fracture to propagate in a `self-sustaining’ manner. I discuss implications this has for hydro-fracturing in industrial operations. I also present two studies combining physical models that define fluid-filled fracture trajectories and Bayesian statistical techniques. In these studies I show that the stress history of the volcanic edifice defines the location of eruptive vents at volcanoes. Retrieval of the ratio between topographic to remote stresses allows for forecasting of probable future vent locations. Finally, I address the mechanics of 3D propagating dykes and sills in volcanic regions. I focus on Sierra Negra volcano in the Gal\'apagos islands, where in 2018, a large sill propagated with an extremely curved trajectory. Using a 3D analysis, I find that shallow horizontal intrusions are highly sensitive to topographic and buoyancy stress gradients, as well as the effects of the free surface.
Transient permeability in porous and fractured sandstones mediated by fluid-rock interactions
(2021)
Understanding the fluid transport properties of subsurface rocks is essential for a large number of geotechnical applications, such as hydrocarbon (oil/gas) exploitation, geological storage (CO2/fluids), and geothermal reservoir utilization. To date, the hydromechanically-dependent fluid flow patterns in porous media and single macroscopic rock fractures have received numerous investigations and are relatively well understood. In contrast, fluid-rock interactions, which may permanently affect rock permeability by reshaping the structure and changing connectivity of pore throats or fracture apertures, need to be further elaborated. This is of significant importance for improving the knowledge of the long-term evolution of rock transport properties and evaluating a reservoir’ sustainability. The thesis focuses on geothermal energy utilization, e.g., seasonal heat storage in aquifers and enhanced geothermal systems, where single fluid flow in porous rocks and rock fracture networks under various pressure and temperature conditions dominates.
In this experimental study, outcrop samples (i.e., Flechtinger sandstone, an illite-bearing Lower Permian rock, and Fontainebleau sandstone, consisting of pure quartz) were used for flow-through experiments under simulated hydrothermal conditions. The themes of the thesis are (1) the investigation of clay particle migration in intact Flechtinger sandstone and the coincident permeability damage upon cyclic temperature and fluid salinity variations; (2) the determination of hydro-mechanical properties of self-propping fractures in Flechtinger and Fontainebleau sandstones with different fracture features and contrasting mechanical properties; and (3) the investigation of the time-dependent fracture aperture evolution of Fontainebleau sandstone induced by fluid-rock interactions (i.e., predominantly pressure solution). Overall, the thesis aims to unravel the mechanisms of the instantaneous reduction (i.e., direct responses to thermo-hydro-mechanical-chemical (THMC) conditions) and progressively-cumulative changes (i.e., time-dependence) of rock transport properties.
Permeability of intact Flechtinger sandstone samples was measured under each constant condition, where temperature (room temperature up to 145 °C) and fluid salinity (NaCl: 0 ~ 2 mol/l) were stepwise changed. Mercury intrusion porosimetry (MIP), electron microprobe analysis (EMPA), and scanning electron microscopy (SEM) were performed to investigate the changes of local porosity, microstructures, and clay element contents before and after the experiments. The results indicate that the permeability of illite-bearing Flechtinger sandstones will be impaired by heating and exposure to low salinity pore fluids. The chemically induced permeability variations prove to be path-dependent concerning the applied succession of fluid salinity changes. The permeability decay induced by a temperature increase and a fluid salinity reduction operates by relatively independent mechanisms, i.e., thermo-mechanical and thermo-chemical effects.
Further, the hydro-mechanical investigations of single macroscopic fractures (aligned, mismatched tensile fractures, and smooth saw-cut fractures) illustrate that a relative fracture wall offset could significantly increase fracture aperture and permeability, but the degree of increase depends on fracture surface roughness. X-ray computed tomography (CT) demonstrates that the contact area ratio after the pressure cycles is inversely correlated to the fracture offset. Moreover, rock mechanical properties, determining the strength of contact asperities, are crucial so that relatively harder rock (i.e., Fontainebleau sandstone) would have a higher self-propping potential for sustainable permeability during pressurization. This implies that self-propping rough fractures with a sufficient displacement are efficient pathways for fluid flow if the rock matrix is mechanically strong.
Finally, two long-term flow-through experiments with Fontainebleau sandstone samples containing single fractures were conducted with an intermittent flow (~140 days) and continuous flow (~120 days), respectively. Permeability and fluid element concentrations were measured throughout the experiments. Permeability reduction occurred at the beginning stage when the stress was applied, while it converged at later stages, even under stressed conditions. Fluid chemistry and microstructure observations demonstrate that pressure solution governs the long-term fracture aperture deformation, with remarkable effects of the pore fluid (Si) concentration and the structure of contact grain boundaries. The retardation and the cessation of rock fracture deformation are mainly induced by the contact stress decrease due to contact area enlargement and a dissolved mass accumulation within the contact boundaries. This work implies that fracture closure under constant (pressure/stress and temperature) conditions is likely a spontaneous process, especially at the beginning stage after pressurization when the contact area is relatively small. In contrast, a contact area growth yields changes of fracture closure behavior due to the evolution of contact boundaries and concurrent changes in their diffusive properties. Fracture aperture and thus permeability will likely be sustainable in the long term if no other processes (e.g., mineral precipitations in the open void space) occur.
One third of the world's population lives in areas where earthquakes causing at least slight damage are frequently expected. Thus, the development and testing of global seismicity models is essential to improving seismic hazard estimates and earthquake-preparedness protocols for effective disaster-risk mitigation. Currently, the availability and quality of geodetic data along plate-boundary regions provides the opportunity to construct global models of plate motion and strain rate, which can be translated into global maps of forecasted seismicity. Moreover, the broad coverage of existing earthquake catalogs facilitates in present-day the calibration and testing of global seismicity models. As a result, modern global seismicity models can integrate two independent factors necessary for physics-based, long-term earthquake forecasting, namely interseismic crustal strain accumulation and sudden lithospheric stress release.
In this dissertation, I present the construction of and testing results for two global ensemble seismicity models, aimed at providing mean rates of shallow (0-70 km) earthquake activity for seismic hazard assessment. These models depend on the Subduction Megathrust Earthquake Rate Forecast (SMERF2), a stationary seismicity approach for subduction zones, based on the conservation of moment principle and the use of regional "geodesy-to-seismicity" parameters, such as corner magnitudes, seismogenic thicknesses and subduction dip angles. Specifically, this interface-earthquake model combines geodetic strain rates with instrumentally-recorded seismicity to compute long-term rates of seismic and geodetic moment. Based on this, I derive analytical solutions for seismic coupling and earthquake activity, which provide this earthquake model with the initial abilities to properly forecast interface seismicity. Then, I integrate SMERF2 interface-seismicity estimates with earthquake computations in non-subduction zones provided by the Seismic Hazard Inferred From Tectonics based on the second iteration of the Global Strain Rate Map seismicity approach to construct the global Tectonic Earthquake Activity Model (TEAM). Thus, TEAM is designed to reduce number, and potentially spatial, earthquake inconsistencies of its predecessor tectonic earthquake model during the 2015-2017 period. Also, I combine this new geodetic-based earthquake approach with a global smoothed-seismicity model to create the World Hybrid Earthquake Estimates based on Likelihood scores (WHEEL) model. This updated hybrid model serves as an alternative earthquake-rate approach to the Global Earthquake Activity Rate model for forecasting long-term rates of shallow seismicity everywhere on Earth.
Global seismicity models provide scientific hypotheses about when and where earthquakes may occur, and how big they might be. Nonetheless, the veracity of these hypotheses can only be either confirmed or rejected after prospective forecast evaluation. Therefore, I finally test the consistency and relative performance of these global seismicity models with independent observations recorded during the 2014-2019 pseudo-prospective evaluation period. As a result, hybrid earthquake models based on both geodesy and seismicity are the most informative seismicity models during the testing time frame, as they obtain higher information scores than their constituent model components. These results support the combination of interseismic strain measurements with earthquake-catalog data for improved seismicity modeling. However, further prospective evaluations are required to more accurately describe the capacities of these global ensemble seismicity models to forecast longer-term earthquake activity.
The Central Andes region in South America is characterized by a complex and heterogeneous deformation system. Recorded seismic activity and mapped neotectonic structures indicate that most of the intraplate deformation is located along the margins of the orogen, in the transitions to the foreland and the forearc. Furthermore, the actively deforming provinces of the foreland exhibit distinct deformation styles that vary along strike, as well as characteristic distributions of seismicity with depth. The style of deformation transitions from thin-skinned in the north to thick-skinned in the south, and the thickness of the seismogenic layer increases to the south. Based on geological/geophysical observations and numerical modelling, the most commonly invoked causes for the observed heterogeneity are the variations in sediment thickness and composition, the presence of inherited structures, and changes in the dip of the subducting Nazca plate. However, there are still no comprehensive investigations on the relationship between the lithospheric composition of the Central Andes, its rheological state and the observed deformation processes. The central aim of this dissertation is therefore to explore the link between the nature of the lithosphere in the region and the location of active deformation. The study of the lithospheric composition by means of independent-data integration establishes a strong base to assess the thermal and rheological state of the Central Andes and its adjacent lowlands, which alternatively provide new foundations to understand the complex deformation of the region. In this line, the general workflow of the dissertation consists in the construction of a 3D data-derived and gravity-constrained density model of the Central Andean lithosphere, followed by the simulation of the steady-state conductive thermal field and the calculation of strength distribution. Additionally, the dynamic response of the orogen-foreland system to intraplate compression is evaluated by means of 3D geodynamic modelling.
The results of the modelling approach suggest that the inherited heterogeneous composition of the lithosphere controls the present-day thermal and rheological state of the Central Andes, which in turn influence the location and depth of active deformation processes. Most of the seismic activity and neo--tectonic structures are spatially correlated to regions of modelled high strength gradients, in the transition from the felsic, hot and weak orogenic lithosphere to the more mafic, cooler and stronger lithosphere beneath the forearc and the foreland. Moreover, the results of the dynamic simulation show a strong localization of deviatoric strain rate second invariants in the same region suggesting that shortening is accommodated at the transition zones between weak and strong domains. The vertical distribution of seismic activity appears to be influenced by the rheological state of the lithosphere as well. The depth at which the frequency distribution of hypocenters starts to decrease in the different morphotectonic units correlates with the position of the modelled brittle-ductile transitions; accordingly, a fraction of the seismic activity is located within the ductile part of the crust. An exhaustive analysis shows that practically all the seismicity in the region is restricted above the 600°C isotherm, in coincidence with the upper temperature limit for brittle behavior of olivine. Therefore, the occurrence of earthquakes below the modelled brittle-ductile could be explained by the presence of strong residual mafic rocks from past tectonic events. Another potential cause of deep earthquakes is the existence of inherited shear zones in which brittle behavior is favored through a decrease in the friction coefficient. This hypothesis is particularly suitable for the broken foreland provinces of the Santa Barbara System and the Pampean Ranges, where geological studies indicate successive reactivation of structures through time. Particularly in the Santa Barbara System, the results indicate that both mafic rocks and a reduction in friction are required to account for the observed deep seismic events.
We developed an orbital tuned age model for the composite Chew Bahir sediment core, obtained from the Chew Bahir basin (CHB), southern Ethiopia. To account for the effects of sedimentation rate changes on the spectral expression of the orbital cycles we developed a new method: the Multi-band Wavelet Age modeling technique (MUBAWA). By using a Continuous Wavelet Transformation, we were able to track frequency shifts that resulted from changing sedimentation rates and thus calculated tuned age model encompassing the last 620 kyrs. The results show a good agreement with the directly dated age model that is available from the dating of volcanic ashes. Then we used the XRF data from CHB and developed a new and robust humid-arid index of east African climate during the last 620 kyrs. To disentangle the relationship of the selected elements we performed a principal component analysis (PCA). In a following step we applied a continuous wavelet transformation on the PC1, using the directly dated age model. The resulting wavelet power spectrum, unlike a normal power spectrum, displays the occurrence of cycles/frequencies in time. The results highlight that the precession cycles are most dominantly expressed under the 400 kyrs eccentricity maximum whereas weakly expressed during eccentricity minimum. This suggests that insolation is a key driver of the climatic variability observed at CHB throughout the last 620 kyrs. In addition, the prevalence of half-precession and obliquity signals was documented. The latter is attributed to the inter-tropical insolation gradient and not interpreted as an imprint of high latitudes forcing on climatic changes in the tropics. In addition, a windowed analysis of variability was used to detect changes in variance over time and showed that strong climate variability occurred especially along the transition from a dominant insolation-controlled humid climate background state towards a predominantly dry and less-insolation controlled climate. The last chapter dealt with non-linear aspects of climate changes represented by the sediments of the CHB. We use recurrence quantification analysis to detect non-linear changes within the potassium concentration of Chew Bahir sediment cores during the last 620 kyrs. The concentration of potassium in the sediments of the lake is subject to geochemical processes related to the evaporation rate of the lake water at the time of deposition. Based on recurrence analysis, two types of variabilities could be distinguished. Type 1 represents slow variations within the precession period bandwidth of 20 kyrs and a tendency towards extreme climatic events whereas type 2 represents fast, highly variable climatic transitions between wet and dry climate states. While type 1 variability is linked to eccentricity maxima, type 2 variability occurs during the 400 kyrs eccentricity minimum. The climate history presented here shows that during high eccentricity a strongly insolation-driven climate system prevailed, whereas during low eccentricity the climate was more strongly affected by short-term variability changes. The short-term environmental changes, reflected in the increased variability might have influenced the evolution, technological advances and expansion of early modern humans who lived in this region. In the Olorgesaille Basin the temporal changes in the occurrence of stone tools, which bracket the transition from Acheulean to Middle Stone Age (MSA) technologies at between 499–320 kyrs, could potentially correlate to the marked transition from a rather stable climate with less variability to a climate with increased variability in the CHB. We conclude that populations of early anatomically modern humans are more likely to have experienced climatic stress during episodes of low eccentricity, associated with dry and high variability climate conditions, which may have led to technological innovation, such as the transition from the Acheulean to the Middle Stone Age.
The Arctic environments constitute rich and dynamic ecosystems, dominated by microorganisms extremely well adapted to survive and function under severe conditions. A range of physiological adaptations allow the microbiota in these habitats to withstand low temperatures, low water and nutrient availability, high levels of UV radiation, etc. In addition, other adaptations of clear competitive nature are directed at not only surviving but thriving in these environments, by disrupting the metabolism of neighboring cells and affecting intermicrobial communication. Since Arctic microbes are bioindicators which amplify climate alterations in the environment, the Arctic region presents the opportunity to study local microbiota and carry out research about interesting, potentially virulent phenotypes that could be dispersed into other habitats around the globe as a consequence of accelerating climate change. In this context, exploration of Arctic habitats as well as descriptions of the microbes inhabiting them are abundant but microbial competitive strategies commonly associated with virulence and pathogens are rarely reported. In this project, environmental samples from the Arctic region were collected and microorganisms (bacteria and fungi) were isolated. The clinical relevance of these microorganisms was assessed by observing the following virulence markers: ability to grow at a range of temperatures, expression of antimicrobial resistance and production of hemolysins. The aim of this project is to determine the frequency and relevance of these characteristics in an effort to understand microbial adaptations in habitats threatened by climate change. The isolates obtained and described here were able to grow at a range of temperatures, in some cases more than 30 °C higher than their original isolation temperature. A considerable number of them consistently expressed compounds capable of lysing sheep and bovine erythrocytes on blood agar at different incubation temperatures. Ethanolic extracts of these bacteria were able to cause rapid and complete lysis of erythrocyte suspensions and might even be hemolytic when assayed on human blood. In silico analyses showed a variety of resistance elements, some of them novel, against natural and synthetic antimicrobial compounds. In vitro experiments against a number of antimicrobial compounds showed resistance phenotypes belonging to wild-type populations and some non-wild type which clearly denote human influence in the acquisition of antimicrobial resistance. The results of this project demonstrate the presence of virulence-associated factors expressed by microorganisms of natural, non-clinical environments. This study contains some of the first reports, to the best of our knowledge, of hemolytic microbes isolated from the Arctic region. In addition, it provides additional information about the presence and expression of intrinsic and acquired antimicrobial resistance in environmental isolates, contributing to the understanding of the evolution of relevant pathogenic species and opportunistic pathogens. Finally, this study highlights some of the potential risks associated with changes in the polar regions (habitat melting and destruction, ecosystem transition and re-colonization) as important indirect consequences of global warming and altered climatic conditions around the planet.