Completed thesis projects

  • Effects and mitigation of data gaps in time-lapse joint inversion for alpine permafrost monitoring

    2026 | Varsa Vass

    M.Sc. Applied Geophysics

    Abstract

    Automated electrical resistivity monitoring is increasingly outpacing seismic refraction campaigns at alpine permafrost sites, leaving time-lapse joint inversion schemes using these datasets, with growing gaps in seismic coverage. One such scheme, time-lapse petrophysical joint inversion (TLPJI) couples resistivity and seismic data into a single space-time inverse problem and requires both datasets to be present at each timestep. This thesis removes that requirement, letting a timestep enter the joint inversion with resistivity data alone, seismic data alone, or both, and tests whether ice content can still be recovered at timesteps missing seismic coverage. Two complementary avenues are developed. The first strengthens the inversion's regularization, separating the temporal weight of air from that of water and ice, adding a spatially modulated constraint that keeps ice content coupled at full strength within the permafrost body while relaxing it within the active layer, and introducing an additional structural prior that anchors ice content to borehole temperature. The second compares petrophysical models with different conduction mechanisms to test whether alternative choices can recover ice content more reliably. The regularization avenue is validated on a synthetic freeze-thaw cycle before both avenues are applied to a six-timestep monitoring record from the Stockhorn plateau (Valais, Switzerland), three annual surveys carrying both datasets interlaced with three resistivity-only surveys. Temporal coupling proves essential to recovering plausible ice content when seismic data are missing, and a deliberately chosen combination, the best-validated petrophysical model paired with structural information independent of the geophysical data, produces an ice estimate spatially consistent with prior interpretations of the site. No tested configuration, however, yields an ice estimate whose accuracy can be independently confirmed. Sparse seismic coverage therefore does not prevent time-lapse joint inversion from producing a physically plausible estimate of ice content, but that estimate remains only as trustworthy as the modeling choices behind it.

  • Optimized three-dimensional geoelectrical imaging and geological modeling of an anhydrite-bearing zone above a road tunnel

    2026 | Marijn Beugelsdijk

    M.Sc. Applied Geophysics

    Abstract

    Swelling of anhydrite-bearing formations poses a significant challenge to tunnel engineering, as the hydration of anhydrite to gypsum can result in substantial volume increase, ground deformation and structural damage. The Markusberg Tunnel in southern Luxembourg has experienced floor uplift and lining deformation associated with these processes, yet the geometry and extent of the potentially swelling formations above the tunnel remain insufficiently constrained. This thesis investigates the use of Electrical Resistivity Tomography (ERT) to reduce this geological uncertainty through integrated two-dimensional and three-dimensional geophysical imaging. The results demonstrate that ERT provides spatially continuous information that complements borehole observations and improves the characterization of the large-scale geological framework above the Markusberg Tunnel. While the recovered resistivity distribution cannot be interpreted uniquely in terms of lithology or the presence of anhydrite-bearing formations, the combined interpretation of geological and geophysical information provides a more complete understanding of the subsurface. Furthermore, the comparison of two- and three-dimensional inversion strategies highlights the complementary strengths of both approaches, at the same time survey optimization demonstrates that comparable imaging performance can be achieved with a reduced number of strategically selected measurements. This study concludes that ERT is a valuable tool for engineering geological investigations of swelling-prone terrain when integrated with existing geological knowledge. Rather than directly identifying anhydrite-bearing formations, its principal contribution lies in improving confidence in the geological interpretation, thereby supporting future hazard assessment and infrastructure management.

  • Reflection seismic investigation of a fault zone in sedimentary rocks

    2026 | Lasse Petersen

    B.Sc. Applied Geosciences

    Abstract

    Hammer-source seismic measurements are typically interpreted using seismic refraction methods. This study investigates whether a dataset acquired near Hombourg can also be analyzed using seismic reflection methods to provide information on the subsurface structure. To this end, 49 seismograms, each comprising 48 geophone traces, were processed. Various preprocessing methods, velocity models, and migration techniques were tested and compared. Reflected waves were identified in the raw data, although they were partially obscured by ground roll, air waves, head waves, and noise. Preprocessing significantly improved the signal-to-noise ratio; however, complete suppression of interfering signals was not possible due to aliasing and overlapping frequency spectra. Velocity analysis failed to yield unambiguous results, particularly at longer travel-times. Consequently, the effectiveness of NMO correction and migration was limited. The resulting seismic reflection profile is therefore only partially interpretable. It does not provide a high-resolution image of the subsurface but rather indicates the presence of larger reflection zones within it.

  • Feasibility of induced polarization measurements for UXO detection - A synthetic 3D sensitivity study

    2026 | Junda He

    M.Sc. Georesources Management

    Abstract

    Diese Arbeit untersucht, ob Zeitbereichs-induzierte Polarisation (TDIP) ein UXO-orientiertes geophysikalisches Messdesign in einer kontrollierten synthetischen 3-D-Studie unterstützen kann. Im Mittelpunkt stehen scheinbare Aufladbarkeitsantworten UXO-ähnlicher polarisierbarer Zielkörper. Klassische Elektrodenanordnungen werden mit Simone-style current-line Geometrien verglichen. Der Workflow kombiniert vorläufige Parameterstudien, einen data-space benchmark über alle Array-Familien, target-focused Compare-R optimized survey design, exakte model-space validation und analytical fitting. Die Ergebnisse zeigen, dass Zieltiefe, Zielgröße, Hintergrundaufladbarkeit, Array-Geometrie und acquisition effort die Detektierbarkeit und Lokalisierung deutlich beeinflussen. Eine starke raw response allein reicht nicht als Designkriterium. Cost-normalized metrics und model-space validation sind notwendig, um response strength von verlässlicher Zielinformation zu trennen. Compare-R OED liefert budgetabhängige ausgewählte Designs, während DOI, PSF, recovery und analytical fitting verbleibende Lokalisierungs- und Aufladbarkeitsmehrdeutigkeiten zeigen. Die Arbeit unterstützt IP als ergänzende Methode für UXO-orientierte geophysikalische Untersuchungen. Die stärkste Rolle liegt in einem gestuften Workflow, bei dem broad screening verdächtige Bereiche eingrenzt und target-focused TDIP design die Auswahl von follow-up Messungen verbessert.

  • Erkundung einer Verwerfungszone in Sedimentgestein mittels elektrischer Widerstandstomographie

    2026 | Sebastian Schneider

    B.Sc. Applied Geosciences

    Abstract

    Ziel dieser Bachelorarbeit ist die Erkundung einer Verwerfungszone in Sedimentgestein mittels Elektrischer Widerstandstomographie (electrical resistivity tomography: ERT). Die Verwerfungszone (Burchartz u. a., 2025) liegt im Grenzgebiet Belgien-Niederlande an dem Fluss Gulp. Die Untersuchung des Gebietes ist Teil eines größeren Projekts zur geologischen und geophysikalischen Charakterisierung des Gebietes für den womöglichen Bau des Einsteinteleskop. Dazu werden drei verschiedene ERT-Profile aufgenommen und untersucht. Zwei der Profile liegen in unmittelbarer Nähe zueinander und das dritte Profil liegt circa 3,5 km weit entfernt. Die Profile wurden mit 72 Elektroden, aber mit variierendem Elektrodenabstand, entweder 2.5, 3 oder 5 m aufgenommen, wodurch sich die Längen unterscheiden: Das erste Profil ist 355 m lang, das zweite 177,5 m und das letzte ist 213 m. Gemeinsam liegen sie auf einer Störungszone, die sich über mehrere km erstreckt. Es wird erwartet, dass die Störungszone durch die ERT Profile lokalisiert werden kann und somit eine Erkundung der Zone ermöglicht wird. Die drei ERT-Profile werden dazu mit einer Kombination aus zwei verschiedenen Elektrodenkonfigurationen aufgenommen. Sowohl Dipol-Dipol- als auch Multi-Gradient-Anordnungen werden bei diesen Messungen genutzt. Die Daten werden mit pyGIMLi (Rücker u. a., 2017) untersucht und invertiert um eine Widerstandsverteilung des Profils zu erhalten. Zusätzlich wurden Sensitivitäten und Auflösungen der Messungen berechnet und verglichen.

  • Construction and characterization of an experimental tank for the demonstration of electrical resistivity tomography

    2026 | Philipp Jakobs

    B.Sc. Applied Geosciences

    Abstract

    The aim of this work was to design and characterize a modular and transparent test tank for laboratory and teaching purposes. For this purpose, a model and technical drawings were created using a CAD program. Furthermore, suitable materials were selected, the tank was manufactured, and measurements were carried out using various targets, substrates, and electrode configurations. The inversion and modeling of the data were performed using the pyGIMLi software. The most reproducible and stable results were obtained from the water-filled experiments. In these experiments, the introduced target could be clearly visualized, especially in the upper part of the tank. In experiments with sediments, water and saline solution improved the electrode coupling but altered the conductivity distribution. This made it difficult to establish reproducible conditions. Bentonite proved to be a good solution. It acted locally, produced low and uniform contact resistances, and performed well in the displacement test. Overall, the tank is suitable for demonstrating different structures. However, the results strongly depend on the substrate used, the experimental setup, and the electrode coupling.

  • Near-surface geophysical characterization of reforested areas near a freshwater reservoir using Ground Penetrating Radar and Electrical Resistivity Tomography

    2026 | Justin Küpper

    B.Sc. Georesources Management

    Abstract

    This study investigates subsurface characterization at the eastern shore of the Wiehltalsperre (Oberbergischer Kreis, Germany) using geophysical prospecting methods. The research focuses on combining Ground Penetrating Radar (GPR) with 400 MHz and 270 MHz antennas and Electrical Resistivity Tomography (ERT) to gain a clearer understanding of the soil structure. Following the processing of the GPR data, the results were correlated with the ERT data, which were acquired using dipole-dipole and multigradient configurations. Comparing both methods proved effective in reducing interpretation uncertainties. Specifically, the combination of these techniques allowed for improved resolution of small-scale discontinuities in the subsurface. Ultimately, this work provides a reliable data foundation for future geotechnical analysis in this area.

  • Joint interpretation of geoelectric and seismic measurements on a partially reforested site near a freshwater reservoir

    2026 | Ka Lung Mak

    B.Sc. Georesources Management

    Abstract

    This study investigates the near-surface subsurface structure of a partially reforested hillslope at the Wiehltalsperre. The site has been severely affected in recent years by drought-induced forest dieback and bark beetle infestation in Norway spruce monocultures, resulting in extensive reforestation measures undertaken by the Aggerverband. To characterise the subsurface conditions that may govern the spatial patterns of forest mortality, a combined geophysical investigation using Electrical Resistivity Tomography (ERT) and Seismic Refraction Tomography (SRT) was conducted along two parallel hillslope profiles. ERT data were acquired using dipole-dipole and multiple-gradient configurations on both profiles (P1 and P2), each with 72 electrodes at 1 m spacing, and inverted using the open-source software ResIPy/R2. SRT data were collected exclusively on Profile P2 using 48 geophones at 1.5 m spacing and 42 shot points. First arrivals were manually picked in ReflexW and tomographically inverted using the pyGIMLi. All ERT inversions converged to normalised RMS values close to 1.0. The SRT inversion achieved chi^2 = 0.97 with an absolute RMS of 1.2 ms. The results reveal a vertically stratified weathering profile developed over Devonian slate and greywacke of the Rhenish Massif: organic forest soil overlying clay-rich saprolite, grading downward into weathered bedrock. Regolith thickness varies along Profile P2, implying an approximately variation in subsurface water storage capacity. Joint interpretation using a four-quadrant resistivity and velocity diagnostic framework identifies moist soil zones, saturated saprolite and a significant structural contrast between the profiles. The results provide a geophysical basis for reforestation planning at the Wiehltalsperre.

  • 3D Seismic Investigations in the Einstein Telescope Context near Herbesthal, Belgium

    2025 | Jânio Luis Augusto Videira

    M.Sc. Applied Geosciences

    Abstract

    This thesis presents a comprehensive 3D seismic refraction study conducted near Herbesthal, Belgium, in the context of the Einstein Telescope (ET) project. The primary objective was to develop a detailed near-surface velocity model to inform site characterization and a systematic analysis of the data. A dense grid of 305 geophones and a vibroseis source was deployed, and first-arrival times were meticulously picked using a combination of an automated algorithm and manual quality control. The data were processed through a robust 3D refraction tomography inversion framework, yielding high-resolution images of subsurface velocity variations. Key findings include the identification of the soil depth, 2 competent layers, and velocity contrasts that have direct implications for excavation feasibility and ground stability assessments for the ET infrastructure. This study not only enhances our understanding of the local geology, but also provides essential insights for optimizing data handling in terms of attenuation of the different components and frequencies. It demonstrates the effectiveness of seismic refraction techniques in site characterization and the importance of integrating different geophysical methods for comprehensive subsurface investigations.

  • Nicht-invasive hydrogeologische Erkundung eines Standorts im Zechstein in Rheinland-Pfalz mittels elektrischer Widerstandstomographie

    2025 | Celine Laubach

    B.Sc. Georesources Management

    Abstract

    The investigation of geological subsurface structures is crucial for obtaining new insights into geological and hydrogeological information. The aim of this work was to use geophysical electrical resistivity tomography to record and interpret the subsurface structure in the area of the former airbase in Rhineland- Palatinate. For this purpose, three geoelectric resistivity profiles (ERT) were recorded and evaluated with regard to lithological differences. The evaluations show clear differences in specific electrical resistivity, indicating varying fine grain content and variable degrees of saturation in the subsurface. In addition, several fault zones and anthropogenic influences were identified. The results provide valuable information on the geological stratigraphy of the Palatinate Basin and contribute to an improved hydrogeological assessment of the area.

  • Geological Characterisation and Multi-Physical Simulations for a Representative 3D Salt-Structure for Radioactive Waste Storage in the German Zechstein Basin

    2025 | Ronia Ivan D'Souza

    M.Sc. Applied Geosciences

    Abstract

    The safe disposal of High-Level Radioactive Waste (HLW) governed by the Standortauswahlgesetz remains a critical challenge in Germany. Zechstein salt deposits are promising host formations due to their low permeability, self-sealing properties and long-term geological stability. This thesis integrates data from Zechstein structures across Germany to develop a synthetic representative three-dimensional geological model for HLW repository assessment. The model is constructed using GemPy, an open-source Python-based tool for generating 3D structural geological models that incorporate lithostratigraphic units from the Quaternary to the Rotliegend Basement, covering the entire Zechstein Basin. This model serves as the foundation for Thermal and Hydraulic (T&H) simulations in OpenGeoSys, an open-source platform for simulating thermo-hydro-mechanical-chemical (THMC) processes which enable repository performance evaluation. Geophysical methods that include electrical resistivity tomography (ERT) modelling followed by inversion are employed on these simulated outputs using pyGIMLi to assess long-term repository monitoring feasibility. Compared to single-site models, this integrated 3D approach offers accuracy and flexibility by leveraging a broader dataset. It is calibrated with reference to Gorleben's extensive subsurface data (BfS, 2007) and contributes to the implementation of the Standortauswahlgesetz. The methodology is then transferred for evaluating salt-hosted repositories in similar geological contexts globally.

  • Prozessierung und Interpretation einer 2D-Reflexionsseismik zur Charakterisierung der Umgebung des Markusbergtunnels, Luxemburg

    2025 | Dennis Zimmer

    B.Sc. Applied Geosciences

    Abstract

    Die vorliegende Arbeit untersucht die Möglichkeiten und Grenzen der oberflächennahen 2D-Reflexionsseismik zur Abbildung des Markusbergtunnels im Süden Luxemburgs. Ziel war es, die Schichtungen des Untergrundes, potenzielle Störzonen sowie die Reflexionssignaturen des Tunnelbauwerks selbst zu erfassen. Der geologische Kontext ist durch Keuper-Einheiten geprägt, die Gips- und Anhydrit führende Schichten enthalten und aufgrund möglicher Volumenzunahmen bei Hydratation ein erhebliches Risiko für Tunnelbauwerke darstellen. Für die seismischen Messungen kam eine S-Wellen-Vibratorquelle (ElViS) zum Einsatz. Entlang zweier Profile --- einer geradlinigen Fixed-Line-Geometrie und einer polygonalen Moving-Line-Geometrie --- wurden insgesamt 136 Geophonpositionen und 135 Schusspunkte realisiert. Die Datenprozessierung umfasste Kreuzkorrelation, Bandpass- und FK-Filterung, Gain-Korrekturen sowie NMO-Korrektur, Stapelung und Migration. Zur Interpretation wurden synthetische Seismiken mit NEXD 2D berechnet, die als Referenz für typische Reflexionsmuster des Tunnels dienten. Die Ergebnisse zeigen, dass im Mittwochsprofil (Fixed Line) in rund 20 m Tiefe eine schwache Reflexion detektiert werden konnte, die in ihrer Lage und Form mit der Tunneldecke übereinstimmt. Im Freitagsprofil (Moving Line) traten dagegen starke Reflexionen bei etwa 40 m Tiefe auf, deren Zuordnung zum Tunnel jedoch unsicher bleibt. Der Vergleich mit synthetischen Modellen verdeutlicht, dass Geometrieeffekte, Störsignale und heterogene Schichtungen die Abbildung wesentlich beeinflussen. Insgesamt bestätigt die Untersuchung, dass Reflexionsseismik prinzipiell zur Detektion von Tunnelstrukturen geeignet ist, ihre Aussagekraft im Gipsmergelkeuper jedoch erheblich limitiert bleibt.

  • Synthetic seismic surveys on glaciers to analyse the influence of crystal anisotropy on seismic data

    2025 | Jingyuan Ma

    M.Sc. Applied Geosciences

    Abstract

    Glaciers record important paleoclimatic and glacial dynamics information, and their study is of great importance for understanding climate change and geological history. Geophysical methods provide a more efficient alternative to costly drilling for ice core data, especially through seismic surveys for analysing elasticity and density parameters. However, Crystal Orientation Fabric (COF) in glaciers significantly affects the elasticity and density of the ice body, which in turn alters the propagation velocity of seismic waves.In this paper, we combine the simplified horizontal model with the actual glacier data model to study the effect of internal anisotropy on seismic reflection signals through seismic simulation and geostatistical analysis. A two-dimensional distribution model of glacier density is constructed from well data and ground radar data using variogram analysis and random field generation, which provides some understanding of the relationship between glacier elastic properties and seismic wave propagation.

  • Full Waveform Inversion Using a Gaussian Process Emulator

    2024 | Ghozy El Fatih

    M.Sc. Applied Geosciences

    Abstract

    Full waveform inversion (FWI) is a currently promising method for imaging rock physical parameters from seismic wave data. The general workflow is to simulate the wave propagation iteratively, until the model parameters that produce the most similar simulated data to the original one are found. However, simulation requires expensive computing resources and is a lengthy process. Various research efforts have been attempted to speed up and optimize the FWI workflow. One way is to use a surrogate model or emulator, which is done in this work. Gaussian Process (GP) is a regression method based on the combined distribution of random variables from certain kernel functions. The expected output is the mean distribution of the posterior random function and the confidence interval. The regression model from GP can be a substitute model to reduce the number of iterations and predicting the parameter selection on the simulation results. In this thesis, the parameters chosen are P- and S-wave velocity, rock density, and quality factor. The expected output is the root mean square error. The seismic wave propagation simulator was NEXD for 1-D and 2D, while for 3-D it used SPECFEM-3D Cartesian. The GP emulator used the Psimpy Python library package. The methodology and algorithms were tested using synthetic models in 1-D and 2-D to ease the trial-and-error process. Workflows that are assured to be appropriate then applied to the ultrasound lab measurement data on four different homogeneous core samples (aluminium, marble, sandstone, and polyoxymethylene) and simulated in 3-D. The results of synthetic data trials were very accurate in determining model parameters that explain the data. In the core data, the less attenuated medium shown satisfactory results, but the ones with a high attenuation experienced challenges and required more iterations.

  • Optimale Versuchsplanung für die langfristige refraktionsseismische Überwachung der aktiven Auftauschicht am Schilthorn, Schweizer Alpen

    2023 | Janna Blaume

    B.Sc. Applied Geosciences

    Note: Janna Blaume continued on a geophysical path within the IDEA League Joint Master program.

    Abstract

    In Rahmen dieser Arbeit wird die optimale Versuchsplanung für die langfristige refraktionsseismische Überwachung der aktiven Auftauschicht am Schilthorn in den Schweizer Alpen untersucht. Angewendet werden folgende Methoden: Ein analytisches Zweischichtmodell zur Bestimmung der optimalen Geophonabstände in Abhängigkeit der Zunahme der aktiven Auftauschicht sowie die Validierung der Ergebnisse durch Modellierung von synthetischen sowie Felddaten. Die Felddaten wurden von PERMOS aus den Jahren 2008- 2022 erhoben. Folgende Ergebnisse wurden generiert: Je mächtiger die ALT wird, desto niedriger ist der rrms und desto größer sind die optimalen Geophonabstände. Wenn das Schilthorn auch in Zukunft eine gute Auflösung des Permafrostes bieten soll, dann muss die Messgeometrie angepasst werden.

  • Minimum entropy constraints for 3D structurally-coupled joint inversion of near-surface geophysical data acquired at the Rockeskyller Kopf, Germany

    2023 | Anton Ziegon

    M.Sc. Applied Geophysics

    Note: Anton Ziegon was the first official GIM graduate.

    Abstract

    Geophysical methods are widely used to gather information about the subsurface as they are nonintrusive and comparably cheap during acquisition, however, the solution to the geophysical inverse problem is inherently non-unique which introduces considerable uncertainties. Therefore, independently acquired geophysical data sets can be jointly inverted to reduce ambiguities in the resulting multi-physical subsurface images. Zhdanov et al. (2022) introduce a novel cooperative inversion approach using joint minimum entropy constraints in the regularization term of the objective functionals to create more consistent multi-physical images with sharper boundaries. Here, this approach is implemented in an open-source software and its applicability on electrical resistivity tomography (ERT), seismic refraction tomography (SRT) and magnetic data is investigated. A synthetic 2D ERT and SRT data study is used to demonstrate the approach and to investigate the influence of the governing parameters. The findings showcase the advantage of the joint minimum entropy (JME) stabilizer over separate, conventional smoothness-constrained inversions. The method is then used to analyze field data from Rockeskyller Kopf, Germany. 3D ERT and magnetic data is combined and results confirm the expected volcanic diatreme structure with improved details. The multi-physical images of both methods are consistent in some regions as similar boundaries are produced in the resulting models, which have been lacking in previous studies. Because of its sensitivity to hydrologic conditions in the subsurface, observations suggest that the ERT method senses different structures than the magnetic method. However, these structures in the ERT result do not seem to be enforced on the magnetic susceptibility distribution, showcasing the flexibility of the approach. Both investigations outline the importance of a suitable parameter and reference model selection for the performance of the approach and suggest careful parameter tests prior to the joint inversion. With proper settings, the JME inversion is a promising tool for geophysical imaging, however, this thesis also lists some objectives for future studies and additional research to explore and optimize the method.

  • Imaging of active layer characteristics through quasi-3D inversion of frequency-domain electromagnetic soundings

    2022 | Marlene Thalhammer

    M.Sc. Applied Geophysics

    Note: This thesis was supervised together with Dr. Sebastian Uhlemann (Lawrence Berkeley National Lab) and conducted during Florian's time as substitute professor of the Institute for Applied Geophysics and Geothermal Energy (now Computational Geoscience, Geothermics and Reservoir Geophysics).

    Abstract

    The active layer thickness has become an important indicator in climate change research as permafrost degradation has long been documented. The thawing of permafrost causes the release of greenhouse gases accelerating Arctic warming. Monitoring and quantifying spatial and temporal changes of the active layer are challenging but crucial for reliable climate projections. Geophysical methods offer a non-invasive investigation of electrical properties and their distribution in permafrost areas, revealing phase transitions from water to ice. Subsurface electrical resistivity images can be obtained through inversion of electromagnetic data, yet are inherently ambiguous because of the ill-posed nature of the inverse problem. Since regularization methods offer the possibility to stabilize the inversion, lateral and spatial constraints are incorporated in the inversion algorithm to produce quasi-2D and quasi-3D subsurface models. The developed methodology is evaluated based on synthetic data sets to determine suitable inversion parameters, which are subsequently applied to a field example from the Seward Peninsula, Alaska. Laterally constrained inversion methods based on a fewlayer starting model succeed in resolving sharp interfaces in quasi-layered environments. In more complex settings minimum-structure models can retrieve accurate subsurface representations leveraging on vertical and horizontal smoothness constraints. Enforcing lateral and spatial consistency between neighboring soundings thereby yields a similar degree of model smoothness. The inverted field data confirms the conclusions drawn from the synthetic study, as meaningful three-layered models with regard to electrical resistivities are recovered, indicating resistive snow overlying the conductive active layer and highly resistive permafrost. However, the inversion results imply that the snow layer has a significant effect on the predicted model. The implemented constraints help in reducing the ambiguity of the models, but uncertainties introduced by limited data availability cannot be overcome. The potential of adopting spatial and lateral constraints to the inversion is shown, although it becomes evident that additional a priori information needs to be integrated in the objective function in order to comprehensively image the active layer.

  • Automated assessment of slope stability - application of machine learning to ERT monitoring data and integration with geomechanical models

    2021 | Feliks Kiszkurno

    M.Sc. Applied Geophysics

    Note: This thesis was supervised together with Dr. Sebastian Uhlemann (Lawrence Berkeley National Lab) and conducted during Florian's time as substitute professor of the Institute for Applied Geophysics and Geothermal Energy (now Computational Geoscience, Geothermics and Reservoir Geophysics).

  • Process-based geophysical imaging of permafrost degradation: Is it getting wetter or drier?

    2021 | Clara Fraile Mujica

    M.Sc. Applied Geophysics

    Note: This thesis was supervised together with Prof. Christian Hauck (University of Fribourg) and conducted during Florian's time as substitute professor of the Institute for Applied Geophysics and Geothermal Energy (now Computational Geoscience, Geothermics and Reservoir Geophysics).

  • Geoelectrical imaging of subsurface discontinuities and heterogeneities using low-dimensional parameterizations

    2021 | Aaron Förderer

    M.Sc. Applied Geosciences

    Note: This thesis was supervised together with Prof. Florian Wellmann and conducted during Florian Wagner's time as substitute professor of the Institute for Applied Geophysics and Geothermal Energy (now Computational Geoscience, Geothermics and Reservoir Geophysics).

  • Improved quantitative imaging of alpine permafrost evolution through time-lapse joint inversion of seismic refraction and electrical resistivity data

    2020 | Johanna Klahold

    M.Sc. Applied Geophysics

    Note: Johanna Klahold received the Heitfeld award for her work. This thesis was supervised together with Prof. Christian Hauck (University of Fribourg) and conducted during Florian's time as substitute professor of the Institute for Applied Geophysics and Geothermal Energy (now Computational Geoscience, Geothermics and Reservoir Geophysics).

    Abstract

    Quantitative estimation of pore fractions filled with liquid water, ice and air is one of the prerequisites in many permafrost studies and forms the basis for a process-based understanding of permafrost and the hazard potential of its degradation in the context of global warming. The volumetric ice content is however difficult to retrieve, since standard borehole temperature monitoring is unable to provide any ice content estimation. Geophysical methods offer opportunities to image distributions of permafrost constituents in a non-invasive manner. A petrophysical joint inversion was recently developed to determine volumetric water, ice, air and rock contents from seismic refraction and electrical resistivity data. This approach benefits from the complementary sensitivities of seismic and electrical data to the phase change between ice and liquid water. A remaining weak point was the unresolved petrophysical ambiguity between ice and rock matrix. Within this study, the petrophysical joint inversion approach is extended along the time axis and respective temporal constraints are introduced. If the porosity (and other time-invariant properties like pore water resistivity or Archie exponents) can be assumed invariant over the considered time period, water, ice and air contents can be estimated together with a temporally constant (but spatially variable) porosity distribution. It is hypothesized that including multiple time steps in the inverse problem increases the ratio of data and parameters and leads to a more accurate distinction between ice and rock content. Based on a synthetic example and a field data set from an Alpine permafrost site (Schilthorn, Swiss Alps) it is demonstrated that the developed time-lapse petrophysical joint inversion provides physically plausible solutions, in particular improved estimates for the volumetric fractions of ice and rock. The field application is evaluated with independent validation data including thaw depths derived from borehole temperature measurements and shows generally good agreement. As opposed to the conventional petrophysical joint inversion, its time-lapse extension succeeds in providing reasonable estimates of permafrost degradation at the Schilthorn monitoring site without a priori constraints on the porosity model, amounting to an approximate relative loss of 40% of ground ice in the upper 15m below the surface in the time period between 2008 and 2017.

  • Influence of prior data on the optimization of borehole locations for the estimation of geothermal reservoir parameters

    2020 | Julia Becker

    B.Sc. Applied Geosciences

    Note: This thesis was supervised together with Johanna Fink and conducted during Florian's time as substitute professor of the Institute for Applied Geophysics and Geothermal Energy (now Computational Geoscience, Geothermics and Reservoir Geophysics).
The list above contains completed thesis projects by our alumni. If you are looking for currently offered B.Sc. and M.Sc. topics, please have a look at this page.