Advisors: Adrian Flores Orozco, Lukas Aigner

Rock glaciers are impacted by ongoing permafrost degradation in the Alps, and their instability poses growing risks to local communities and infrastructure. Monitoring the internal structure of rock glaciers is therefore of critical importance. The transient electromagnetic method (TEM) enables efficient data acquisition in rough and complex terrain. However, compared to electrical and seismic methods, its application in alpine rock glaciers has remained limited. A better understanding of the parameters controlling the TEM response in rock glacier environments can improve the interpretation of field data and assess TEM as a field method. This thesis investigates the influence of layer thickness and resistivity on the modeled TEM response expected for a rock glacier characterized by a three-layered (active layer, frozen body, bedrock) and four-layered (including a conductive sub-frozen body layer) model. A combined approach was implemented, integrating forward modeling of literature-based rock glaciers with the analysis of field data from the Äußeres Hochebenkar rock glacier (Ötztal, Austria). From the diagnostic features identified in the numerical experiments, a rule framework was established to describe the TEM response of rock glaciers. This framework was applied to categorize literature-based forward models of rock glaciers. Based on layer detectability, the models were divided into three categories representing a) fully, b) partially and c) non-detectable layer systems in the forward modeled responses. The variations observed in the modeled responses accurately reflect the respective rock glacier structures. The results highlight that resistivity contrasts between adjacent layers and layer thickness are the dominant factors influencing response behavior, with either parameter capable of compensating for the other. Critical thresholds were defined to represent practical boundary conditions under which active and frozen layer detectability can be expected in typical rock glaciersettings. These thresholds provide as a useful reference for future field applications. The classification of the Äußeres Hochebenkar (HEK) rock glacier was not feasible due to several limiting factors. These include early-time distortions caused by the current turn-off ramp and the influence of Induced Polarization (IP) effects. IP effects cause significant changes in the TEM responses that cannot be reproduced with a resistivity-only categorization. To resolve HEK’s internal structure and enable a categorization, a complementary approach combining electrical and electromagnetic methods, and spectral IP is recommended for future investigations.