Seismic velocity structure and seismotectonics of the southern Vienna Basin (Austria) with a large-N nodal deployment

In spring 2024, we deployed a large seismic nodal array across the southern Vienna Basin, Austria. Using a machine-learning approach, we constructed a seismic catalog for the 60-day deployment period and reliably identified 100 events. We applied a local earthquake tomography inversion procedure to relocate the detected events and derive three-dimensional P- and S-wave velocity models and V_P/V_S estimates. The results reveal a low-velocity anomaly with high V_P/V_S estimates, corresponding to the Neogene basin structure. In contrast, high-velocity anomalies with low V_P/V_S estimates highlight nappe systems associated with the Alpine Orogen. Most of the relocated seismicity during the deployment is linked to the April 14_th, 2024, M ~ 3 earthquake. The mechanism for this event, along with its aftershock distribution, suggest that the rupture occurred on a normal splay fault of the Vienna Basin Transfer Fault System, situated near its intersection with the basal detachment at depth. As this area is highlighted for its geothermal resource potential, a comprehensive understanding of geological structures and potential hazards is essential for responsible resource development.