3-D shear-wave velocity and radial anisotropy structure of the southern Vienna Basin, Austria from transdimensional ambient noise tomography

With the accelerating global climate crisis and the ratification of the Paris Agreement in 2015, reducing our carbon footprint has become crucial, particularly in the energy sector. Geothermal energy is becoming an attractive green energy since it is baseload-capable, and highly suitable for the supply of district heating in Europe. Identifying optimal locations for deep geothermal wells is essential, but such exploration typically depends on conventional active seismic surveys, which are logistically complex and costly. The high upfront costs associated with geothermal resource exploration remain a significant barrier to the large-scale development of deep geothermal energy across Europe. This is where passive seismic methods based on ambient noise, combined with large, dense seismic nodal arrays, offer a promising solution. In Austria, the central Vienna Basin is the primary target for deep geothermal production serving the city of Vienna. Meanwhile, the southern Vienna Basin also shows potential for geothermal production for smaller cities like Wiener Neustadt in lower Austria. In Spring 2024, we deployed 181 seismic nodal sensors in two temporary deployments over an area of 400 km². We measured fundamental-mode Rayleigh and Love-wave group velocity dispersion from seismic noise correlations and employed transdimensional Bayesian tomography to invert for isotropic Rayleigh and Love group velocity maps at periods ranging from 0.8 to 3.5 s and 0.8 to 5.5 s, respectively. We then extracted Rayleigh and Love group velocity dispersion curves from the maps at all locations and jointly inverted them for shear-wave velocity and radial anisotropy as a function of depth using a transdimensional Bayesian framework. The 3-D V_SV model highlights the seismic characteristics of the Neogene basin in the southern Vienna Basin. Additionally, the 3-D shear-wave radial anisotropy model reveals several features at depth. Combined, these findings hold significant implications for early-stage geothermal exploration in the southern Vienna Basin.