2-D S-velocity and radial anisotropy across the Vienna Basin from nodal probabilistic ambient noise tomography

During summer 2025, we deployed 139 5-Hz geophones along a profile running from the foothills of the eastern Alps to the Danube basin. Using ambient noise interferometry, we extract Rayleigh- and Love-wave dispersion curves at short periods (0.8-5 s) and develop a high-resolution radially anisotropic shear wave velocity model of the southern Vienna basin. The isotropic shear-wave velocity model reveals the Neogene and Pre-Neogene sedimentary layers as well as the top of the crystalline basement. We also map a normal listric fault controlling the shape of the western edge of the basin. Moreover, we find that the anisotropic structure of the southern Vienna basin is bi-layered, with a slightly negative anisotropy in the upper 1-1.5 km depth and a strong and positive anisotropy at greater depths. We interpret the shallow negative anisotropy to reflect the influence of vertically oriented cracks, while the deeper positive anisotropy corresponds to the horizontal layering of sedimentary rocks.