Vp/Vs estimation in southwestern Europe from P-wave and surface-wave tomography analysis

For 10 regions in southwestern Europe, a comparison has been made between the surface-wave and P-wave tomography results available in the literature. Starting from the P-wave models inferred by P-wave tomography, theoretical phase velocities have been computed adjusting the radio between P-wave and S-wave velocities in order to simultaneously fit the observed Rayleigh-wave phase velocities. The Vp/Vs ratio is an important variable that can be used to investigate the nature of variations in the propagation velocity of seismic waves in the Earth's interior. More specifically. it can be used to discriminate between thermal and compositional influences on the velocities of seismic waves. In this sense, the largest value in the distribution of the Vp/Vs ratio that we have obtained in the modelling is associated with a specific region in north-central Italy where the presence of fluids at crustal level is well known.