We use the LOTOS algorithm for local earthquake tomography
, which performs iterative simultaneous inversions
for P and S velocity and source parameters. The Vp/Vs values are derived
from the independent P- and S-velocities. Some authors argue that this approach provides less stable results
for Vp/Vs than direct inversion for Vp and Vp/Vs parameters. In the next
section we present arguments in favor of the first scenario based on
synthetic modelling