Minimum 1-D velocity model in Southeastern Sicily (Italy) from local earthquake data: an improvement in location accuracy

The monitoring of seismic activity in Southeastern Sicily (Italy) has been recently improved by a digital seismic
network. This effort has produced a homogeneous and complete dataset which we used to define a reference 1-D
velocity model. We have inverted P- and S-wave arrival times from 51 selected local earthquakes by using several
initial velocity and layer thickness models. Then, the range of possible velocity models obtained was tested with
earthquake locations to select the best velocity model. Improvements in location accuracy by using the Minimum
1-D velocity model, with respect to the locations obtained by using the routine velocity model, were evidenced
from the reduced residuals, the smaller estimated location errors, and the increased tendency of foci to cluster. The
distribution of relocated hypocenters confirmed the lack of seismic activity in the central part of the area.