Crustal seismic velocity in the Marche region (central Italy): computation of a minimum 1-D model with seismic station corrections

A 1-D velocity model for the Marche region(Central Italy) was computed by inverting P- and S-wavearrival times of local earthquakes. A total of 160 seismicevents with a minimum of ten observations, a travel timeresidual B0.8 s and an azimuthal gap lower than 180 havebeen selected. This ‘‘minimum 1-D velocity model’’ iscomplemented by station corrections, which can be used totake into account possible near-surface velocity heterogeneitiesbeneath each station. Using this new P-wavevelocity model and the program HYPOELLIPSE (Lahr1999), the selected local events were relocated. Earthquakelocations in this study are of higher quality with respect tothe original ones. The obtained minimum 1-D velocitymodel can be used to improve the routine earthquakelocations and represents a further step towards moredetailed seismotectonic studies of the area.