P-WAVE ARRIVAL TIME INVERSION BY USING THE TAU-P METHOD - APPLICATIONTO THE MT-VESUVIUS VOLCANO, SOUTHERN ITALY

In this paper we have applied a tau - p inversion method based on a no n linear approach to a set of first P-arrival times from a 2-D active seismic experiment performed at Mt. Vesuvius in 1994. The initial seis mic investigation is devoted to the study of the shallow structure and the tau - p method has been used for modelling velocity variations of a spherically concentric medium which is a better approximation than a flat layer of the Vesuvius geometry. We are able to obtain detailed 1-D velocity models along different specified sections of the recorded seismic line. These sections span different depth ranges and indicate strong lateral and vertical P-velocity variations in the first 1 km o f the volcano structure with values ranging from about 1.5 km/s at the surface to 3.5-4.0 km/s at depth. The average 1-D concentric model ob tained in this study call be used as a reasonable starting model for i terative high-resolution tomographies of Vesuvius velocity structures.