Nonlinear P-wave tomography of subducted lithosphere beneath central-southern Apennines (Italy)

Abstract

We present new tomographic images for the Pwave velocity structure in the upper mantle beneath centralsouthern Apennines down to 510 km depth. The model is computed by nonlinear inversion of relative arrival times of both direct and secondary teleseismic phases, handpicked from over 2800 waveforms recorded by the Italian seismic network during 1988-2000. Beneath central Apennines, the images reveal a continuous, SW-dipping high-velocity body, from 150 km down to 500 km. At shallower depths, a pronounced low-velocity zone is recognized from the uppermost mantle beneath the Apenninic belt down to 200 km below the Tyrrhenian area. This feature is proposed to affect the seismic structure of the downgoing slab, weakening its velocity signature. Beneath southern Apennines, highvelocity anomalies are reconstructed in the uppermost mantle of the Apulian foreland and below the belt in the range 100 400 km. Low-velocity regions, interpreted as due to asthenospheric upwelling, are recovered above or across the fast structures, as at the southeastern end of the Apennines where a possible complete slab breako is suggested.