Seismic structure of the Calabrian subduction zone

Abstract

During the last decades, many studies have been addressing the seismic structure of the crust and upper mantle beneath the Tyrrhenian-Calabrian Arc, crucial to define the deep and shallow geometry of the subducting plate and the circulation of the surrounding mantle. We present the INGV contribution to the understanding of the subduction system from a seismological point of view. We illustrate the most recent results on relocated deep seismicity,on high resolution local earthquake tomography, and on teleseismic tomography with ocean bottom seismometers data. The pattern of mantle flow is imaged by a large collection of shear-wave splitting measurements from national network and temporary deployments. The 3D geometry of the narrow (about 200 km) subducting lithosphere shows a well defined shallow bend from sub-horizontal to 70-75 NW dipping. Lithosphere dives down to 400 km depth and turns again horizontal in the transition zone. Low seismic velocity in the wedge correspond to the Tyrrhenian basin and Aeolian Arc. Focused mantle circulation is induced by the slab motion, with evidences of return flow from behind the subducted lithosphere around the south-western slab edge.