Seismicity and P‐wave velocity image of the Southern Tyrrhenian subduction zone

Abstract

This paper focuses on the deep Earth structure and earthquake distribution within the Southern Tyrrhenian subduction zone. We discuss seismological observations which provide insight into the mechanics of subduction processes for an unusual compressional margin. The motivation for this work derives from the recognition that little is known about one of the most intriguing geodynamic features of the Italian Peninsula, and the fact that a large amount of information can be extracted from data collected by the Istituto Nazionale di Geofisica National Seismic Network. We show that the hypocentres of intermediate and deep earthquakes that have occurred since 1988 image a NW‐dipping plane, continuous from the Ionian Sea to the Tyrrhenian, down to 450 km depth. We also present a 3‐D model of the deep structure beneath southern Italy, derived using deep earthquake seismic tomography. Tomographic images reveal a high‐velocity body dipping from the Apulian and Iblean forelands towards the Tyrrhenian Basin in the crust and upper mantle (at least down to 320 km depth). This high‐velocity body may be related to the cold, subducted Ionian lithosphere. Earthquake hypocentres are confined within the high‐velocity body, delineating the subduction beneath the Calabrian Arc. Copyright © 1995, Wiley Blackwell. All rights reserved