Contemporaneous extension and compression in the Northern Apennines from earthquake fault-plane solutions

Abstract

The Northern Apenninic arc belongs to the deformation zones surrounding the Adriatic plate, which behaves as a rigid block. It is a NE-verging fold-and-thrust belt, which developed since the Miocene with the migration of an extensional-compressional pair. Previous seismological data are roughly in agreement with this deformation picture, although the outer compressional front was not clearly defined by the few available solutions. In this work we confirm the existence of two adjacent zones of contemporaneous extension and compression in the Northern Apennines, defining the extent of these two zones and their internal deformation better than was previously done. This is accomplished through the analysis of 125 new focal mechanisms of earthquakes (2.6