Source analysis of the 2002 Molise, southern Italy, twin earthquakes (10/31 and 11/01)

Abstract

On October 31, 2002, a moderate size earthquake (Mw = 5.8) occurred in Molise region, southern Italy, causing loss of young human lives in a school collapse and destructions in several villages. The day after, a slightly smaller earthquake happened a few kilometers westward from the first one, without making strong damage. We use a complete set of seismological data (global, regional and local, including both body and surface waves) to better understand the source process of these two events. We show that the two earthquakes are similar, in terms of hypocentral depth, focal mechanism, and source kinematics. Moreover, the imaged slip zones are almost contiguous which makes the time delay between the two shocks (29 hours) an open question. The identified updip rupture propagation has amplified the radiation usually created by such Mw = 5.8 earthquakes at 15–20 km depth. We model a maximum acceleration zone in agreement with location of damaged villages.