Minor shallow gravitational component on the Mt. Vettore surface ruptures related to MW 6, 2016 Amatrice earthquake

Abstract

On 24th August 2016 a ML 6.0 earthquake occurred near Amatrice (central Italy) causing nearly 300 fatalities. The mainshock ruptured a NNW-SSE striking, WSW dipping normal fault. The earthquake produced several coseismic effects at ground, including landslides and ground ruptures. In particular, ground surveys identified a 5.2 km long continuous fracture along the Mt. Vettore flank, both on rock and slope deposits, along one of the active normal fault segments bounding the relief to the west. In this work, we evaluated the contribution of seismically-induced surface instabilities to the observed ground fractures by means of a permanent-displacement approach. The results of a parametric analysis show that the computed seismically-induced gravitational displacements (about 2-10 cm) are not enough to explain field observations, testifying to a mean 20-25cm vertical offset. Thus, the observed ground fractures are the result of primary faulting related to tectonics, combined with gravitational phenomena.