Insights into Western Sicily’s seismotectonics from recent seismicity and 1968 Belice mainshock ground motion simulations

Western Sicily, in the central Mediterranean, is part of the Apennine-Maghrebian fold-and-thrust belt. Although the region is characterised by active deformation and experienced destructive earthquakes in the past, such as those occurring in the Belice valley in 1968, inadequate data has resulted in controversial interpretations of seismic sources, hindering precise hazard assessments. By exploiting recent seismic data and field geological constraints, a consistent seismotectonic model and simulated earthquake scenarios have been developed to better understand the 1968 seismic sequence source. The study area is primarily deformed by southeast-verging thrusts extending deep into the crystalline basement. Seismic and geological data point to NE-SW oriented main structural lineaments resulting from a NW-SE shortening regime. A south-verging thrust fault system appears to be a compelling candidate for the 1968 event source; through numerical simulations, a hypothesised fault was tested to reproduce realistic ground shaking comparable to that generated by the strongest event of 1968. Findings indicate that the proposed fault model, with a moment magnitude of Mw 5.7, can accurately reflect the observed data and instrumental records.