Probabilistic seismic hazard assessment in the high-risk area of south-eastern Sicily (Italy)

A probabilistic seismic hazard analysis was carried out for the SE sector of Sicily, an area characterized by the highest levels of seismic hazard in Italy and by high exposure, both in terms of cultural heritage and of critical industrial facilities. Compared to the Italian reference hazard map (MPS04), this study is based on the most updated information about regional seismic sources and ground-motion attenuation. Epistemic uncertainties associated with the input elements of the computational model were taken into account following a logic-tree approach. Special care was devoted to defining the regional source zone model by considering four alternative models that share the zones defining the boundary conditions of the study area but differ in the seismotectonic characterization of SE Sicily. Seismic hazard was assessed in terms of PGA, PGV, spectral acceleration and displacement on rock for four return periods (30, 50, 475, 975 years). A disaggregation analysis was then performed for some sites of interest. Results confirm the high hazard of the area, with expected values of PGA (at 10% probability of exceedance in 50 years) slightly higher than the reference MPS04 map. Strong differences emerge instead between the acceleration uniform hazard spectra of this study and the reference ones for the longest return periods.