The impact of 1D seismostratigraphical amplification effects on probabilistic seismic hazard maps at regional scale: the case of Tuscany (Central Italy)

Seismic risk assessment at regional scale requires hazard estimates accounting for seismostratigraphical amplification effects. When detailed data related to the local subsoil configuration are lacking, these effects can be inferred from numerical simulations fed with information available on at regional scale. A key aspect concerns the implementation of these outcomes including relevant uncertainty into probabilistic seismic hazard estimates relative to standard subsoil conditions. A coherent approach is here proposed, which coherently accounts for the inherent probabilistic character of reference hazard estimates and of uncertain 1D seismostratographical amplification effects inferred from geological maps. The proposed approach has been applied in Central Italy relative PGA values corresponding to an exceedance probability of 10% in 50y. It is shown that accounting for uncertainty affecting amplification estimates is of main importance for correct implementation into PSHA. The outcome of this analysis is not expected to be considered for anti-seismic design of single structures, which requires detailed, and sound estimates of site effects at the proper scale. Anyway, these estimates may play a role for the preliminary identification of most critical situations along lifelines or outside inhabited areas where seismic microzonation studies are not available.