Design earthquakes’ map: an additional tool for engineering seismic risk analysis. Application to southern Apennines (Italy).

Abstract

Probabilistic seismic hazard analysis (PSHA) is currently the soundest basis for the evaluation of the hazard for site-specific engineering design purposes. An increasing number of building codes worldwide acknowledges the uniform hazard spectra as the reference ground motion to determine design actions on structures and to select input signals for seismic structural analysis. The new Italian seismic code requires the seismic input for nonlinear dynamic analysis to be selected on the basis of dominating events, e.g., identified via disaggregation of seismic hazard. In the present study, the design earthquakes expressed in terms of magnitude (M), distance (R) and ε, were investigated for a wide region in the southern Apennines, Italy. The hazards corresponding to peak ground acceleration and spectral acceleration at 1 second having 475-year return period were disaggregated. For each of the disaggregation variables the shapes of the joint and marginal probability density functions were studied and the first two modes of M, R and ε were extracted and mapped. The obtained results can be used as additional information to better identify the design earthquakes. Moreover, for the study area, they allow the assessment of the seismic source contribution to various frequency ranges of the design spectrum.