Seismic-Hazard Assessment for a Characteristic Earthquake Scenario: An Integrated Probabilistic–Deterministic Method

Probabilistic seismic hazard analysis (PSHA) is classically performed through the Cornell approach by using a uniform earthquake distribution over the source area and a given magnitude range. This study aims at extending the PSHA approach to the case of a characteristic earthquake scenario associated with an active fault. The approach integrates PSHA with a high-frequency deterministic technique for the prediction of peak and spectral ground motion parameters in a characteristic earthquake. The method is based on the site-dependent evaluation of the probability of exceedance for the chosen strong-motion parameter. The latter is obtained from the statistical analysis of the synthetic waveform database produced for a large number of possible rupture histories occurring on the characteristic earthquake fault. The method has been applied to a hazard evaluation in the Umbria region, where the threat is represented by a fault having the same geometry and mechanism as the 26 September 1997, Colfiorito earthquake (central Italy; moment magnitude, Mw 6).