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).