The Spectral Source Model: A Tool for Deterministic and Probabilistic Seismic Hazard Assessment

Seismic-hazard assessment at small scales requires the computation of realistic broad-band accelerograms near the sources. Methods that use only natural records are often limited because of the limited data set. Among recently developed methods for source modelling, the spectral-source model, based on the k⁻² dislocation distribution seems particularly promising as it enables computation of synthetics for any source-receiver distance and directivity configuration. The spectral model takes into account important source characteristics, such as stress drop and directivity effects predicting acceptable high-frequency levels, whatever the station location (Bernard et al., 1996b). Firstly, some tests to explain the directivity properties of the model are presented, followed by the main results of a deterministic study carried out for the 1992 Erzincan earthquake, Turkey. Finally, results of a probabilistic study in the Moyenne-Durance region (France) are used to demonstrate the ability of this method to produce seismic-hazard maps and spectra linked to a specific return period.