SASHA: a computer program to assess seismic hazard form intensity data

The SASHA program for the estimate of seismic hazard from a probabilistic analysis of macroseismic data is presented and made freely available (together with the user guide and sample input files) upon request to the authors. The program allows the computation of typical hazard outputs (hazard curve for different intensity thresholds, intensity or PGA value characterized by a fixed exceedance probability in a given exposure time) for a generic set of sites by fully exploiting information locally available about seismic effects (intensity data) of past earthquakes. This information can be integrated with “virtual” intensity values deduced from epicentral data and macroseismic observations available at neighboring sites. Uncertainties about intensity data and the actual reliability of local seismic histories are taken into account. SASHA has been developed in the framework of a recent research project devoted to seismic hazard assessment in Italy (INGV-DPC Project S1; http://esse1.mi.ingv.it), where the program has been extensively applied. For this reason, region-dependent coefficients of the empirical relations presently implemented in the code (e.g., to compute intensity attenuation with source distance and to “convert” intensity hazard estimates to PGA) are the ones most recently proposed for the Italian territory. Relevant parameters can, however, be modified by the user to allow application to different countries.