REASSESS V1.0: a computationally-efficient software for probabilistic seismic hazard analysis

A stand-alone software for the probabilistic assessment of seismic hazard is devel- oping. In its final version, it shall be structured in thre e modules for: (i) site-specific, (ii) sce- nario-based and (iii) multi-site (regional) anal yses. This paper focuses on (i), which is devoted to single-site probabilisti c seismic hazard analysis (PSHA). Seismic sources can be either z ones or individual faults. The algorithm to compute PSHA is implemented assuming, classically, that the process of occurrence of earthquakes on each seismic source follows a homogeneous Poisson pr ocess; the processes for different sources are independent. The required input data are: (1) the source(s) geometry and the annual rate(s) of occurrence of earthquakes in the magnitude interval of interest; (2) the distribution of magnitude given the occurrence of one earthquake; (3) the ground motion propagation model (GMPM); (4) the soil classification at the site for which haz ard is evaluated. Regarding (1-3), the user is aided by some library impl emented in the software. REASSESS also is able to account for model uncer tainty, in fact, logic trees can be built based on alternatives for the source’s annual ra te of earthquake occurrence, magnitude dis- tribution and GMPM. The strength of REASSESS, beyond the user-friendly interface, stays in the PSHA computation algorithms. These have been coded in MATLAB®, targeting accuracy and reduced computing time. Its potential for ea rthquake engineering and engineering seismology applications is il- lustrated by a few applications discussed in the paper.