Modeling the 1980 Irpinia earthquake by stochastic simulation. Comparison of seismic scenarios using finite-fault approaches

Abstract

To define more accurately the near field and the directivity effect, different methodologies of finite-fault modelling have been used to describe the behaviour of ground shaking based on deterministic, stochastic and hybrid stochastic-deterministic approaches as in the framework of the ongoing European project “LESSLOSS – Risk Mitigation for Earthquakes and Landslides”. In this study, we simulate and compare seismic scenarios obtained from the complex source characteristic of the 1980 Irpinia earthquake, M 6.9, Southern Italy, using models based on the source models hypothesized in Bernard and Zollo (1989) and in Valensise et al. (1990). Furthermore, two finite-fault numerical approaches are used: 1. The approach RSSIM [Carvalho et al., 2004] that is a non-stationary stochastic simulation method that synthesizes the ground motion due to an extended source; 2. The approach EXSIM [Motazedian and Atkinson, 2005] that is a new version of FINSIM [Beresnev and Atkinson, 1998] introducing a new variation based on a “dynamic corner frequency”. The shaking scenarios are computed in terms of Response Acceleration Spectra (PSA), time series, peak ground acceleration (PGA) at bedrock level. Source and path propagation parameters taken from other studies were tested and the computed shaking scenarios are compared to acceleration records to eight different stations. Preliminary results are here presented in terms of PGA maps for the Campania region (Southern Italy).