Use of Stochastic Finite Fault Simulation Method for a Target Mw=5.5 event, 2016 Kumamoto foreshock (Mw=6.5) and mainshock (Mw=7.0) at ESG6 – Blind Trial Sites

AbstractIn this study, the authors aim to test practical simulations with the stochastic finite-fault method with a dynamic corner frequency for ground motion simulation at the SEVO and KUMA stations for the earthquakes listed by the ESG6 – Blind Trial Step 2 and 3 (BP2 and BP3) Working Group. The Step 2 exercise includes simulation of an Mw = 5.5 event while Step 3 involves simulation of 2016 Kumamoto foreshock (Mw = 6.5) and Kumamoto mainshock (Mw = 7.0). After validation at the reference station SEVO for Mw = 5.5 event, the ground motion at KUMA station is amplified in the frequency domain by generic site amplification factors using the site class NEHRP-D according to the Vs30 value computed on the 1D soil model established for the Step 1 result at KUMA. In Step 3, the same simulation method is used for ground motion simulation of the 2016 Kumamoto foreshock (Mw = 6.5) and mainshock (Mw = 7.0) at SEVO and KUMA stations. For both of these events, after validation at station SEVO, the hard rock ground motion at KUMA is simulated and then propagated through the 1D soil model established for KUMA, with an equivalent linear approach. The results prove that use of local earth models to model site amplifications along with well-defined source and path parameters in ground motion simulations yield accurate simulated motions.