An Application of the Fault Rupture Model for Probabilistic Earthquake Hazard Analysis

The fault rupture model is applied to probabilistic earthquake hazard analysis of back ground seismicity. The aim of this study is introducing effects of minute source condition to the probabilistic hazard analysis. Because average ground motion derived from empirical models are only employed in the probabilistic analysis. The empirical attenuation formulae have advantage for giving ground motion characteristics with empirical uncertainties. However the uncertainties contain source dependent randomness and fluctuations caused by not only source but also path and site effects without separation. The effects can be treated separately by the fault rupture model. Applying the fault rupture model, we expect that we can estimate more natural earthquake hazard from background seismicity than estimation by empirical method. Thousands of fault rupture models are randomly generated introducing variations of strike and dip angles, fault rupture and asperity areas, stress drop, rupture velocity, rupture duration, locations of asperities and rupture starting point and so on. The fault models are generated around a target site with variable magnitudes (Mw 5.5 - 7.0) and corresponding fault lengths. Amount of earthquakes with individual magnitude is controlled by introducing b-value. Strong ground motions from the models are calculated by using stochastic Green"fs function method. Response spectra of calculated ground motions are successfully compared with those by an empirical attenuation technique especially in short period range. However, in period range longer than one second, ground motions by the fault rupture model have larger variation than those by empirical method, because of rupture directivity effect. The advantage and disadvantage for applying fault rupture model to probabilistic earthquake hazard analysis are discussed using the data base of calculated ground motions.