| Ground motion prediction plays an important role in seismic hazard evaluation and mitigation. Among various techniques, the stochastic simulation method is a simple, powerful and widely used way to characterize the behavior of ground motions of a broad range of earthquake magnitudes and distances. By comparing the response spectra of observed and simulated ground motions, the source parameters of the earthquake, the propagation properties of the crust and the site amplification behavior may be inferred. This information allows us to better predict future ground motions and ultimately improve building codes.; In this study, the revised Finite Fault Stochastic Simulation technique proposed by Motazedian (2002) and Motazedian and Atkinson (2005) is used to model over 400 ground motion records from the 1999 MW 7.6 Chi-Chi Taiwan earthquake, at near-fault to regional distances. The geometric and anelastic attenuation properties of the crust, site amplifications and duration are empirically calculated from the recorded seismic data.; With the specified path and site model for the Chi-Chi earthquake, stochastic simulation is conducted first on rock stations for model calibration, and then on soil stations using the calibrated model. Based on comparisons of simulations and data, I conclude that the stress drop of the Chi-Chi earthquake was 40 bars, which is relatively low compared with earthquakes of similar magnitude in other regions (eg. 50-70 bars in California). Regarding site effects, I conclude that the H/V (horizontal/vertical component) ratio works well as a site amplification term, and that obvious nonlinear soil response was observed on soil stations during the Chi-Chi earthquake. Furthermore there are marked basin effects in the Taipei region for ground motion) of intermediate frequency (around 1 Hz). This could be an important contributing reason for building damage in the Taipei area during the Chi-Chi earthquake. |
