Development of Ground Motion Models for Crustal and Subduction Earthquakes in Taiwan

Development of Ground Motion Models for Crustal and Subduction Earthquakes in Taiwan

A new horizontal ground motion model that includes a median model and a sigma model for crust and subduction earthquakes in Taiwan is developed in this study. A two-step maximum-likelihood approach considering the random truncation effect is developed as the regression tool to determine the model coefficients. The advantage of the proposed regression approach is that the correlation of record residuals within the same events and sites as well as the biased sampling problem can be considered simultaneously. The orientation-independent horizontal component RotD50 of spectral acceleration with a 5% damping ratio is used as the ground motion intensity measurement for developing the ground motion model. The model's applicable period range is from 0.01 s to 5 s, which covers the fundamental period of general civil structures. The ground motion model requires several predictors to describe the earthquake source(magnitude, depth of rupture plane top, focal mechanism, mainshock, and aftershock), the path from the source to the site(i.e., closest distance to the rupture plane), and the site condition(Vs30 and Z1.0). Important ground motion characteristics, such as magnitude saturation, distance saturation, geometric spreading, anelastic attenuation, linear and nonlinear site effects, are involved in the proposed ground motion model. The aleatory uncertainty of the ground motion intensity and the statistical uncertainty of the model prediction are established to capture the possible range of the ground motion intensity. The new ground motion model will be useful for conducting site-specific probability seismic hazard analysis in Taiwan.