Study on Probabilistic Seismic Hazard Maps of Taiwan after Chi-chi Earthquake

Probabilistic seismic hazard maps are widely used for engineering design, land use planning, and disaster mitigation etc. This study conducted a review of readily available information on tectonic setting, geology, and seismicity, and the attenuation of peak ground acceleration (PGA) of Taiwan for completing the revised probabilistic seismic hazard maps by the state-of-the-art probabilistic seismic hazard analysis (PSHA) method. The mainshocks from the earthquake catalog of 1900 to 1999 were used to evaluate the earthquake recurrence rate for regional sources and subduction intraslab sources from Truncated-Exponential model. The fault-slip rates for estimating the earthquake recurrence rates of faults and subduction interface sources by Characteristic-Earthquake model were adopted. The revised PSHA in this study takes into consideration the fact that subduction plate sources induce higher ground-motion levels than crustal sources, and active faults induce the hanging-wall effect in attenuation relationships. After considering the fault activity and hanging wall effects in our revised PSHA, it was found that the peak ground acceleration (PGA) levels of near-field in Taiwan always exceed 0.4 g in a 475-year return period. This situation is clearly obvious in central Taiwan, the Miaoli Taichung region, Chyiayi Tainan region and eastern longitudinal valley.