PGA distributions and seismic hazard evaluations in three cities in Taiwan

This study first presents the series of peak ground acceleration (PGA) in the three major cities in Taiwan. The PGAs are back-calculated from an earthquake catalog with the use of ground motion models. The maximums of the 84th percentile (mean + one standard deviation) PGA since 1900 are 1.03, 0.36, and 0.10 g, in Taipei, Taichung, and Kaohsiung, respectively. Statistical goodness-of-fit testing shows that the series of PGA follow a double-lognormal distribution. Using the verified probability distribution, a probabilistic analysis was developed in this paper, and used to evaluate probability-based seismic hazard. Accordingly, given a PGA equal to 0.5 g, the annual exceedance probabilities are 0.56, 0.46, and 0.23 % in Taipei, Taichung, and Kaohsiung, respectively; for PGA equal to 1.0 g, the probabilities become 0.18, 0.14, and 0.09 %. As a result, this analysis indicates the city in South Taiwan is associated with relatively lower seismic hazard, compared with those in Central and North Taiwan.