Microzonation of Seismic Hazards and Assessment of Potential Human Fatality in the Chianan Area, Taiwan

Abstract

The purpose of this study is to assess seismic hazards in the 57 administration districts of the Chianan area (Chiayi County, Chiayi City, and Tainan City), Taiwan, in the form of ShakeMaps, as well as to estimate potential human fatalities from scenario earthquakes on the three type I active faults in this area. The resultant ShakeMap patterns of maximum ground motion show two regions with high modified Mercalli intensity (MMI; greater than IX). One is in the Chiayi area around Minsyong, Dalin, and Meishan due to presence of the Meishan fault and large site amplification factors. The other is in the Tainan area around Jiali, Madou, Siaying, Syuejia, Jiangjyun, and Yanshuei. The projected probabilities in 10, 30, and 50 yr periods with seismic intensity exceeding MMI VIII in these areas are greater than 45%, 80%, and 95%, respectively. Furthermore, from the distribution of probabilities, high values of greater than 95% over a 10 yr period with seismic intensity corresponding to Central Weather Bureau intensity V and MMI VI are found in central and northern Chiayi and northern Tainan. Finally, from estimation of potential human fatalities for scenario earthquakes on three active faults in Chianan area, it is noted that potential fatalities increase rapidly for people above age 45. Total fatalities reach high peaks in two age groups, ages 60–64 and 75–79, respectively, from scenario earthquakes on the Meishan and Chukou faults. On the other hand, total fatalities peak at ages 55–64 in the case of Hsinhua fault; this is probably because more people in this age group live in the nearby densely populated urban areas (>5000 persons/km2) such as the Yongkang District. We urge the local and central governments to pay special attention to seismic‐hazard mitigation in this urbanized area, with its large number of old buildings. Online Material: Maps of probabilities of exceeding Central Weather Bureau intensity (CWBI) V, VI, and VII and modified Mercalli intensity (MMI) VI and VII of ground shaking over 10, 30, and 50 yr periods.