台南地區地震危害潛勢微分區

台南地區大部分位於沖積平原上，人口密集度高，中高層建築物櫛比鱗次，且部分社區內老舊建築改建速度緩慢，鑑於至少有6條活動斷層分布本區，可見有著極高的地震災害潛勢。本研究使用自1683至1899年的11個災害性地震，1900年至2010年震矩規模大於5的淺層地震活動資料，以及三條第一類活動斷層進行台南地區地震危害潛勢的微分區。結果顯示台南地區地震危害潛勢最高區域是位於北部，主要包括後壁區、新營區、柳營區、白河區西半側、六甲區西半側、鹽水區東北側、下營區東北側、官田區北側以及麻豆區北側，10年、30年、50年期間超過MMI震度階VIII級的地震震度機率分別為40％以上、80％以上、90％以上。另外，10年期間超過MMI震度階VI級的發生機率在90％以上的區域則位於台南中北部區域。最後與現行建築物耐震設計規範及解說之台南地區震度劃分圖比較，則顯示低估了以下區域：後壁區南側、白河區西側、東山區西側、柳營區中東半側、六甲區北側以及新營區東北側之地震危害度。本研究成果可提供重要經濟建設之廠房設置耐震設計參考，將有助於減輕本區未來地震災害的損失。

關鍵字

台南地區；地震危害潛勢；微分區；震度發生機率

並列摘要

The majority of the Tainan area is a densely populated alluvial plain. Medium- and high-story buildings are increasing. Considering that at least six active faults are distributed in this area, we can foresee a very high earthquake hazard potential. In this study, a catalog of 2041 shallow earthquakes which occurred from 1900 to 2010 with Mw magnitudes ranging from 5.0 to 8.2, and 11 disastrous earthquakes which occurred from 1683-1899 as well as three active faults are used to estimate the seismic hazard potential in the Tainan area for seismic microzonation. The results reveal that the highest earthquake hazard potential in the Tainan area is located in the northern part, including Houbi Dist., Xinying Dist., Liuying Dist., western Baihe Dist., western Liujia Dist., northeastern Yanshui Dist., northeastern Xiaying Dist., northern Guantian Dist. and northern Madou Dist. The probabilities of seismic intensity exceeding MMI VIII in 10, 30, and 50-year periods in above areas are greater than 40%, 80% and 90%, respectively. Moreover, the probability of seismic intensity exceeding MMI VI in 10-year period are greater than 90% in the central and northern areas of Tainan. Finally, by comparing with the seismic zoning map of Taiwan in the current building code that was revised after the 9/21 earthquakes, we find that the classification of the whole Tainan area zone I has underestimated the following areas: southern Houbi Dist., western Baihe Dist., western Tungshan Dist., central and eastern Liuying Dist., northern Liujia Dist. and northeastern Xinying Dist.. Results of this study show a high earthquake hazard potential in the Tainan area.