利用最大加速度值評估台灣西部四大都會區之耐震規範

Date
2008
Authors
陳中保
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摘要 台灣位在地震頻繁的環太平洋地震帶上,雖然台灣西部的地震發震頻率比東部低,規模強度亦稍弱於東部的地震,但是台灣西部人口密集一旦發生災害將比東部更加嚴重。本研究是利用中央氣象局,西元1994年至2005年共12年中所有超過震度4級(PGA南北方向,東西方向及上下三個方向量值的極大值為標準)的地震,對西部四大都會區(台北盆地 ,台中縣市,台南縣市,高雄縣市)影響。以四大都會區中所有測站水平加速度值(南北方向與東西方向PGA值平方和開根號)與行政院修正核定之「建築物實施耐震能力評估及補強方案」核定本,台灣地區之震區劃分比較,了解對四大都會區會有影響的地震,其震央地點與規模深度。四大都會區中是什麼測站,比較容易超過建築物耐震能力規範,從四大都會區找到最容易發生比較大水平加速度值測站,了解影響這些測站所有地震震央及產生地點的分佈。 根據分析得知,台北盆地地震在震波傳遞上,東南方向的地震其震波比較容易在台北盆地產生聚焦效應。超過建築物耐震規範,在12年總共有7個地震,所以台北盆地劃分在地震乙區是不夠。TAP022(信義國小),這個地方是台北盆地水平加速度值比較大地區。 而台中縣市,而且震央大部份在南投地區及靠台中地區比較近地方,由其是東南方向地震最多,是影響到這地區最多震央來源。台中縣市超過建築物耐震規範,在12年中總共發生6次,都發生在1999年9月20日,主要都是921大地震及其餘震,這6次地震震央都發生在車籠埔斷層及大茅埔-雙冬斷層附近或是斷層東邊靠近中央山脈地方。霧峰國小 (TCU 065)與和平鄉德基 (TCU088),是台中縣市水平加速度值比較大地區。 台南縣市是一個受地震震波影響最大區域,也是極度危險地方,發生次數頻率是四個區域最多地方,而影響台南縣市地震震央主要是靠近台南縣市地區的地震,而其東北方嘉義地區影響很大。台南縣市超過台建築物耐震規範,在12年中總共發生5次,這5個震央是大部份發生在木屐寮斷層與六甲斷層附近。楠西國小 (CHY019),後壁國小(CHY049)與善化國小 (CHY099),是台中縣市水平加速度值比較大地區。 高雄縣市影響最多地震震央,發生在其東北方向,集中在六龜斷層,潮州斷層及旗山斷層東邊。高雄縣市沒有測站水平加速度值超過建築物耐震規範,桃源國小 (KAU050)是高雄縣市水平加速度值比較大地區。
Abstract Located on Circum- Pacific seismic belt, Taiwan experiences frequent earthquakes. Earthquakes occurring in the western Taiwan may cause much more damage due to mass population in this region, while frequency of earthquake occurrence and their average intensity are higher in the eastern Taiwan. The purpose of this paper is to use the data collected by the Central Weather Bureau from 1994 ~ 2005 to study the influences of earthquakes, with seismic intensity greater than 4, to four metropolitan areas (Taipei basin, Taichung area, Tainan area and Kaohsiung area) in the western Taiwan. The seismic intensity is obtained from the maximum value of PGA’s (Peak Ground Acceleration) in the south-north, east-west and vertical directions. According to the seismic zonation in Taiwan area of “Solution for buildings implementing seismic evaluation and reinforcement” cases with high horizontal accelerations at all stations in four metro areas will be extracted to study their distributions and influences in four metropolitan areas. The seismic waves generated by the earthquakes occurring in the southeastern direction of Taiwan basin tend to focus. Seven earthquakes in twelve years exceeded current seismic codes. This shows a reinforcement for the current seismic codes for Taipei basin is needed. Station TAP022 experienced higher horizontal accelerations in Taipei basin. Earthquakes influencing Taichung area mostly occurred in Nantou area and the outskirt of Taichung area, especially from the southeast. Six earthquakes in twelve years exceeded the current seismic codes, and all belonged to the Chi-Chi earthquake and its aftershocks occurred in the vicinity of the Chelungpu Fault and Tamaopu-Shuangtung Fault on September 20, 1999. Station TCU065 and TCU088 experienced higher horizontal accelerations in Taichung area. The frequency of earthquake occurrence in Tainan area is highest among four metro areas. Earthquakes influencing Tainan area mostly occurred in the outskirt of Tainan area, especially from Chiayi area in the northeast of Tainan area. Five earthquakes in twelve years exceeded the current seismic codes, and all five occurred in the vicinity of Muchiliao Fault and Liuchia Fault. Stations CHY019, CHY049 and CHY099 experienced higher horizontal accelerations in Tainan metro area. Most earthquakes striking Kaohsiung area originated from the northeast of Kaohsiung area, mainly from the Liouguei Fault, Chaochou Fault, and the eastern side of Chishan Fault. All horizontal accelerations recorded by stations in Kaohsiung area are below the current seismic codes. Station KAU050 experienced higher horizontal accelerations in Kaohsiung metro area.
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地震, Earthquakes
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