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|高屏地區場址效應之探討;Study of site effect in the Kaoping area, Southwestern Taiwan
|高屏地區;場址分類;場址效應;單站頻譜比法;Kaoping area;site classification;site effect
|2009-09-22 09:53:22 (UTC+8)
|本研究採用中央氣象局台灣強地動觀測計畫（Taiwan Strong Motion Instrumentation Program；TSMIP）中，KAU測站在1993∼1998年間所收錄的地震記錄，並使用單站頻譜比法來研究高屏地區的場址效應，並由其加速度反應譜之H/V頻譜比值所得之曲線分布來進行場址分類。本研究的目的，是希望其場址分類可提供 Haz-Taiwan 地震災害評估軟體來應用，而其針對場址效應所作之分析，可提供工程建築耐震設計之參考，以降低地震所帶來的災害與損失。 本研究所得出之B、C、D、E類型的頻率範圍與曲線模式，為：（1）B類型反應譜比曲線在0.5∼2Hz 時，比值較小，在2Hz 之後，比值逐漸變大，且在5Hz左右有明顯的峰值出現。（2）C類型反應譜比曲線和B類型相似，只是峰值往低頻移動，大約在3Hz左右。（3）D類型反應譜比曲線峰值出現在2∼3Hz之間，且其比值明顯大於B、C類型的值。（4）E類型反應譜比曲線峰值出現在1.3Hz附近，其比值略小於D類型的值，且峰值的頻帶範圍較D類型來得寬。 由不同頻率的傅氏振幅譜H/V等值圖之分布形態，可得下列結論：（a）大寮到屏東之間：在0.3∼1Hz有明顯的放大效應。（b）屏東平原出海口附近：在0.1∼2Hz有明顯的場址放大效應，2Hz以上逐漸往內陸移動。（c）屏東平原的沖積層厚度由東北往西南邊增厚。（d）高雄市的前鎮、小港附近：在0.5∼1.5Hz有明顯的場址放大。 The strong motion records observed by KAU stations during the period from 1993 to 1998, which were collected by the Taiwan Strong Motion Instrumentation Program (TSMIP) of CWB, are adopted in this research. The single station spectral ratio method was used in this study to analyze the site effect in the area of southwestern Taiwan. Therefore, we can do the site classification from the H/V spectral ratio of response spectrum. The objective of this research is to provide the information of site category for the seismic loss estimation program, Haz-Taiwan. Furthermore, the analyses of site effects can be taken as reference for the seismic resistance designs and do favors to reducing damages and disasters resulted from earthquakes. In this research, we obtained the frequency ranges and curve models of the B, C, D, and E types, and describe them as the following: (1) The Type B curve of H/V response spectral ratio has a smaller value between 0.5 and 2Hz, but gets larger values after 2Hz. Moreover, it has a peak around 5Hz. (2) The Type C curve is similar to that of Type B, but has its peak at around 3Hz. (3) The peak of Type D curve only exhibits between 2 and 3Hz, and its ratio is obviously bigger than those of Types B and C. (4) Type E curve has its peak at around 1.3Hz, and the ratio is smaller than that of Type D. Moreover, it has a wider frequency bandwidth than Type D around the peak. From the contour of the H/V Fourier spectrum ratio at different frequencies, we got the following conclusions: (a) Between Taliao and Pingtung: it has obvious site amplification exists from 0.3 to 1Hz. (b) Near the seacoast of Pingtung Champaign, obvious magnification of the site effect exists from 0.1 to 2 Hz, and that above 2Hz the contour high area gradually move toward the inland. (c) The thickness of accretion in Pingtung Champaign is getting deeper from the direction of northeast toward southwest. (d) Close to Chienjen and Hsiaokang in Kaohsiung City, there has obvious site amplification effect exists from 0.5 to 1.5Hz.
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