| 摘要: | 論文名稱︰利用微地動量測探討台灣地區之場址效應 校所組別︰國立中央大學 地球物理研究所 畢業時間及提要別︰九十七學年度 第二學期 碩士學位論文提要 研究生︰黃雋彥 指導教授︰溫國樑 博士 論文提要內容︰ 本研究的區域是台灣全區，整合前人所做台灣各盆地平原區域的微地動資 料，使用相同的標準及方法試圖做出全區域的場址效應研究。傳統上使用的雙站 頻譜比法具有可同時去除來自震源與路徑效應的優點，然而要選擇一個適當的參 考測站並不容易，因此Nakamura(1989)提出單站頻譜比法作為分析微地動資料的 方法;由於使用單站頻譜比法不需要參考站，在應用上方便了許多，利用計算同 一測點之水平相對於垂直向的頻譜比（H/V ratio）估算場址之主頻及震幅放大 因子，進而推估地表沈積物厚度及可換算為地表震波速度等所需資訊，探討當地 的場址效應。再展示台灣地區主頻分佈圖及不同頻率的各區域放大倍率分佈圖， 並且跟地質及一些已知速度構造分布做比對，映證所得的結果。目前已知在沖積 層較厚的地區其主頻值較低，相對的沖積層較薄(岩盤站)的位置主頻值會較高或 是沒有明顯放大的現象，除了沖積層的厚度外，沖積層剪力波波速也是會影響主 頻大小，相同的沖積層厚度，礫岩堆積會比砂泥堆積主頻來的大。而不同頻率的 放大倍率分佈圖則可以反映一些微小的地層變化存在，例如在高頻區域放大倍率 較高可能代表著測點位置比較靠近山區，沖積層較薄等現象；低頻區域放大倍率 較高則可能反映河流經過或沖積平原、盆地等沖積層較厚的地區。 運用此方法還可以做液化潛能的頻估，傳統一般液化潛能的評估，需檢查基 地土層之標準貫入試驗N 值，若基地土層之N 值落於液化型及疑問型土壤，再進 行更詳細的液化潛能評估，詳細評估耗時及冗雜。本研究利用Nakamura 於1996 年提出利用單站頻譜比法之主頻及放大倍率，可精準地估算地表及建築物地震災 害，計算之Kg值可做為分析場址的液化潛能指數以評估各地液化潛能，並將其結 果與國家地震工程中心部分地區已有成果之液化潛能圖做比對。 最後再將這些結果套疊已知的地質區域圖層來做比較討論，結合GIS地理資 訊系統的軟體展示結果，期望本研究能提供一些地震防災、地震危害分析、建築 物耐震設計、土地使用規劃及土壤液化潛能評估作參考。 關鍵字：場址效應、台灣、單站頻譜比法、微地動、土壤液化 Using Microtremor Measurement To Study The Site Effect In Taiwan Area Jyun-yan Huang Instisute of Geophysics, National Central University, Chungli, Taiwan, R.O.C. ABSTRACT In this study, the high density microtremor surveys are done in whole Taiwan except the mountain area. The studying regions include Taipei basin, Taoyuan, Hsinchu and Miaoli, Taichung basin, Chianan Plain, Kaohsiung, Pintung, Hualien, Taidong and Yilan plain. The main idea of this study is to integrate the different area’s results which finished by predecessors, and use the same standard to process data again, in order to study the site effect in whole Taiwan. The two-station spectral ratio method was used to figure out the local site effect previously. But now, in this study, we use the H/V spectral ratio method (Nakamura, 1989) to do the research. If we used the two-station spectral method, the referent rock site station will be difficult to find, so we choose the H/V spectral ratio method because it can figure out the site effect only by using a single station. The dominant frequency and amplification ratio of each survey point were calculated, and reduced it into site conditions, such as thickness of the deposition and the S-wave velocity. The equivalent contours of the dominant frequency and the H/V ratio in different frequency bands were plotted. The dominant frequency shows that the station with thin deposition like rock site, show the higher dominant frequency. On the other hand, the station with thick deposition, it goes low. The dominant frequency also response the S-wave velocity, in which station the S-wave velocity become lower, the dominant frequency become lower too. Traditionally, estimating the potential of liquefaction takes time and the processes are multifarious. Nakamura(1996) found the relationship between potential of liquefaction and the factors in the H/V spectral method, includes dominant frequency and amplitude ratio. That we can calculate the potential of liquefaction quickly now and compared the results with NCREE’s results in this study. Final, the results are combined with the GIS system to spread out. And hope these results can be used in many purposes like earthquake engineering, disaster prevention and cure, seismic analysis and design of structure. （Key words：site effect、microtremor、spectral ratio、Taiwan） |
