探討不同地質區強震站之淺層S波速度構造; Shallow S-Wave Velocity Structure of Some Strong Motion Stations in Different Geological Areas

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Title:	探討不同地質區強震站之淺層S波速度構造;Shallow S-Wave Velocity Structure of Some Strong Motion Stations in Different Geological Areas
Authors:	郭俊翔;Chun-Hsiang Kuo
Contributors:	地球物理研究所
Keywords:	剪力波;速度構造;微地動陣列;array;microtremor;S-wave;GA;fk;velocity structure
Date:	2004-06-01
Issue Date:	2009-09-22 09:54:43 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	使用微地動陣列法來求取淺部地層的剪力波速度構造在美日等國家已經被廣泛的使用，且證實此一方法在寬闊的沈積平原及盆地有其一定的精確度。本研究特地選定了包括台北盆地、宜蘭平原、花東縱谷等不同地質區的強震站，進行微地動陣列的施測，並比較前人在相同地區的研究以及強震站施測PS-logger和SASW的結果，探討在不同地質區微地動陣列方法所得的剪力波速度構造的準確性。微地動陣列法的原理是假設儀器所接收的平面波皆為水平入射，不同位置的儀器所接收到的相同波相會有一時間差，利用頻率-波數法（簡稱F-K）求得表面波頻散曲線，再利用基因演算法（GA）產生大量高擬合度之速度模型後，進一步使用傳統表面波頻散曲線逆推法加以修正求得精確度更高的剪力波速度構造。本研究最後得到的剪力波速度構造在台北盆地以及蘭陽平原的大部分地區都和前人的研究成果以及鑽井資料相當的吻合，但是在花東縱谷測點的速度構造則和鑽井以及SASW結果有不小的差距，初步認為是由於花東縱谷區的地形起伏和地層水平向速度變化較為劇烈，而造成此現象。TAP022信義國小和TAP089吳興國小位於台北盆地邊緣，原本採用GA方法求出的速度構造也有差異性較大的現象，所以我們嘗試使用淺層折射震測所得到的速度以及厚度來固定GA初始模型的第一二層速度和厚度，經此一步驟之後，信義國小的基盤出現在50公尺深處，而吳興國小的基盤出現在僅5公尺深處，和鑽井的56公尺以及7.6公尺相當接近，此一方法應可作為未來在地表地形以及地下構造變化較劇烈地區施行微地動陣列測量時資料處理方法的改進參考。 We conducted array measurements of microtremors in 17 strong motion stations to estimate shallow S-wave velocity structures. These strong-motion stations are distributed in different geological areas including Taipei Basin, Lan-Yang Plain and Longitudinal Valley. First, we use Frequency-Wavenumber method to estimate phase velocities of microtremors and get the dispersion curve, then use (Genetic Algorithms) GA method to find some good S-wave velocity models, which have high fitness. Finally, we take the GA result as initial model and use the traditional surface wave inversion technique (SURF) to do inversion and estimate the best S-wave velocity model. In the near surface part (depth < 100 meter), we compare our S-wave velocity structures with the models estimated from PS-logger and SASW method. The results of array measurement in most stations of Taipei Basin and Lan-Yang Plain are very similar to results of PS-logger and SASW. It exhibit array measurement of microtremors is suitable for estimating velocity structure on alluvium plain. But these results in Longitudinal Valley are very different due to complex topographic and subsurface structure. We also try to improve our array measurement method to estimate well velocity structure in more complex geological area.
Appears in Collections:	[Graduate Institute of Geophysics] Electronic Thesis & Dissertation

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