集集餘震b值與碎形維度分析

Analyses of the b-value and the fractal dimension from the aftershock sequence of the 1999 Chi-Chi, Taiwan, earthquake

王薇茜(Wei-Chien Wang)

指導教授 ： 陳建志

國立中央大學/地球科學學院/地球物理研究所/碩士(2006年)

摘要

集集地震是這半世紀以來，台灣地區規模最大的地震，不僅造成巨大的破壞、近百公里的地表破裂，亦觸發大量餘震，本研究主要利用集集餘震序列進行地震b值及震央震源相關維度D2之分析，並探討兩參數的相關性。選取的地震範圍為集集主震後十二個月內的餘震資料，並將地震資料分成四個時間段，分別為三個月、六個月、九個月以及十二個月。空間上則利用二度分帶座標，東西向由200000至270000公尺，南起2616000公尺，北迄2690000公尺，深度小於30公里的地震，也就是集集震央附近與車籠埔地表破裂的南北界，共涵蓋70×74平方公里。利用空間網格法計算每20×20平方公里網格中兩參數值，在728個網格中，大部份的網格b與D2兩參數都呈現正相關。本研究同時進行了車籠埔地表破裂跡線的碎形維度計算，與地質資料相比，則發現碎形維度與水平位移量趨勢相似，故地表破裂與應變應有密切關係。

關鍵字

b值 ； 集集 ； 碎形維度

並列摘要

Chi-Chi earthquake was the largest earthquake occurred in Taiwan area in this half century, bringing a large number of aftershocks and more than 100 km fault rupture. The aftershock data provides a good opportunity to analyze the relation of b-value and fractal dimension (D2) from a single rupturing process. We chose the earthquakes of 12 months after Chi-Chi main shock, dividing into 4 time spans of 3 months, 6 months, 9 months and 12 months. The selected area with diagonal points of (200000, 2616000) and (270000, 2690000) in the UTM coordinate system and depth less than 30km, could be considered as a whole fracturing system. Therefore, we can find a positive relation between b-value and fractal dimension. We also find the fractal dimension of Chelungpu rupture is correlated to Strike-slip component along the rupture. Based on our result, we propose the fault rupture is closely correlated with strain, and the distribution of aftershocks is related to the status of stress.

並列關鍵字

Chi-Chi ； b-value ； Fractal dimension

參考文獻

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