利用LURR方法探討臺灣1994年後大地震之前兆現象

近年來，加卸載響應之比值（Loading/Unloading Response Ratio，LURR）已被應用於大陸、日本、加州等地區，作為中、短期大地震的前兆現象。從破壞力學的觀點來看，一個地震的孕育過程基本上是震源區內岩層的損害過程。LURR的概念就是描述地殼損害過程的演化特性，計算地震活動受到加載和卸載間彼此循環的變化量。加載－卸載的循環是依據最佳震源機制解（斷層可能破裂面之型態）受到地潮（Earth tide）引起的應力變化。本研究使用LURR測試臺灣島內自1994年至2010年，ML>6的地震前之損害過程的預兆現象，分別有1998瑞里地震、1999集集地震、1999嘉義地震、2000花蓮地震、2006卑南地震、2009名間地震與2010甲仙地震。LURR之定義為：在加載和卸載循環過程中，個別的加載響應量X+（應力－應變變化量）與卸載響應量X-的比值，表示為Y=X+/X-。在一個穩定的孕震系統中，Ｙ值大約為１；相反地，當系統達到不穩定狀態時，則Ｙ＞１。響應量可以由地震數目、班尼奧夫應變（Benioff strain）、震源區的破裂長度和面積大小與地震能量來取代。本研究藉由LURR探討上述七個地震事件，發現當響應量為地震能量時，能反映大地震之前兆現象。因此，本研究認為LURR能用來檢測地震異常活動區域與地殼災害性的破裂過程。

關鍵字

庫倫破壞應力；加卸載響應之比值

並列摘要

The load-unload response ratio (LURR) has recently shown promising performance for earthquake forecasting in China, Japan and California. From the viewpoint of fracture mechanics, the preparation process of an earthquake is basically the damage process of the hypocentral media. LURR has been proposed as a measure characterizing the evolution of the damage process of the crust and is calculated from the seismicity variations during loading cycles respectively during the unloading cycles. The loading-unloading cycles are performed by the stress changes induced by the Earth tides acting upon some specific fault plane. In this study, the LURR has been used to detect the precursory damaging process before six large earthquakes, 1998 Rueili, 1999 Chi-Chi, 1999 Chiayi, 2000 Hualien, 2006 Peinan, 2009 Mingjian and 2010 Jiashian, Taiwan, earthquakes. LURR is defined as Y=X+/X-, where X+ and X- are the response rates during loading and unloading cycles, respectively. When a seismogenic system is relatively stable Y ~ 1. To the contrary, when the system is in an unstable state Y > 1. The response rates can be determined from either earthquake numbers, the Benioff strain, the size (length or area) scales of the focal zone or the seismic energy. Using the LURR index as presented in this study, the epicenters of these main shocks was found to exhibit anomalous high LURR values before these two events. We therefore suggest that the LURR approach could be helpful in detecting the anomalous seismicity and catastrophic damaging process of the crust.

並列關鍵字

CFS ； LURR

參考文獻

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利用LURR方法探討臺灣1994年後大地震之前兆現象

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