台灣地區大型地震產生的庫倫應力變化與地震活動相關性

The association of the seismicity and the Coulomb stress change after large earthquakes in Taiwan region

吳宗翰(Tsung-Han Wu)

指導教授 ： 馬國鳳

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

大型地震所釋放的應力可能藉由轉移與累積來觸發鄰近區域的地震，從觀察應力變化可以推測地震的活動變化。台灣地區頻繁的地震活動，地震資料也相當豐富，藉由討論大型地震產生的庫倫應力變化與地震活動相關性，將可以對台灣的地震特性有更多的認識。
本研究選取三個在台灣具有代表性的大型地震，分別是1999年9月21日的集集地震、2002年3月31日的花蓮外海地震、2003年12月10日的台東成功地震，計算這三個地震所造成的庫倫應力變化並觀察與所在區域長時間地震活動的相關性。我們發現若將各區域裡地震的震源機制列入考慮，不同的機制分別統計後發現，明顯有多數地震位於應力變化為正值的區域。同時研究測試大地應力選取的不同以及強震的應力變化累積對之後地震的影響，發現若選擇適當的大地應力，位於應力變化正向區域的地震將明顯增加；應力變化的累積對於地震活動的變化也有一定的影響。
最後利用統計方法來進行一些應力變化以及地震的討論。以921地震進行探討，整體而言，後續地震規模大小與應力變化大小之間有一定程度的相關性；另外地震有集中於應力變化正向的特性，且多集中於0到1bar的區間。

關鍵字

庫倫應力變化 ； 地震活動

並列摘要

We exam the association of the seismicity and the Coulomb stress changes after several large earthquakes in Taiwan region. Our study shows that most of large aftershocks occurred in the region with positive Coulomb stress changes, while the seismicity was decreased in the region of negative Coulomb stress changes. By observing the Coulomb stress changes, we might be able to have a further understanding on the occurrence of earthquakes. We choose three large earthquakes in Taiwan to explore the relationship between the Coulomb stress changes and aftershocks. Three large earthquakes were selected, as the Sep.21st , 1999, Chi-Chi earthquake, March 31st , 2002 , Hualien offshore earthquake, and Dec.10th, 2003, Chen-kung earthquake to calculate their Coulomb stress changes. If we consider about the focal mechanism of the aftershocks, lots of the earthquakes will locate at the positive area of the Coulomb stress change. We also test the different stress field, and we find that the suitable stress field keep the more events in positive area. And we try the test for accumulation of stress change, the number of events in positive area have be changed. We made a statistical studies to evaluate the occurrence of the aftershocks to the corresponding Coulomb stress change. Our result was made to the relation of earthquake magnitude, distribution and the Coulomb stress change. We found that earthquakes are concentrate in the area of having Coulombs stress changes of 0 to 1 bars, especially considering the focal mechanism.

並列關鍵字

seismicity ； Coulomb stress change

參考文獻

Wang, J.-H., Chen, K.-C., Lee, T.-Q. (1994). Depth distribution of shallow earthquakes in Taiwan, J. Geol. Soc. China, 37, 125-142

Hardebeck, J. L., L., J. J. Nazareth, and E. Hauksson,1998. The staticstress change triggering model: Constraints from two southern California aftershocks sequences, Journal of Geophysical research,VOL 103, 24427-24437.

Ji, C., D. V. Helmerger, D. J. Wald, and K. –F. Ma,2003. Slip history and dynamic implications of the 1999 Chi-Chi, Taiwan, earthquake, J. Geophys.

Res., 108(B9),2412, doi:10.1029/2002JB001764.

King, G., C. P. King, Stein R., S., and Lin J.,1994. Static Stress Changes and the Triggering of earthquakes, Bulletin of the Seismological Society of America, Vol 84, NO. 3, pp. 935-953.