本研究探討1999年集集大地震（Mw＝7.6）後，於車籠埔斷層下盤附近有一明顯平行八卦台地的地震密集帶，該地震帶在集集地震前鮮有地震活動，受到大地應力改變而觸發。根據1991年3月至2005年7月中央氣象局611筆的短週期地震站資料，選取芮氏規模2.8～8的地震進行三維重新定位、初動法求取震源機制343筆並做應力反演等分析。本研究延續了倪偉峰(2003)的研究，並補足因若干時段地震資料的不足所欠缺的完整性。
本研究利用應力反演後所得到的值（）隨時間的變化，將應力變化分成四個時期:（1）集集地震前淺部地殼(< 14 km)主要以東西伸張的正斷層為主，地震事件發生在八卦台地東南側，其伸張方向為101.5°，值為0.37；（2）震後兩個月內下盤地區同時出現正、逆、走滑酸種機制，其中正斷層為東西伸張、逆斷層為近南北壓縮，走滑斷層的伸張/壓縮軸則與前二者一致；而正斷層最小主應力軸為79°的伸張，值為0.64，逆斷層最大主應力軸為46.1°的擠壓，值為0.48。（3）震後的兩個月後至2001/02則以東西伸張的正斷層為主，並延續至今。其正斷層最小主應力軸呈89°的伸張，值為0.75。（4）2001/02以後，仍以東西伸張的正斷層為主，其最小主應力軸為102°，值為0.93。逆斷層機制完全消失，且出現東西擠壓的走滑斷層機制。由各時期的正斷層應力場均顯示高的值，顯示容易發生主應力軸交換而演變成南北擠壓與東西伸張的走向滑移應力場。整個震後的應力狀態在EW方向上持續減少，NS方向上持續增加；約在震後17個月後（2001/02），EW方向上開始累積應力。深部地殼(> 14km)應力變化可分為三個時期:（1）集集地震前均為近東西方向擠壓的逆斷層，最大主應力軸128.1°，值為0.68；（2）地震後至2000年6月:此時期地震活動幾乎靜止；（3）2000年6月以後:開始出現地震活動，機制仍然為近東西方向擠壓的逆斷層；最大主應力軸為108.4°，值為0.47。深淺地殼所反演的值顯示地震後東西方向水平應力均減少，淺部地殼東西水平應力開始累積的時間點與深部地殼時間點相差約八個月，反映了深淺地殼差異極大的物理性質。

After 1999 Mw 7.6, Chi-Chi, Taiwan earthquake, there is a seismic zone, parallel to the Pakua tableland, in the footwall of Chelungpu fault. The seismic zone was quiet before Chi-Chi earthquake and seemed to be triggered by stress change. In this study, 607 seismic zone data from Central Weather Bureau were being 3D-relocated and double-differenced relocated, 343 earthquake focal mechanisms were determined before analysing stress inversion. We expect to have complete story after filling lacking data in Ni’s (2003) study.
 valuechanges with time is a kind of index to know stress changes relatively (where means the maximum principal axis, means the minimum and is the middle one). We divided four periods of stress change in < 14km depth of footwall area: (1) Before Chi-Chi earthquake, EW-tensioned normal faults are dominant, and seismic zone is focus on the south-eastern side of Pakua tableland. The orintation of is 101.5° with =0.37. (2) In two months after Chi-Chi earthquake, there are normal, thrust and strike-slip faults coexisted in the footwall area. Normal fault mechanisms are in WE tension, thrust mechanism are in close to NS compression, and strike-slip mechanisms have the same P/T axes orientation of normal’s and thrust’s. Stress tensor of normal faults has  value 0.64 with =79°, and direction is 46.1° with  value 0.48. (3) Post two months after Chi-Chi earthquake to Febuary 2001, EW-tensioned normal fault mechanisms are dominant, and the orientation if is 89.0° with  value 0.75. (4) After Febuary 2001, seismicity seems to be quiet compared with prevous period, and thrust fault mechanisms are completely disappear. Deeper crust (> 14km) present three period of stress state: (1) before Chi-Chi earthquake, almost all mechanism are EW thrust faulting, where the direction is 128.1° with  value 0.68; (2) From Chi-Chi E.Q to June 2000, the seismicities are almost quiet; (3) After June 2000, seismic activities began and composed by EW thrust mechanisms, direction is 108.4° with  value 0.47。EW horizontal stress drop was seen on  value, both shallower and deeper crust. The differential time that EW horizontal stress start increasing between shallower and deeper crust is eight months, this reveals extremely different properties of different depth.

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