本研究利用以往在台灣苗栗至台中地區中油鑽井及國科會車籠埔斷層科學鑽探的井下電測資料，計算在集集地震前後大地應力場的變化。計算現地應力所需參數包括：孔隙液壓、地殼上覆荷重壓力、以及最大及最小水平應力大小及方向。針對以上參數我們蒐集井下地層測驗、地層密度電測、滲漏及擠壓水泥試驗資料分別求得區域地層垂直應力、地層壓力及最小水平應力隨深度的分佈。最大水平應力可依據下列四種方法求得包括：1)水力破壞試驗 (長時間滲漏試驗或是迷你液裂)；2)井壁剪裂破壞導致的裸孔伸張(borehole breakouts)；3) 鑽井導致人為的伸張裂縫；4) 臨界應力斷層的摩擦理論。以上方法進一步配合高解析度井壁的影像電測、雙偶極剪力波異向性井測或傳統井徑電測，求得井壁附近最大或最小水平應力的方向。利用苗栗-台中地區在集集地震前後車籠埔斷層上、下盤所鑽探約十數口井的資料，我們可以瞭解大地應力場的在大地震前後在時間及空間上的變化。 This research is targeted to study the change of in-situ stress before and after the Chi-Chi earthquake in the Miaoli-Taichung area of western Taiwan using the drilled and log data of oil and gas wells by Chinese Petroleum Corporation (CPC) and Chelungpu-fault scientific drilled hole (TCDP borehole). Parameters needed to calculate in-situ stress include: pore (or formation) pressure, overburden stress, and the maximum and minimum horizontal stresses, and corresponding data include formation test, density logs, leak-off and hydrofrac tests from boreholes will be collected. The maximum horizontal stress can be derived from the following methods: 1) Hydraulic fracturing tests such as extended leak-off test and/or mini-fracs; 2) borehole breakouts from images logs of borehole wall (formation micro-resistivity images); 3) drilling induced tensile fractures, and 4) frictional limit of critically stressed faults. These data, coupled with the image logs, dipole shear image (DSI) logs or traditional caliper logs, can infer the azimuth of the maximum or minimum horizontal stress. From over 10 wells drilled before and after the Chi-Chi earthquake and located in the hanging-wall and footwall of the Chelungpu fault, a quantitative and precise stress state can be obtained and from which the temporal and spatial change of the stress state before and after a large earthquake can be soundly inferred. 研究期間：9908 ~ 10007
