Stress orientations of Taiwan Chelungpu‐Fault Drilling Project (TCDP) hole‐A as observed from geophysical logs
Stress orientations of Taiwan Chelungpu‐Fault Drilling Project (TCDP) hole‐A as observed from geophysical logs
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DOI：
10.1029/2006gl028050
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发表时间：
2007-01
影响因子：
5.2
通讯作者：
Hung-Yu Wu;K. Ma;M. Zoback;N. Boness;Hisao Itô;J. Hung;S. Hickman
中科院分区：
文献类型：
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作者：
Hung-Yu Wu;K. Ma;M. Zoback;N. Boness;Hisao Itô;J. Hung;S. Hickman
台湾车笼埔断层钻探计划（TCDP）钻了一个2公里深的研究钻孔，以调查在1999年Mw7.6集集地震中破裂的车笼埔断层的结构和力学。TCDP的地球物理测井在500-1900米深度进行，包括偶极声波成像仪（DSI）测井和地层微成像仪（FMI）测井，以识别层面、裂缝和剪切带。根据钻孔所取得的连续岩心，在1110公尺深处的一个剪切带被解释为车笼埔断层，它位于金水页岩内，从1013米延伸到1300公尺深处。在几乎整个井筒长度上都观察到应力引起的井眼崩落。这些数据表明，总体应力方向（北纬115 °E）基本上平行于区域应力场，并平行于菲律宾海板块相对于欧亚板块的会聚方向。在不同的深度，平均应力方向的变化。特别是在车笼埔断层附近有一个主要的应力方向异常。在1000米和1310米深处的突然应力旋转接近清水页岩的上边界和下边界，这表明在集集地震期间可能发生了层面滑动。
The Taiwan Chelungpu‐fault Drilling Project (TCDP) drilled a 2‐km‐deep research borehole to investigate the structure and mechanics of the Chelungpu Fault that ruptured in the 1999 Mw 7.6 Chi‐Chi earthquake. Geophysical logs of the TCDP were carried out over depths of 500–1900 m, including Dipole Sonic Imager (DSI) logs and Formation Micro Imager (FMI) logs in order to identify bedding planes, fractures and shear zones. From the continuous core obtained from the borehole, a shear zone at a depth of 1110 meters is interpreted to be the Chelungpu fault, located within the Chinshui Shale, which extends from 1013 to 1300 meters depth. Stress‐induced borehole breakouts were observed over nearly the entire length of the wellbore. These data show an overall stress direction (∼N115°E) that is essentially parallel to the regional stress field and parallel to the convergence direction of the Philippine Sea plate with respect to the Eurasian plate. Variability in the average stress direction is seen at various depths. In particular there is a major stress orientation anomaly in the vicinity of the Chelungpu fault. Abrupt stress rotations at depths of 1000 m and 1310 m are close to the Chinshui Shale's upper and lower boundaries, suggesting the possibility that bedding plane slip occurred during the Chi‐Chi earthquake.