Outline of the fault zone drilling project by NIED in the vicinity of the 1995 Hyogo‐ken Nanbu earthquake, Japan
Outline of the fault zone drilling project by NIED in the vicinity of the 1995 Hyogo‐ken Nanbu earthquake, Japan
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NIED 在 1995 年日本兵库县南部地震附近断层带钻探项目概要
DOI：
10.1111/j.1440-1738.2001.00318.x
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发表时间：
2001
期刊：
影响因子：
1.5
通讯作者：
R. Ikeda
中科院分区：
文献类型：
--
作者：
R. Ikeda
摘要日本国立地球科学和防灾研究所（NIED）在1995年兵库县南部（科比）地震震中附近钻了3个钻孔，深度分别为1001 m、1313 m和1838 m，以调查活动断层附近和内部的构造和物质特征。利用这些钻孔，对原地应力、热流、岩心材料性质和地壳电阻率进行了综合研究。特别是，野岛-平林钻孔钻至1838 m的深度，直接覆盖野岛断层，并在1140 m、1313 m和1800 m的深度检测到三个可能的断层链。主要结果如下：（1）断层带附近的剪应力很小，最大水平压缩方向垂直于断层的地表轨迹;（2）根据热流研究结果，余震的下限截止深度估计为300°C左右;（3）将岩心划分为五种类型的断层岩，并确定了这些断层岩在断裂带中的不对称分布模式：（4）围岩的特征是渗透率很低，强度很高;（v）电阻率结构可以用延伸到更大深度但具有低电阻率的断层的模型来解释。
Abstract Three boreholes, 1001 m, 1313 m and 1838 m deep, were drilled by the National Research Institute for Earth Science and Disaster Prevention (NIED) in the vicinity of the epicenter of the 1995 Hyogo‐ken Nanbu (Kobe) earthquake to investigate tectonic and material characteristics near and in active faults. Using these boreholes, an integrated study of the in situ stress, heat flow, and material properties of drill cores and crustal resistivity was conducted. In particular, the Nojima–Hirabayashi borehole was drilled to a depth of 1838 m and directly intersected the Nojima Fault, and three possible fault strands were detected at depths of 1140 m, 1313 m and 1800 m. Major results obtained from this study include the following: (i) shear stress around the fault zone is very small, and the orientation of the maximum horizontal compression is perpendicular to the surface trace of faults; (ii) from the results of a heat flow study, the lower cut‐off depth of the aftershocks was estimated to be roughly 300°C; (iii) cores were classified into five types of fault rocks, and an asymmetric distribution pattern of these fault rocks in the fracture zones was identified; (iv) country rock is characterized by a very low permeability and high strength; and (v) resistivity structure can be explained by a model of a fault extending to greater depths but with low resistivity.