Internal structure and permeability of the Nojima fault, southwest Japan
Internal structure and permeability of the Nojima fault, southwest Japan
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DOI：
10.1016/j.jsg.2007.12.002
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发表时间：
2008-04
影响因子：
3.1
通讯作者：
K. Mizoguchi;T. Hirose;T. Shimamoto;E. Fukuyama
中科院分区：
文献类型：
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作者：
K. Mizoguchi;T. Hirose;T. Shimamoto;E. Fukuyama
我们对1995年神户地震期间激活的野岛断裂带中具有代表性的断层岩和周围围岩在各向同性围压高达180MPa的条件下进行了渗透率测量。结果表明：野岛断裂带由低渗透断层泥带（10−20 ~ 10−19m2at 180MPa）和高渗透断层角砾岩破碎带（10−18 ~ 10−14m2at 180MPa）组成。断层泥带是流体流经断层的屏障，而周围的破坏带则是流体管道。这种提出的渗透率结构的性质与从野岛断层0.6和1.8km深度采集的岩心样品进行的测试结果一致。因此，我们提出，从地表暴露的断层岩石中测量断层的渗透率可以作为断层深度达2km的代表性值。根据获得的渗透率数据，我们还研究了神户地震期间野岛断层发生热加压的可能性。我们发现，神户地震期间的摩擦加热会导致4km以下深度的孔隙压力增加，从而导致断层上的摩擦阻力明显减少。
We conducted permeability measurements on representative fault rocks and surrounding country rocks taken from the Nojima fault zone, which was activated during the 1995 Kobe earthquake, under isotropic confining pressures up to 180MPa. The results show that the Nojima fault zone consists of a low-permeability fault gouge zone (10−20–10−19m2at 180MPa) within a high-permeability damaged zone of fault breccia and fractured host rock (10−18–10−14m2at 180MPa). The fault gouge zone acts as a barrier to fluid flow across the fault, whereas the surrounding damage zone acts as a fluid conduit. The nature of this proposed permeability structure is consistent with the results of tests conducted on drillcore samples collected from the Nojima fault at depths of 0.6 and 1.8km. We therefore propose that the permeability of a fault measured from fault rocks exposed at the surface can be used as a representative value for the fault to depths of up to 2km. We also examined the possibility that thermal pressurization occurred upon the Nojima fault during the Kobe earthquake, based on the obtained permeability data. We found that frictional heating during the Kobe earthquake would have led to an increase in pore pressure at depths below 4km, thereby resulting in a marked reduction in frictional resistance upon the fault.