Permeability in Fracture Zone nearby the Nojima Fault Estimated Using Strain Changes due to Water Injection Experiments
Permeability in Fracture Zone nearby the Nojima Fault Estimated Using Strain Changes due to Water Injection Experiments
复制标题
利用注水实验引起的应变变化估算野岛断层附近断裂带的渗透率
DOI：
10.4294/zisin1948.56.2_171
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
K. Fujimori
中科院分区：
文献类型：
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作者：
A. Mukai;K. Fujimori
1997年和2000年在1995年日本南部地震破裂带附近1800m深的钻孔进行了注水试验。在这些实验中，用三分量应变仪在800m深的钻孔底部，1800m深的钻孔西南70m处观测到了应变变化的收缩。我们利用应变观测资料估算了野岛断裂附近断裂带的水力性质，以研究地震后断裂的愈合情况。注水引起的应变变化取决于水力参数，如水力扩散率、水力传导性和孔隙流体流动的通道。当我们假设孔隙流体在垂直于野岛断裂的垂直平面上流动时，计算的注水应变变化与观测数据相吻合。断裂带内最小主应力方向与断裂方向平行。认为孔隙流体是通过垂直于断层的裂缝扩散的，因为孔隙压力很容易在最小主应力方向打开裂缝。1997年和2000年的水力扩散系数分别为1.1±0.1m2/S和0.5±0.1m2/S。渗透率的降低表明，断层附近的裂缝在1995年兵库县南部地震后已经愈合。测得渗透系数为1.4~4.3·~10-6m/S，比其他研究估算的一般岩石的渗透系数大约3个数量级。认为渗透率大的原因是：(1)在540m深的浅层地壳中注入了水；(2)在断层附近的断裂带进行了注水试验；(3)裂缝没有完全愈合。
Water injection experiments were performed in 1997 and 2000 at the 1800 m-deep borehole near the fracture zone of the 1995 Hyogoken-Nanbu earthquake. During these experiments, contraction of strain changes was observed with three-component strainmeters at a bottom of 800 m-deep borehole, 70 m southwest of the 1800 m-deep borehole. We estimated hydraulic properties of the fracture zone nearby the Nojima fault using the observational data of strain in order to investigate a healing of the fault at the postseismic stage. Strain changes due to water injection depend on hydraulic parameters, such as hydraulic diffusivity, hydraulic conductivity and channel of pore fluid flow. Calculated strain changes due to water injection agreed with the observational data, when we assumed that pore fluid flowed on a vertical plane perpendicular to the Nojima fault. The orientation of the minimum principal stress is parallel to the fault in the fracture zone. It is considered that pore fluid was diffused through the fractures perpendicular to the fault, because pore pressure could easily open fractures in the orientation of the minimum principal stress. Hydraulic diffusivities in 1997 and 2000 were determined to be 1.1±0.1 and 0.5±0.1 m2/s, respectively. The reduced permeability suggests that the fractures nearby the fault have been healing after the 1995 Hyogo-ken Nanbu earthquake. Hydraulic conductivity was determined to be 1.4-4.3 •~ 10-6 m/s. This value is about three orders of magnitude larger than the hydraulic conductivities of general rocks estimated in other studies. It is considered that the large hydraulic conductivity was attributed to the following facts; (1) water was injected in the shallow crust at the depth of 540 m, (2) the water injection experiments were performed in the fracture zone nearby the fault, (3) a healing of fractures was not completed.
影响因子：
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作者：
BRACE, WF;WALSH, JB;FRANGOS, WT
通讯作者：
FRANGOS, WT