High-velocity frictional behavior and microstructure evolution of fault gouge obtained from Nojima fault, southwest Japan
High-velocity frictional behavior and microstructure evolution of fault gouge obtained from Nojima fault, southwest Japan
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DOI：
10.1016/j.tecto.2009.02.033
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发表时间：
2009-06
期刊：
影响因子：
2.9
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
对1995年神户地震期间滑动的野岛断层泥进行了高速实验，研究了与滑动弱化行为相关的物理机制。随着滑移量的增加，在0.62 Mpa法向应力和1.03m/S滑移速度下剪切的断层泥的摩擦值从大于0.6的峰值指数下降到0.2的稳态值。在摩擦弱化阶段，断层泥的结构以颗粒粉碎、斜面和平行剪切面以及具有强烈择优取向的局部变形区为特征，在稳态摩擦阶段以褶皱和飘动结构为特征。基于刮削层附近温度测量的数值模拟表明，在实验期间，量规层内的温度不超过400°C。在滑动-保持-滑动试验中，断层泥在S滑动暂停12次后才观察到完全强度恢复，两次连续滑动的滑动弱化曲线是相同的。当滑移速度从0.006米/S增加到1.03米/S时，稳态摩擦系数从0.8%降至0.2%左右。这种高速弱化特征不仅出现在人造石英泥中，也出现在野岛泥中。尽管目前还不清楚热压、硅胶润滑、闪速加热、排湿等因素中的哪种机制导致了这种弱化，但目前的实验结果表明，这种高速弱化与较高的产热率有关。最后，在变形到最终稳态阶段的样品中观察到的流动结构在以前的慢速实验中从未被报道过，这可能是高速摩擦滑动的关键结构特征。
High-velocity experiments on fault gouge taken from the Nojima fault that slipped during the 1995 Kobe earthquake were conducted to investigate physical mechanism associated with the slip-weakening behavior. With increasing slip, the friction values of the gouge sheared at 0.62 MPa normal stress and 1.03 m/s slip velocity decrease exponentially from a peak value of more than 0.6 to a steady-state value of 0.2. The textures of the gouge are characterized by grain comminution, oblique and parallel shear planes and localized deformation zone with strongly preferred orientation in the friction weakening stage, and folding and fluttering structures at the steady-state friction stage. Numerical modeling based on the temperature measurements close to the gouge layer shows that the temperature inside the gauge layer did not exceed 400 °C during the experiments. In a slide–hold–slide test, a full strength recovery of the fault gouge was observed only after 12 s slip pause and the slip-weakening curves are the same between the two successive slips. The steady-state coefficient of friction decreased from 0.8 to about 0.2 when the slip velocity increased from 0.006 m/s to 1.03 m/s. This high-velocity weakening feature was observed in a synthetic quartz gouge as well as in the Nojima gouge. Although it is unclear which mechanism causes the weakening among thermal pressurization, silica gel lubrication, flash heating, moisture-draining and so on, the present experimental results suggest that the high-velocity weakening is related to the high heat production rate. Finally, the flow structures observed in the samples deformed up to the final steady-state stages have never been reported in previous slow-rate experiments and could be a key structure characteristic of high-velocity frictional sliding.