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Cohesive zone length of metagabbro at supershear rupture velocity.
Journal of Seismology ( IF 1.6 ) Pub Date : 2016-06-02 , DOI: 10.1007/s10950-016-9588-2
Eiichi Fukuyama 1 , Shiqing Xu 1 , Futoshi Yamashita 1 , Kazuo Mizoguchi 2
Affiliation  

We investigated the shear strain field ahead of a supershear rupture. The strain array data along the sliding fault surfaces were obtained during the large-scale biaxial friction experiments at the National Research Institute for Earth Science and Disaster Resilience. These friction experiments were done using a pair of meter-scale metagabbro rock specimens whose simulated fault area was 1.5 m × 0.1 m. A 2.6-MPa normal stress was applied with loading velocity of 0.1 mm/s. Near-fault strain was measured by 32 two-component semiconductor strain gauges installed at an interval of 50 mm and 10 mm off the fault and recorded at an interval of 1 MHz. Many stick-slip events were observed in the experiments. We chose ten unilateral rupture events that propagated with supershear rupture velocity without preceding foreshocks. Focusing on the rupture front, stress concentration was observed and sharp stress drop occurred immediately inside the ruptured area. The temporal variation of strain array data is converted to the spatial variation of strain assuming a constant rupture velocity. We picked up the peak strain and zero-crossing strain locations to measure the cohesive zone length. By compiling the stick-slip event data, the cohesive zone length is about 50 mm although it scattered among the events. We could not see any systematic variation at the location but some dependence on the rupture velocity. The cohesive zone length decreases as the rupture velocity increases, especially larger than \( \sqrt{2} \) times the shear wave velocity. This feature is consistent with the theoretical prediction.

中文翻译:

超剪切破裂速度下超生物的内聚区长度。

我们研究了超剪切断裂之前的剪切应变场。沿滑动断层表面的应变阵列数据是在国家地球科学与灾难复原力研究所的大规模双轴摩擦实验中获得的。这些摩擦实验是使用一对米级变质岩标本完成的,其模拟断层面积为1.5 m×0.1 m。施加2.6 MPa的法向应力,加载速度为0.1 mm / s。通过安装32个双组件半导体应变仪来测量近断层应变,该应变计以距断层50 mm和距断层10 mm的间隔安装,并以1 MHz的间隔记录。在实验中观察到许多粘滑事件。我们选择了十个单边破裂事件,这些事件以超剪切破裂速度传播而没有前兆。专注于破裂前沿,观察到应力集中,破裂区域内立即发生急剧的应力下降。假定破裂速度恒定,将应变阵列数据的时间变化转换为应变的空间变化。我们拾取了峰值应变和零交叉应变的位置,以测量内聚区的长度。通过编辑粘滑事件数据,尽管粘滞带长度分散在事件之间,但其粘聚区长度约为50 mm。我们在该位置看不到任何系统的变化,但对破裂速度有一定的依赖性。随着破裂速度的增加,粘结区域的长度减小,尤其是大于 假定破裂速度恒定,将应变阵列数据的时间变化转换为应变的空间变化。我们获得了峰值应变和零交叉应变的位置,以测量内聚区的长度。通过编辑粘滑事件数据,尽管粘滞带长度分散在事件之间,但其粘聚区长度约为50 mm。我们在该位置看不到任何系统的变化,但对破裂速度有一定的依赖性。随着破裂速度的增加,粘结区域的长度减小,尤其是大于 假定破裂速度恒定,将应变阵列数据的时间变化转换为应变的空间变化。我们拾取了峰值应变和零交叉应变的位置,以测量内聚区的长度。通过汇总粘滑事件数据,尽管粘滞带长度分散在事件之间,但其粘聚区长度约为50 mm。我们在该位置看不到任何系统的变化,但对破裂速度有一定的依赖性。随着破裂速度的增加,粘结区域的长度减小,尤其是大于 我们在该位置看不到任何系统的变化,但对破裂速度有一定的依赖性。随着破裂速度的增加,粘结区域的长度减小,尤其是大于 我们在该位置看不到任何系统的变化,但对破裂速度有一定的依赖性。随着破裂速度的增加,粘结区域的长度减小,尤其是大于\(\ sqrt {2} \)乘以剪切波速度。该特征与理论预测相符。
更新日期:2016-06-02
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