Cohesive zone length of metagabbro at supershear rupture velocity
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- 作者：Eiichi Fukuyama ; Shiqing Xu ; Futoshi Yamashita ; Kazuo Mizoguchi
- 关键词：Dynamic rupture propagation ; Cohesive zone length ; Supershear rupture ; Friction experiments
- 刊名：Journal of Seismology
- 出版年：2016
- 出版时间：October 2016
- 年：2016
- 卷：20
- 期：4
- 页码：1207-1215
- 全文大小：1,079 KB
- 刊物类别：Earth and Environmental Science
- 刊物主题：Earth sciences
Geophysics and Geodesy
Structural Geology
Hydrogeology
Geotechnical Engineering - 出版者：Springer Netherlands
- ISSN：1573-157X
- 卷排序：20
文摘
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.