Shear strength of a shear zone in the brittle-plastic transition based on tensorial strain partitioning
Shear strength of a shear zone in the brittle-plastic transition based on tensorial strain partitioning
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DOI：
10.1016/j.jsg.2021.104313
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发表时间：
2021-05
影响因子：
3.1
通讯作者：
H. Noda
中科院分区：
文献类型：
--
作者：
H. Noda
脆性-塑性转变中剪切带的本构规律对于认识大地震前发震层底部的荷载具有重要意义。以往基于微物理的模型是基于将剪切带法向的滑移和扩张划分为不同的变形机制。在这里，我考虑了剩余的二维应变分量，剪切区的非弹性扩展，以及平行于剪切区的相关应力积累，并研究了斜面滑移和大块塑性流动共存的剪切区的稳态行为。数值求解了两种机构的运动约束和本构规律。结果表明：相对于摩擦规律，滑移面的倾斜导致了滑移面的减弱。对于BPT中速率减弱滑动单元，先前的双机制模型得出的强度大于摩擦定律，而本模型定性地解决了这一问题。当滑移面的摩擦系数在Byerlee定律范围内时，断层平行压缩累积可以在BPT和脆性状态下超过法向应力。这项研究阐明了断层平行压缩在理解剪切带的构造和强度方面的重要性。
A constitutive law of shear zones in the brittle-plastic transition (BPT) is of great importance to understanding loading at the bottom of the seismogenic layer preceding large earthquakes. Previous microphysics-based models are based on the partitioning of slip and dilation normal to the shear zone into different deformation mechanisms. Here, I account for the remaining 2-D strain component, inelastic extension of the shear zone, and associated stress buildup parallel to the shear zone, and investigate the steady-state behavior of a shear zone in which slip on inclined planes and bulk plastic flow coexist. Kinematic constraints and constitutive laws of the two mechanisms were solved numerically. The results show that the inclination of slip planes causes weakening relative to the friction law. Whereas the previous two-mechanism model yields a larger strength than the friction law for a rate-weakening slip element in the BPT, the present model qualitatively resolves this problem. Fault-parallel compression buildup can exceed the normal stress in the BPT and the brittle regime if the friction coefficient of the slip planes is in the range of Byerlee's law. This study illuminates the importance of fault-parallel compression in understanding the fabrics and strengths of shear zones.