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.

脆塑性转变（BPT）中剪切带的本构定律对于理解大地震之前震源层底部的载荷非常重要。以前基于微物理学的模型是基于将垂直于剪切区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，剪切区域的无弹性延伸以及与剪切区域平行的相关应力累积，并研究了在倾斜平面上滑动和大块塑料的剪切区域的稳态行为流共存。数值求解了这两种机制的运动学约束和本构定律。结果表明，相对于摩擦定律，滑移面的倾斜会导致减弱。尽管对于BPT中速率减弱滑移元素，先前的两种机制模型产生的强度大于摩擦定律，但本模型从质量上解决了该问题。如果滑动面的摩擦系数在拜耳定律的范围内，则断层平行压缩积聚可能会超过BPT和脆性区域中的法向应力。这项研究阐明了断层平行压缩在理解剪切带的结构和强度方面的重要性。