Rupture-dependent breakdown energy in fault models with thermo-hydro-mechanical processes
Rupture-dependent breakdown energy in fault models with thermo-hydro-mechanical processes
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DOI：
10.5194/se-11-2283-2020
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发表时间：
2020-11-26
期刊：
影响因子：
3.4
通讯作者：
Lapusta, Nadia
中科院分区：
文献类型：
--
作者：
Lambert, Valere;Lapusta, Nadia
对震源过程的深入了解是由于考虑了类似于断裂力学中黏聚带剪切裂缝的摩擦破裂。这种类比适用于断层摩擦的滑移弱化表征，它以击穿能的形式封装了对破裂传播的阻力，类似于断裂能，这是预先规定的，就好像它是断层界面的材料属性一样。在这里，我们使用由于孔隙流体的热加压而增强减弱的地震序列的数值模型来显示在动态剪切破裂过程中如何计算热-水-力学过程使破裂能量依赖于破裂。我们发现，局部击穿能量既不是一个恒定的材料特性，也不是由破裂过程中获得的滑移量唯一定义的，而是取决于在破裂过程中如何通过滑移率和动应力变化的历史来实现滑移。因此，沿断层同一位置的摩擦击穿能量在经过的不同地震破裂中能有显著差异。这些结果表明，需要重新审视动态破裂模型中常见的预定摩擦击穿能假设，并更好地理解在热-水-机械过程存在的情况下控制破裂动力学的因素。
Substantial insight into earthquake source processes has resulted from considering frictional ruptures analogous to cohesive-zone shear cracks from fracture mechanics. This analogy holds for slip-weakening representations of fault friction that encapsulate the resistance to rupture propagation in the form of breakdown energy, analogous to fracture energy, prescribed in advance as if it were a material property of the fault interface. Here, we use numerical models of earthquake sequences with enhanced weakening due to thermal pressurization of pore fluids to show how accounting for thermo-hydro-mechanical processes during dynamic shear ruptures makes breakdown energy rupture-dependent. We find that local breakdown energy is neither a constant material property nor uniquely defined by the amount of slip attained during rupture, but depends on how that slip is achieved through the history of slip rate and dynamic stress changes during the rupture process. As a consequence, the frictional breakdown energy of the same location along the fault can vary significantly in different earthquake ruptures that pass through. These results suggest the need to reexamine the assumption of predetermined frictional breakdown energy common in dynamic rupture modeling and to better understand the factors that control rupture dynamics in the presence of thermo-hydro-mechanical processes.