Effects of prestress state and rupture velocity on dynamic fault branching
Effects of prestress state and rupture velocity on dynamic fault branching
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DOI：
10.1029/2002jb002189
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发表时间：
2003-05-21
影响因子：
3.9
通讯作者：
Dmowska, R
中科院分区：
文献类型：
--
作者：
Kame, N;Rice, JR;Dmowska, R
[1]我们考虑一个模式II破裂传播沿着一个平面的主故障，并遇到一个分支故障的交叉点。使用弹性动力学边界积分方程制定，允许的故障路径是动态的自我选择，我们研究了以下问题：断裂开始沿着的分支？还在继续吗伸展面还是挤压面最有利于分支？主断层上的破裂是否也在继续？破坏用滑移弱化定律来描述，对于该定律，任何滑移量下的强度都与正应力成比例。我们的研究结果表明，破裂尖端周围的动态应力，这增加了破裂速度在主断层面的位置相对于它，可以启动破裂的分支故障。正如先前的工作所建议的，分支破裂是否可以继续到一个更大的规模取决于主应力方向在预应力状态和破裂速度。当我们考虑最大压缩预应力方向与主断层的角度逐渐变浅时，分支破裂最有利的一侧从伸展侧切换到压缩侧。当分支角较宽时，两个断层上的同时破裂可以被激活，但由于断层之间的强烈应力相互作用，对于窄分支角通常是困难的。然而，它也可以被激活的增强动态应力时，破裂速度是非常接近的瑞利速度。自然的例子似乎与我们提出的模拟一致。
[1] We consider a mode II rupture which propagates along a planar main fault and encounters an intersection with a branching fault. Using an elastodynamic boundary integral equation formulation, allowing the failure path to be dynamically self-chosen, we study the following questions: Does the rupture initiate along the branch? Does it continue? Is the extensional or compressional side most favored for branching? Does rupture continue on the main fault too? Failure is described by a slip-weakening law for which the strength at any amount of slip is proportional to normal stress. Our results show that dynamic stresses around the rupture tip, which increase with rupture velocity at locations off the main fault plane relative to those on it, could initiate rupture on a branching fault. As suggested by prior work, whether branched rupture can be continued to a larger scale depends on principal stress directions in the prestress state and on rupture velocity. The most favored side for branching rupture switches from the extensional to the compressional side as we consider progressively shallower angles of the direction of maximum compressive prestress with the main fault. Simultaneous rupturing on both faults can be activated when the branching angle is wide but is usually difficult for a narrow branching angle due to strong stress interactions between faults. However, it can be also be activated by enhanced dynamic stressing when the rupture velocity is very near the Rayleigh velocity. Natural examples seem consistent with the simulations that we present.