Dynamic Rupture Modeling to Investigate the Role of Fault Geometry in Jumping Rupture Between Parallel‐Trace Thrust Faults
Dynamic Rupture Modeling to Investigate the Role of Fault Geometry in Jumping Rupture Between Parallel‐Trace Thrust Faults
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DOI：
10.1785/0120190003
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发表时间：
2019-12
影响因子：
3
通讯作者：
P. Peshette;J. Lozos;D. Yule;E. L. Evans
中科院分区：
文献类型：
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作者：
P. Peshette;J. Lozos;D. Yule;E. L. Evans
对历史上地表破裂逆冲地震的调查表明，破裂可以从一个断层跳到8公里外的另一个断层。此外，还观察到间隔约50公里的逆冲断层之间的跳跃破裂。相反，以前的逆冲断层模拟研究发现，最大跳跃破裂距离仅为0.2公里。在这里，我们提出了一个动态破裂建模参数的研究，试图调和这些差异，并确定几何和应力条件，促进跳跃破裂。我们使用三维有限元方法模拟具有平行表面痕迹和相反倾角方向的逆冲断层对上的破裂。我们改变应力降和断层强度比，以确定在不同倾角和不同的断层之间的最小距离产生跳跃破裂的条件。我们发现，几何形状起着至关重要的作用，在确定是否破裂将跳转到相邻的逆冲断层。破裂更有可能在断层之间跳跃，以更陡的角度彼此倾斜，并且在浅倾角的情况下，行为逐渐减少到没有破裂跳跃。我们的应力参数的变化强调了这些朝向取向的结果。相互倾斜的断层中的破裂跳跃会因应力条件的变化而变得复杂，但最突出的一致性是中倾角断层的破裂很少跳跃。如果初始应力条件已经接近破坏，则长距离跳跃的可能性增加。我们的模型呼吁注意特定的几何和应力条件下，动态破裂前是最重要的跳跃破裂的潜力。然而，我们的模型也强调了由于滑动引起的近场应力变化的重要性。根据我们的建模，破裂跳跃的可能性在很大程度上取决于断层的倾角和方向。
Investigations of historic surface‐rupturing thrust earthquakes suggest that rupture can jump from one fault to another up to 8 km away. Additionally, there are observations of jumping rupture between thrust faults ∼50 km apart. In contrast, previous modeling studies of thrust faults find a maximum jumping rupture distance of merely 0.2 km. Here, we present a dynamic rupture modeling parameter study that attempts to reconcile these differences and determines geometric and stress conditions that promote jumping rupture. We use the 3D finite‐element method to model rupture on pairs of thrust faults with parallel surface traces and opposite dip orientations. We vary stress drop and fault strength ratio to determine conditions that produce jumping rupture at different dip angles and different minimum distance between faults. We find that geometry plays an essential role in determining whether or not rupture will jump to a neighboring thrust fault. Rupture is more likely to jump between faults dipping toward one another at steeper angles, and the behavior tapers down to no rupture jump in shallow dip cases. Our variations of stress parameters emphasize these toward‐orientation results. Rupture jump in faults dipping away from one another is complicated by variations of stress conditions, but the most prominent consistency is that for mid‐dip angle faults rupture rarely jumps. If initial stress conditions are such that they are already close to failure, the possibility of a long‐distance jump increases. Our models call attention to specific geometric and stress conditions where the dynamic rupture front is the most important to potential for jumping rupture. However, our models also highlight the importance of near‐field stress changes due to slip. According to our modeling, the potential for rupture to jump is strongly dependent on both dip angle and orientation of faults.