Evidence of a Supershear Transition Across a Fault Stepover
Evidence of a Supershear Transition Across a Fault Stepover
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DOI：
10.1029/2020gl087400
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发表时间：
2020-05-28
影响因子：
5.2
通讯作者：
Kiser, E. D.
中科院分区：
文献类型：
--
作者：
Kehoe, H. L.;Kiser, E. D.
超剪切地震的传播速度快于地球的剪切波速度，可以在远离破裂断层的地方产生强烈的地面运动。尽管与这些地震相关的危险，但支配它们发生的确切断层属性并没有得到很好的约束。虽然早期的研究将超剪切破裂与简单的断层几何结构联系在一起，但最近的动态破裂模型揭示了复杂断层几何形状(如断层凸起)上的超剪切转变机制。在这里，我们首次观察到在2017年M-W 7.7科曼多尔斯基群岛地震期间断层跨越系统上的超剪切转变。利用高分辨率反投影技术，我们发现地震在两条错动断裂之间的破裂速度从2.1公里/S加速到5.0公里/S，证明了自然界中发生的一种新的超剪切转换机制的可行性。考虑到地球转换板块边界的断层复杂性，这一结果可能会提高我们对超剪切破裂过程及其相关危险的理解。
Supershear earthquakes, propagating faster than the Earth's shear wave velocity, can generate strong ground motion at distances far from the ruptured fault. Despite the hazards associated with these earthquakes, the exact fault properties that govern their occurrence are not well constrained. Although early studies associated supershear ruptures with simple fault geometries, recent dynamic rupture models have revealed a supershear transition mechanism over complex fault geometries such as fault stepovers. Here we present the first observation of a supershear transition on a fault stepover system during the 2017 M-w 7.7 Komandorsky Islands earthquake. Using a high-resolution back-projection technique, we find that the earthquake's rupture velocity accelerates from 2.1 to 5.0 km/s between two offset faults, demonstrating the viability of a new supershear transition mechanism occurring in nature. Given the fault complexity of the Earth's transform plate boundaries, this result may improve our understanding of supershear rupture processes and their associated hazards.