Stress Changes on the Garlock Fault during and after the 2019 Ridgecrest Earthquake Sequence
Stress Changes on the Garlock Fault during and after the 2019 Ridgecrest Earthquake Sequence
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DOI：
10.31223/osf.io/v7qph
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发表时间：
2020-01
影响因子：
3
通讯作者：
M. Ramos;J. C. Neo;P. Thakur;Yihe Huang;S. Wei
中科院分区：
文献类型：
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作者：
M. Ramos;J. C. Neo;P. Thakur;Yihe Huang;S. Wei
最近发生在南加州的 2019 年 Ridgecrest 地震序列揭示了一系列复杂的级联前震系列，最终形成了 7.1 级主震，对地震学界产生了冲击。但中央加洛克断层尽管位于该层序的南边，但并未发生同震破坏。相反，加洛克断层经历了震后蠕变并表现出相当大的地震群。主震期间破裂过程的动态细节很大程度上是未知的，导致加洛克断层失效所需的应力大小也是未知的。我们使用运动学滑移反演、库仑应力变化 (ΔCFS) 和动态破裂建模等工具组合，对主震期间和之后 Garlock 断层上的应力如何变化提供了一个综合视图。我们表明，正的 ΔCFS 不能轻易解释在加洛克断层上观察到的余震模式，但与中央加洛克断层部分记录的蠕变一致。我们的动力学模型能够重现主震期间的主要滑移粗糙度和运动学估计的破裂速度（≤2 km/s），并表明加洛克断层上法向应力和剪切应力的时间变化在破裂结束时最大。我们从模型中观察到的加洛克断层上最大的静态和动态应力变化与蠕变区域一致，这表明正应力扰动可能是在主震破裂期间或之后造成的。对近场应力变化演化的分析可以深入了解里奇克莱斯特序列如何影响加利福尼亚东部剪切带最北端的局部应力场。
The recent 2019 Ridgecrest earthquake sequence in southern California jostled the seismological community by revealing a complex and cascading foreshock series that culminated in a Mw 7.1 mainshock. But the central Garlock fault, despite being located immediately south of this sequence, did not coseismically fail. Instead, the Garlock fault underwent postseismic creep and exhibited a sizeable earthquake swarm. The dynamic details of the rupture process during the mainshock are largely unknown, as is the amount of stress needed to bring the Garlock fault to failure. We present an integrated view of how stresses changed on the Garlock fault during and after the mainshock using a combination of tools including kinematic slip inversion, Coulomb stress change (ΔCFS), and dynamic rupture modeling. We show that positive ΔCFSs cannot easily explain observed aftershock patterns on the Garlock fault but are consistent with where creep was documented on the central Garlock fault section. Our dynamic model is able to reproduce the main slip asperities and kinematically estimated rupture speeds (≤2 km/s) during the mainshock, and suggests the temporal changes in normal and shear stress on the Garlock fault were the greatest near the end of rupture. The largest static and dynamic stress changes on the Garlock fault we observe from our models coincide with the creeping region, suggesting that positive stress perturbations could have caused this during or after the mainshock rupture. This analysis of near-field stress-change evolution gives insight into how the Ridgecrest sequence influenced the local stress field of the northernmost eastern California shear zone.