The deep Shumagin gap filled: Kinematic rupture model and slip budget analysis of the 2020 Mw 7.8 Simeonof earthquake constrained by GNSS, global seismic waveforms, and floating InSAR
The deep Shumagin gap filled: Kinematic rupture model and slip budget analysis of the 2020 Mw 7.8 Simeonof earthquake constrained by GNSS, global seismic waveforms, and floating InSAR
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DOI：
10.1016/j.epsl.2021.117241
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发表时间：
2021-10-22
影响因子：
5.3
通讯作者：
Fusso, Logan
中科院分区：
文献类型：
--
作者：
Xiao, Zhuohui;Freymueller, Jeffrey T.;Fusso, Logan
2020年7月22日，西梅翁诺夫7. 8级特大逆冲断层地震袭击阿拉斯加半岛近海。这是自1917年以来在被称为Shumagin地震空区的神秘地区发生的最大事件，Shumagin地震空区是一个过渡板块界面耦合区域，从东部高度耦合到西部蠕动。因此，这一事件提供了一个难得的机会，了解这种不均匀耦合故障的破裂力学。在这项研究中，我们研究了2020年Simeonof地震的破裂过程与静态GNSS位移，干涉合成孔径雷达位移，高速率GNSS波形和地震波形的组合。由于变形场的不连续性，我们使用干涉合成孔径雷达数据的个别岛屿和绑定的位移场，无论是全球导航卫星系统的观测或保持这些“浮动”，即我们在反演过程中估计的模糊度参数。结果表明，这次地震的破裂过程是单向的，从震源向西传播约130 s，平均破裂速度约为1.9km/s。最大滑动集中在小牛寺群岛下方，发生在破裂开始后20 s至50 s之间。我们发现，干涉合成孔径雷达的观测，特别是“浮动”的数据近场岛屿，提供了必要的限制滑动反演，建立信心的滑动耦合区域。与现有和替代板块耦合模型的比较表明，剩余的滑动预算不太可能在30至40公里的深度产生大的事件，因为Shumagin地震空白大部分已被2020年Simeonof地震在这些深度填补。然而，这两个耦合模型表明，在浅近海沟地区的大量的滑动赤字，这表明一个显着的地震仍然可能发生。需要进行海底大地测量观测，以进一步限制海沟附近板块的耦合。(C)2021爱思唯尔有限公司版权所有。
On 22 July 2020, the Mw 7.8 Simeonof megathrust earthquake struck offshore of the Alaska Peninsula. This was the largest event since 1917 in the enigmatic area known as the Shumagin seismic gap, a region of transitional plate interface coupling from highly coupled to the east to creeping to the west. Hence, this event provides a rare chance to understand rupture mechanics on such heterogeneously coupled faults. In this study, we examine the rupture process of the 2020 Simeonof earthquake with a combination of static GNSS displacements, InSAR displacements, high-rate GNSS waveforms and teleseismic waveforms. Due to the discontinuous nature of the deformation field, we use InSAR data for individual islands and tie the displacement field either to GNSS observations or keep these "floating", i.e. we estimate an ambiguity parameter during the inversion. Our results demonstrated that the rupture process of this event is unidirectional, initiating at the hypocenter and propagating westward for about 130 s with an average rupture velocity of similar to 1.9 km/s. The highest slip was centered below the Koniuji Islands and occurred between 20 s to 50 s after the rupture initiation. We find that InSAR observations, especially "floating" data on near-field islands, provide essential constraints for the slip inversion, building confidence in the slipping of the less coupled region. Comparison with an existing and an alternative plate coupling model demonstrated that the remaining slip budget is unlikely to be able to generate a large event at depths from 30 to 40 km, as the Shumagin seismic gap has been mostly filled by the 2020 Simeonof earthquake at those depths. However, both coupling models suggest a substantial slip deficit in shallow near trench regions, suggesting that a significant earthquake can still occur. Seafloor geodetic observations are required to further constrain the near-trench plate coupling. (C) 2021 Elsevier B.V. All rights reserved.