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DOI	10.1016/j.epsl.2021.116879
	The 22 July 2020 MW 7.8 Shumagin seismic gap earthquake: Partial rupture of a weakly coupled megathrust
	Ye L.; Lay T.; Kanamori H.; Yamazaki Y.; Cheung K.F.
发表日期	2021
ISSN	0012821X
卷号	562
英文摘要	The earthquake potential of the Shumagin seismic gap along the Alaska Peninsula (∼162°W to ∼158.5°W) has been debated for more than 40 years. On 22 July 2020, the eastern half of the gap hosted an MW 7.8 earthquake involving a patchy rupture of the megathrust in the depth range of 20 to 45 km. The space-time slip distribution is determined by joint inversion of teleseismic P and SH waves and static displacements from regional GPS stations. The event initiated near the epicenter of the 10 November 1938 (MW 8.2) event, and ruptured westward, with little/no overlap with the 1938 rupture zone. The main slip patch has peak slip of ∼3.8 m below the Shumagin Islands, and produced ∼30 cm uplift and ∼25 cm SSE horizontal displacement on Chernabura Island. The slip model predicts well the small (<1 cm) tsunami signals persisting for more than ten hours observed at deep-water DART seafloor pressure recordings along the Alaska-Aleutian arc. Aftershocks with depths from 20 to 40 km fringe the large-slip patches, and show westward concentration during the first month after the mainshock. Aftershocks up-dip of the 1948 MW 7.1 event contribute to the high level of modest-size background seismicity extending to the trench in the region of very low seismic coupling (0.0–0.1) in the western Shumagin gap east of the 1 April 1946 (MW 8.6) rupture zone. The 31 May 1917 event is the last major earthquake to rupture the eastern half of the Shumagin gap, and has a lower surface wave magnitude (MSG-R 7.4, horizontal components) compared to the 2020 event (MSG-R 7.7, vertical components). Comparison of instrument-equalized waveforms for the 1917 and 2020 events indicates similar size contrast and differences in overall rupture duration and slip complexity. The 2020 rupture has average slip of ∼1.9 m over the 3600 km2 region with co-seismic slip ≥1 m. This is much less than the ∼6.7 m of potentially accumulated slip deficit since 1917, consistent with geodetic estimates of low average seismic coupling coefficient of 0.1–0.4. The megathrust seaward of the 2020 event has low seismicity and may either be aseismic or capable of comparable size ruptures. Comparisons are made with other subduction zones that have experienced relatively deep megathrust slip in regions with moderate seismic coupling. © 2021 Elsevier B.V.
关键词	Alaska Peninsula earthquakes finite-fault inversion megathrust coupling seismic gaps Shumagin gap
英文关键词	Earthquake effects; Surface waves; Alaska peninsula earthquake; Finite fault inversions; Megathrust; Megathrust coupling; Partial rupture; Rupture zone; Seismic coupling; Seismic gaps; Shumagin; Shumagin gap; Shear waves; earthquake event; earthquake magnitude; earthquake rupture; fault zone; finite element method; seismic zone; seismicity; Alaska; Alaska Peninsula; United States
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/203355
作者单位	Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen, 518055, China; Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou, China; Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, United States; Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125, United States; Department of Ocean and Resources Engineering, University of Hawaii at Manoa, Honolulu, HI 96822, United States
推荐引用方式 GB/T 7714	Ye L.,Lay T.,Kanamori H.,et al. The 22 July 2020 MW 7.8 Shumagin seismic gap earthquake: Partial rupture of a weakly coupled megathrust[J],2021,562.
APA	Ye L.,Lay T.,Kanamori H.,Yamazaki Y.,&Cheung K.F..(2021).The 22 July 2020 MW 7.8 Shumagin seismic gap earthquake: Partial rupture of a weakly coupled megathrust.Earth and Planetary Science Letters,562.
MLA	Ye L.,et al."The 22 July 2020 MW 7.8 Shumagin seismic gap earthquake: Partial rupture of a weakly coupled megathrust".Earth and Planetary Science Letters 562(2021).