2020年阿拉斯加MW7.8地震断层滑动反演及其触发影响研究

doi:10.12196/j.issn.1000-3274.2022.02.009

摘要/Abstract

摘要： 2020年7月22日, 在北美板块和太平洋板块交界区的阿拉斯加半岛阿留申俯冲带上发生了M_W7.8逆冲地震, 三个月后距震中西南80 km处发生了M_W7.6走滑地震, 一年后距震中东南50 km处发生了M_W8.2逆冲地震。本文基于GPS同震形变, 利用非负最小二乘方法反演了M_W7.8地震的断层同震破裂滑动分布, 研究其变形特征, 并基于地震位错理论计算了该地震对后续两个地震的库仑应力影响。地震断层滑动反演结果显示地震矩为9.28×10²⁰ N·m, 矩震级为M_W7.8; 断层破裂滑移自震中沿断层向SWW向延伸, 在震中西南侧断层滑动量较大, 深度范围集中在25~45 km, 最大滑动量为2.26 m。同震形变符合海沟特大地震的逆冲断层弹性回跳理论模式。库仑应力变化计算结果显示2020年阿拉斯加M_W7.8地震的库仑应力加载触发了M_W7.6走滑地震, 并加速了2021年M_W8.2逆冲地震的发生。

关键词: 2020年阿拉斯加M_W7.8地震, 同震位移, 断层滑动分布, 库仑应力, 地震触发

Abstract: On July 22, 2020, an M_W7.8 earthquake occurred in the Aleutian subduction zone of Alaska Peninsula at the junction of the North American plate and the Pacific plate. Three months later, the M_W7.6 intraplate strike-slip aftershock occurred 80 km away from the epicenter in the Shumajin Gap. One year later, the M_W8.2 earthquake occurred 50 km southeast of the epicenter. Based on GPS coseismic deformation, the approach of non-negative least squares was applied to inverse the fault rupture slip distribution of the earthquake. The result shows that the seismic moment is at about 9.28×10²⁰ N·m, and the moment magnitude is M_W7.8. The fault rupture slip extends from the epicenter along the fault to the SWW direction, and the magnitude of fault slip is larger in the southwest side of the epicenter. The depth range of the area with a large amount of slip is concentrated in the range of 25~45 km, and the maximum amount of slip is 2.26 m. This co-seismic deformation is consistent with the elastic rebound model of the subduction zone thrust fault. Coulomb stress results show that the 2020 M_W7.8 earthquake in Alaska can trigger the thrust aftershocks, the M_W7.6 strike-slip earthquake, and the 2021 M_W8.2 thrust earthquake.

Key words: the 2020 Alaska M_W7.8 earthquake, Coseismic displacement, Fault slip distribution, Coulomb stress, Earthquake triggering

中图分类号:

P315.7

王玉婷, 王武星, 周新, 刘琦, 朱雨菲. 2020年阿拉斯加M_W7.8地震断层滑动反演及其触发影响研究[J]. 地震, 2022, 42(2): 111-122.

WANG Yu-ting, WANG Wu-xing, ZHOU Xin, LIU Qi, ZHU Yu-Fei. Inversion of Fault Slip from the 2020 Alaska M_W7.8 Earthquake and its Triggering Effects[J]. EARTHQUAKE, 2022, 42(2): 111-122.

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