Coseismic Coulomb stress changes induced by a 2020-2021 M_(W)>7.0 Alaska earthquake sequence in and around the Shumagin gap and its influence on the Alaska-Aleutian subduction interface  

作　　者：Lei Yang Jianjun Wang Caijun Xu 

机构地区：[1]School of Geodesy and Geomatics,Wuhan University,Wuhan 430079,China [2]Collaborative Innovation Center of Geospatial Technology,Wuhan 430079,China [3]Key Laboratory of Geospace Environment and Geodesy,Ministry of Education,Wuhan University,Wuhan 430079,China

出　　处：《Geodesy and Geodynamics》2024年第1期1-12,共12页大地测量与地球动力学（英文版）

基　　金：supported by grants from the National Natural Science Foundation of China(Grant No.sU2139205,41774011,41874011);the National Key Research and Development Program of China(Grant No.2018YFC1503605)。

摘　　要：Three M_(W)>7.0 earthquakes in 2020-2021 occurred in the Shumagin seismic gap and its adjacent area of the Alaska-Aleutian subduction zone,including the Mw7.8 Simeonof thrust earthquake on July 22,2020,the M_(W)7.6 Sand Point strike-slip earthquake on October 19,2020,and the M_(W)8.2 Chignik thrust earthquake on July 29,2021.The spatial and temporal proximity of these three earthquakes prompts us to probe stress-triggering effects among them.Here we examine the coseismic Coulomb stress change imparted by the three earthquakes and their influence on the subduction interface.Our results show that:(1)The Simeonof earthquake has strong loading effects on the subsequent Sand Point and Chignik earthquakes,with the Coulomb stress changes of 3.95 bars and 2.89 bars,respectively.The Coulomb stress change caused by the Sand Point earthquake at the hypocenter of the Chignik earthquake is merely around 0.01 bars,suggesting the negligible triggering effect on the latter earthquake;(2)The triggering effects of the Simeonof,Sand Point,and Chignik earthquakes on aftershocks within three months are not well pronounced because of the triggering rates of 38%,14%,and 43%respectively.Other factors may have played an important role in promoting the occurrence of these aftershocks,such as the roughness of the subduction interface,the complicated velocity structure of the lithosphere,and the heterogeneous prestress therein;(3)The three earthquakes caused remarkable coseismic Coulomb stress changes at the subduction interface nearby these mainshocks,with an average Coulomb stress change of 3.2 bars in the shallow region directly inwards the trench.

关 键 词：The 2020-2021 Alaska earthquake SEQUENCE Coseismic Coulomb stress change Mainshock-aftershock triggering The Alaska-Aleutian subduction interface The Shumagin gap 

分 类 号：P315.2[天文地球—地震学]