Three-dimensional body wave velocity structure and seismogenic structure for the 2022 M S 6.8 Luding earthquake sequence in Sichuan, China
Three-dimensional body wave velocity structure and seismogenic structure for the 2022 M S 6.8 Luding earthquake sequence in Sichuan, China
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DOI：
10.3389/feart.2023.1099744
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发表时间：
2023-02
期刊：
影响因子：
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通讯作者：
Guangyao Cai;Weilai Wang;Jianping Wu;Jinrong Su;Guijuan Lai;Peng Wu;Liyi Chen;Jun Su
中科院分区：
文献类型：
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作者：
Guangyao Cai;Weilai Wang;Jianping Wu;Jinrong Su;Guijuan Lai;Peng Wu;Liyi Chen;Jun Su
2022年9月5日，鲜水河断裂带东南段泸定县发生6.8级地震，造成重大人员伤亡和严重财产损失。利用震源周围61个地震台站的数据，利用基于机器学习的LOC-FLOW进行相位提取和关联，共获得13496次余震。我们还整理了主震附近的2331次预震。然后利用双差层析成像技术进行事件定位和三维纵、横波速度结构反演。与手工编目相比，该编目具有更高的准确性和完整性。重新定位结果表明，主震发生在鲜水河断裂带磨溪段，震源深度为9.2 km。在震源深度5 ~ 13 km处存在一条长35 km的东南向地震带，主震西侧和西北侧存在两个较浅的地震群。此外，在主震的西北方向存在明显的地震间隙。根据余震序列的空间格局，推测鲜水河断裂带磨溪段为发震断裂带。地震主要位于低速和低泊松比区域，这与鲜水河断裂东南段花岗岩的地质分布一致。主震西北部和东南部存在两个高速带，推测这两个高速带控制了泸定6.8级地震的破裂规模。
An M S 6.8 earthquake struck the Luding county in the southeastern section of the Xianshuihe fault on 5 September 2022, causing heavy casualties and serious property losses. Using the data of 61 seismic stations surrounding the focal area, we utilize the machine learning-based LOC-FLOW for phase picking and association, and obtain a total of 13,496 aftershocks. We also collate 2,331 preshocks near the mainshock. We then conduct event relocation and three-dimensional P- and S-wave velocity structure inversion by double-difference tomography. The catalog we obtained has higher accuracy and completeness than the manual catalog. The relocation results show that the mainshock struck the Moxi section of the Xianshuihe fault at 9.2 km depth. There is a southeast-striking seismic strip of 35 km long at 5–13 km depth, and two relatively shallow seismic clusters exist to the west and northwest of the mainshock. Furthermore, there is an obvious seismic gap to the northwest of the mainshock. Based on the spatial pattern of the aftershock sequence, we speculate that the Moxi section of the Xianshuihe fault is the seismogenic fault. The earthquakes are mainly located in the regions of low velocity and low Poisson’s ratio, which is consistent with the granite that is geologically distributed along the southeast section of the Xianshuihe fault. There are two high-velocity zones located to the northwest and southeast of the mainshock, which are speculated to have controlled the rupture scale of the M S 6.8 Luding earthquake.