InSAR观测揭示的2024年新疆乌什Mw 7.0地震地表形变及发震断层模型

Coseismic Surface Displacements and Source Model of the 2024 Mw 7.0 Wushi (Xinjiang, China) Earthquake Revealed by InSAR Observations

  • 摘要: 2024年1月23日,新疆维吾尔自治区乌什县发生了Mw 7.0地震,本次地震是天山地震带迈丹-沙依拉姆断裂区域近20年以来发生的最大地震,该地震的发生为深入理解天山地震带断层系统的破裂行为和构造活动提供了机会。为确定2024年乌什地震的断层几何和滑动分布并评估区域危险性,利用合成孔径雷达干涉技术研究了2024年乌什地震的发震断层模型。首先利用升、降轨Sentinel-1A卫星雷达影像获取2024年乌什地震的同震地表形变场,然后利用多峰值优化粒子群算法确定本次地震的均匀滑动模型,在此基础上基于非负最小二乘算法反演发震断层的精细滑动分布,最后利用库伦失稳准则评估发震区域周边的地震危险性。研究结果显示,升降轨视线向最大抬升位移~74 cm,最大沉降位移~14 cm;本次地震的发震断层倾向北北西,倾角55°,走向~230°,滑动角~42°,发震断层呈现逆冲兼具左旋走滑分量的运动性质,符合区域活动断裂的运动模式。综合反演结果以及前人的地震地质研究初步判断发震断层为迈丹-沙依拉姆断裂带的次级断裂。库伦应力结果表明,阔克萨勒断裂区域、大石峡断裂区域和托什干断裂(震中西北部分)区域都处于应力加载状态,这些区域未来地震风险需要被重点关注。

     

    Abstract: Objectives: On 23 January 2024, an Mw 7.0 earthquake struck Wushi County (Xinjiang, China). It was the largest earthquake that occurred along the Maidan-Shayilamu fault of the Tianshan Seismic Belt in the last two decades, which provided an opportunity to further examine the rupture behavior and tectonic activity of the fault system in the Tianshan Seismic Belt. Methods: In this study, Interferometric Synthetic Aperture Radar (InSAR) was used to retrieve coseismic surface deformation from Sentinel-1A images. The multipeak particle swarm optimization was employed to invert for fault geometry parameters and subsequently obtained the refined slip distribution based on a bounded-variable least-squares algorithm. Finally, the static Coulomb failure stress change (ΔCFS) was calculated to assess regional seismic hazards. Results: The earthquake led to a maximum line of sight uplift displacement of ~74 cm and a maximum LOS subsidence displacement of ~14 cm. The event had a NNW-dipping fault with a dip of 55°, a strike of ~230°, and a rake of ~42°, indicating that this earthquake was a thrust event with a leftlateral slip component. The slip was concentrated mainly at depths of 8-18 km. The maximum slip was 4.3 m, occurring at a depth of ~10.2 km. The total released moment was 4.25×1019 N·m, equivalent to a moment magnitude Mw 7.05. Conclusions: Our modeling results together with previous geological research suggest that the seismogenic fault is a secondary fault of the MaidanShayilamu fault zone. ΔCFS results indicate high seismic risks in Kuokesale fault region, Dashixia fault region, and the Tuoshigan fault region northwest of the epicenter, which special attention should be paid to.

     

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