InSAR观测揭示的2024年西藏尼玛Mw 6.0地震同震破裂行为

Coseismic Rupture Behavior of the 2024 Nima (Tibet) MW 6.0 Earthquake Revealed by InSAR Observations

  • 摘要: 2024年6月1日,青藏高原中北部尼玛县发生了一次MW 6.0浅源地震。作为拉雄错-嘎尔孔茶卡断裂带附近发生的最大地震,此地震的发生为深入理解该研究程度较低区域的发震构造分布及运动特性提供了重要机会。本文利用Sentinel-1A卫星的升、降轨SAR影像获取了该事件的同震地表形变,并探究了其发震构造。尽管InSAR观测反演获取的东北倾和西北倾破裂断层模型均较好地拟合同震形变,但综合分析反演结果、历史地震、区域活动断裂分布及运动特性,推断该地震成核于东北倾(走向325°)倾角83°的右旋走滑断层,可能为拉雄错-嘎尔孔茶卡断裂带的一个隐伏分支断裂。同震滑动最大为0.67 m,主要分布于2.0至12.0 km深度。此外,同震库仑应力变化揭示向阳湖-布若错中分支断裂西段浅部应力可达0.11 bar,具有较高的地震破裂危险。

     

    Abstract: Objectives:On 1 June 2024, a shallow MW 6.0 earthquake struck the Nima County in the North-central Tibetan Plateau. As the largest earthquake to occur around the Laxiongcuo-gaerkong (LGF) fault zone, the occurrence of the 2024 Nima earthquake offers an important chance to further understand the distribution and kinetic characteristic of the seismogenic structures in this little studied region. Methods: In this paper, we use the ascending and descending SAR images of the Sentinel-1A satellite to acquire the coseismic surface deformation related to this event and investigate the seismogenic fault structure. Results and conclusions: Though both the NE-dipping and NW-dipping rupture fault models acquired by InSAR observations can fit the coseismic deformation well, we conclude that this earthquake nucleated a NE-dipping (a strike angle of 325°) right-lateral strike-slip fault with a dip of 83°, which may be a blind branch fault belonging to the LGF, according to the integrated analysis of the inversions, historical earthquakes, regional fault distributions and kinematics. In addition, coseismic coulomb stress changes reveal that the stress at the shallow part of the western segment of the middle branch fault of the XBF can reach 0.11 bar, indicating a high rupture risk.

     

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