基于InSAR约束的2020年中国西藏定日MW5.7地震同震滑动模型

doi:10.12196/j.issn.1000-3274.2022.02.011

摘要/Abstract

摘要： 2020年3月20日, 中国西藏定日县发生M_W5.7地震, 稀缺的区域地震地质资料给认识发震构造带来诸多不便。为准确认识此次地震的破裂机制, 本文首先利用DInSAR技术对Sentinel1-A升轨和降轨数据进行处理, 采用GACOS模型做大气改正, 获得LOS同震形变场。然后将地震简化为一个具有均匀滑动量的有限矩形, 采用非线性反演算法研究均匀滑动模型, 以便确定发震断层的位置及其几何参数。最后基于上述结果, 构建同震破裂几何模型, 反演同震破裂滑动分布。结果表明, 发震断层的走向330°, 倾角51°。此次地震的破裂相对集中, 主要分布在深度2.32~5.31 km范围内。破裂区长约5.6 km, 宽约3.6 km。最大滑动量约1.13 m, 位于87.4102°E, 28.6691°N处, 埋深3.967 km。破裂以正断滑动为主兼具部分右旋走滑分量, 平均滑动角-106.6°。释放的地震矩为3.89×10¹⁷ N·m, 对应的矩震级为M_W5.7。印度板块向北东方向挤压欧亚板块, 在定日地区产生近东西向的拉张力, 使得该地区正断层发育, 这可能控制着该地区的地震类型。

关键词: 青藏高原, 2020年定日M_W5.7地震, InSAR同震形变, 均匀滑动, 滑动分布

Abstract: The 20 March 2020 M_W5.7 Dingri earthquake occurred at southern Qinghai-Xizang Plateau. Scarce regional seismic geological data have brought a lot of inconvenience to the understanding of the earthquake-generating structure. In order to resolve these rupture parameters, DInSAR technology is used to process Sentinel1-A ascending and descending orbit data, and the GACOS model is used for atmospheric correction to obtain the LOS coseismic deformation. We utilized the near-field displacements to investigate the uniform slip model by a nonlinear inversion method in order to resolve the fault location and its geometrical parameters. Then, based on these results, the slip distribution of the earthquake was inversed. We conclude that the 2020 Dingri earthquake occurred on an east-dipping blind normal fault with a dip of ~51°. Strike of the fault was ~51°. The slip mainly confined between ~2.32 and 5.31 km depth and the peak slip was ~1.13 m, which occurred at a depth of ~3.967 km. The slip was predominantly normal-sip with slight right-lateral strike-slip components, releasing a total seismic moment of 3.89×10¹⁷ N·m, corresponding moment magnitude was M_W5.7. This study holds that the Indian plate compresses the Eurasian plate to the northeast and produces a nearly E-W tensile force in Dingri area, which makes the normal faults develop and controls the earthquake types in this area.

Key words: The Qinghai-Xizang Plateau, The 2020 Dingri M_W5.7 earthquake, InSAR coseismic deformation, Uniform slip, Slip distribution

中图分类号:

P315.7

肖雁峰, 胡晓斌, 谭凯. 基于InSAR约束的2020年中国西藏定日M_W5.7地震同震滑动模型[J]. 地震, 2022, 42(2): 140-148.

XIAO Yan-feng, HU Xiao-bin, TAN Kai. Study on the Coseismic Slip Model of the 2020 Dingri M_W5.7 Earthquake in Xizang, China Constrained by InSAR Measurements[J]. EARTHQUAKE, 2022, 42(2): 140-148.

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