李水平, 陈刚, 何平, 丁开华, 陈云锅, 王琪. 2015年尼泊尔地震同震滑动及震后余滑的三角位错模型反演[J]. 武汉大学学报 ( 信息科学版), 2019, 44(12): 1787-1796. DOI: 10.13203/j.whugis20180128
引用本文: 李水平, 陈刚, 何平, 丁开华, 陈云锅, 王琪. 2015年尼泊尔地震同震滑动及震后余滑的三角位错模型反演[J]. 武汉大学学报 ( 信息科学版), 2019, 44(12): 1787-1796. DOI: 10.13203/j.whugis20180128
LI Shuiping, CHEN Gang, HE Ping, DING Kaihua, CHEN Yunguo, WANG Qi. Inversion for Coseismic Slip Distribution and Afterslip of the 2015 Nepal Mw 7.9 Earthquake Using Angular Dislocations[J]. Geomatics and Information Science of Wuhan University, 2019, 44(12): 1787-1796. DOI: 10.13203/j.whugis20180128
Citation: LI Shuiping, CHEN Gang, HE Ping, DING Kaihua, CHEN Yunguo, WANG Qi. Inversion for Coseismic Slip Distribution and Afterslip of the 2015 Nepal Mw 7.9 Earthquake Using Angular Dislocations[J]. Geomatics and Information Science of Wuhan University, 2019, 44(12): 1787-1796. DOI: 10.13203/j.whugis20180128

2015年尼泊尔地震同震滑动及震后余滑的三角位错模型反演

Inversion for Coseismic Slip Distribution and Afterslip of the 2015 Nepal Mw 7.9 Earthquake Using Angular Dislocations

  • 摘要: 2015年尼泊尔Mw 7.9级地震发生在印度板块向欧亚板块低角度俯冲的喜马拉雅断裂带上。对该地震的滑动模型进行精化,对于理解喜马拉雅断裂带的孕震模式具有重要意义。采用三角形位错元构建主喜马拉雅断裂“双断坡”几何模型,联合全球定位系统(Global Positioning System,GPS)和合成孔径雷达干涉测量(interferometric synthetic aperture radar,InSAR)资料反演2015年尼泊尔地震同震滑移及震后余滑。结果表明,尼泊尔地震最大同震滑移达到7.8 m,深度为15 km,位于中地壳断坡和浅层断坪的接触部位。不考虑中地壳断坡结构会使反演的最大滑移量偏低。震后余滑主要分布在同震破裂区北侧,释放的地震矩为1.02×1020 N·m,相当于一次Mw 7.3级地震,约占主震释放地震矩的12%。同震库伦应力变化和震间断层闭锁分布均表明,尼泊尔地震破裂区南部宽约60 km的区域仍具有较高的地震危险性。

     

    Abstract: The 2015 Nepal Mw 7.9 earthquake occurred in the central segment of the Himalayan collision zone where the rigid Indian plate is underthrusted beneath the Tibetan Plateau. Refining the coseismic slip distribution and afterslip of the earthquake has great significance for better understanding the seismogenic mechanism in Himalaya orogenic belt. We adopted the angular dislocation elements to construct the rampflat-ramp-flat fault geometry of the main Himalayan thrust. In combining with GPS and InSAR data, we inverted the coseismic slip distribution and afterslip of the Nepal earthquake. The result shows that the mainshock is dominated by thrust slip with minor right-lateral strike-slip. The maximum slip of the mainshock is up to 7.8 m at a depth of 15 km, near to the intersection between the upper flat and mid-crust ramp. The total geodetic moment based on our preferred slip model is M0=8.39×1020 N·m, corresponding to an Mw of 7.93 assuming a shear modulus of 30 GPa. The released moment is mainly confined to the depth of 15-25 km, in which nearly 50% of the released moment locates at the ramp of upper crust. The maximum slip could be underestimated if we ignore the mid-crust ramp. The inferred afterslip primarily concentrates on the downdip of the coseismic rupture. The afterslip is characterized by pure thrust slip with the maximal amplitude of 0.5 m. The total released moment by the afterslip is estimated to be 1.02×1020 N·m, equivalent to an Mw 7.3 earthquake, approximately 12% of the coseismic moment. The coseismic static Coulomb stress change suggests that the southern part to the rupture zone of the Nepal earthquake with a width of about 60 km is largely promoted by the 2015 Nepal earthquake. Considering the fact that this area is strongly locked during the interseismic period, the near-term seismic hazard in this area deserves special attention.

     

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