2021年5月22日青海玛多M_(S)7.4地震同震变形的数值模拟及其动力学启示

Coseismic deformation of Maduo M_(S)7.4 earthquake in Qinghai,on May 22,2021:numerical simulation analysis and geodynamic enlightenment

2021年5月22日青海玛多M_(S)7.4地震是近年来唯一一次发生在巴颜喀拉块体内部的强震,其同震变形及应力调整受到很多学者的高度关注。采用分裂节点技术研发了一套研究大地震同震变形的三维并行弹性有限元程序,并使用弹性地震位错模型的解析解验证该程序的正确性和有效性。在此基础上,研究2021年5月22日青海玛多M_(S)7.4地震同震变形及研究区域主要断层上的同震库仑应力变化,结果表明:计算得到的地表同震变形与不同大地测量数据和有限断层模型反演得到的结果一致,显示该地震主要为左旋走滑断层,有部分正断层分量;9~11 km深度范围内除主震断层带两侧大于1.0级的余震基本位于10 km深度水平面内平行于主震的库仑应力变化大于零的区域;玛多地震引起不同断裂带上的库仑应力变化的分布是不均匀的,其中鄂拉山断裂南段、昆中断裂东段、东昆仑断裂带的大部分(除中部靠西的小部分外)、玛多—甘德断裂北西段、南东段及主震震中附近、达日断裂带北西段库仑应力增加明显,地震危险性提高,需要密切关注。

The Maduo M_(S)7.4 earthquake in Qinghai on May 22,2021 is the only strong earthquake that occurred in Bayan Har block in recent years.The coseismic deformation and stress adjustment of the Maduo earthquake have been highly concerned by many scholars.In this paper,a three-dimensional parallel elastic finite element program for coseismic deformation simulation of large earthquakes is developed using split node technique.The correctness and effectiveness of the program were verified by comparing with the analytical solutions of the elastic seismic dislocation models.We calculated the coseismic deformation of the Maduo M_(S)7.4 earthquake and the coseismic Coulomb stress changes on the major faults in the research area.The results show that the surface coseismic deformation is consistent with those by different geodetic observation data and inversion results of some finite fault models.It also shows the earthquake is mainly a sinistral strike-slip fault with some normal fault components.Most aftershocks(magnitude>1.0 and depth of 9-11 km)except those besides the mainshock fault located in the regions of positive Coulomb stress changes at the depth of 10 km.The distribution of the Coulomb stress changes on the different fault zones is not uniform.The Coulomb stress changes on the southern end of Elashan Fault zone,the eastern end of Kunzhong Fault zone,most segments except some central-western parts of East Kunlun Fault zone,the northwestern segment of Dari Fault zone and the northwest and southeast segments and regions near the mainshock of Maduo-Gande Fault zone increase obviously,which requires more attention.