2021年青海玛多MS7.4地震同震应力场与形变台站同震阶变分布关系探讨

Discussion on the Relationship between the Co-seismic Stress Field and the Distribution Co-seismic Step among Deformation Observation Stations from the Maduo MS7.4 Earthquake

摘要:

利用基于升、降轨InSAR形变场及余震精定位结果反演得到的同震滑动模型,通过PSGRN/PSCMP程序获得同震水平形变场及应力场分布特征,结合玛多M_S7.4地震周边形变同震阶变台站分布特征,探讨同震应力场变化与同震阶变台站分布间的关系。模拟得到的水平形变场结果显示,此次玛多地震为左旋走滑运动特征,水平形变量主要集中在巴颜喀拉块体内,其次是北部的柴达木块体;羌塘块体以及祁连块体同震水平位移量较小;昆仑山口-江错断裂作为一条NE倾向的走滑型断裂,断层上盘区域滑动量明显大于下盘,模拟得到的最大水平形变量达1380mm;形变同震阶变的台站主要集中分布在祁连山断裂带中东段以及西秦岭等地区,祁连山断裂带中东段位于此次玛多地震同震正应力变化正值区域,而西秦岭等地区则处于玛多地震同震剪切应力变化的正值区域,即出现同震阶变的台站与同震应力场变化的正值区域具有较好的一致性。

Abstract:

In this paper,the co-seismic slip model inversed by the results of InSAR deformation field and precise aftershock location is used to study Maduo M_S7.4 earthquake. The distribution characteristics of co-seismic horizontal deformation field and local stress field are obtained by PSGRN/PSCMP program. Combined with the distribution of deformation stations with co-seismic step around Maduo earthquake,the relationship between the variation of co-seismic stress field and the co-seismic step among deformation stations is discussed. The simulated horizontal deformation field shows that the Maduo earthquake is characterized by the sinistral-strike slip movement. The large horizontal displacements are mainly concentrated in the block of Bayan Har block,followed by the Qaidam block in the north,and the co-seismic horizontal displacement in Qiangtang block and Qilian block is quite small. Kunlun Shankou-Jiangcuo fault is a NE trending strike slip fault. The slip amount in the hanging wall of the fault is significantly greater than that in the footwall,and the maximum horizontal deformation obtained by simulation is about 1380mm. The deformation stations with co-seismic step are mainly distributed in the middle-east section of Qilian Fault zone and west Qinling Mountains area. The Middle-east section of Qilian Fault zone is located in the positive area of co-seismic normal stress variation of Maduo earthquake,while the west Qinling Mountains are located in the positive area of co-seismic shear stress variation of Maduo earthquake,that shows,the deformation stations with co-seismic step have good consistency with the positive area of co-seismic stress field variation.