关键词: 玛多7.4级地震, Burgers流变模型, 同震库伦应力, 黏弹性库伦应力

Abstract: The seismogenic fault of the Madoi Ms7.4 earthquake on May 22, 2021 is not the tradition north boundary of the Bayan Har Block, instead a secondary fault in the Bayan Har Block is nearly parallel to the main fault of the East Kunlun fault. As a result, the study on the stress effect of the Madoi earthquake on the peripheral faults, especially main boundary of the Bayan Har Block, is urgent. In this paper, the lithospheric structure of the study area is stratified by using the USTClitho1.0 results of the unified seismic velocity model of the lithosphere in Chinese mainland. The coseismic slip model of the Madoi earthquake is inversed by the results of InSAR deformation field and precise aftershock location. By considering the burgers rheological model which is more consistent with the actual deformation process of lithosphere, the paper calculates the coseismic and post-earthquake viscoelastic coulomb stresses in the source area and peripheral faults caused by the Madoi earthquake by using PSGRN/PSCMP program. The results show, except the fracture surface of the seismogenic fault, there are three positive coulomb stress areas on the West and East ends of the fracture fault, in which the coulomb stress loading areas on the west end is toward the northwest of the fracture fault, and there are two coulomb stress loading areas at the east end, which are toward the north and east of the fracture fault. The positive value of coseismic coulomb stress of peripheral faults is consistent with that of source area. The triggering of coseismic coulomb stress on the near source section of East Kunlun fault, the east section of Kunzhong fault, the northwest segment of Gande southern fault and the middle segment of Wudaoliang-Changshagongma fault, of Madoi earthquake is greater than 0.01 MPa. In addition, the viscoelastic relaxation of lithosphere after the Madoi earthquake further increases the viscoelastic coulomb stress of the above faults, so we should pay more attention to the seismic risk of the above faults in the future.

Key words: Madoi Ms7.4 earthquake, Burgers rheological model, coseismic coulomb stress, viscoelastic coulomb stress