Abstract: The Maduo M_S7.4 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_S7.4 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.

Key words: Maduo earthquake, coseismic deformation, finite element model, Coulomb stress change, seismic hazard