Coseismic deformation analysis of the 2021 Qinghai Madoi M7. 4 earthquake

The Madoi M7. 4 earthquake occurred on May 22, 2021, in Madoi County, Qinghai Province. It is located at similar to 70 km south of the East Kunlun fault zone on the northern boundary of the Bayan Har block. So it belongs to the intra-block fault zone earthquake. According to the data provided by the China Continental Tectonic Environment Monitoring Network, 25 cm permanent east-west displacement is recorded at the Madoi Station, which is more than 30 km away from the epicenter. Meanwhile, the InSAR also observes obvious deformation field, with the maximum relative LOS (Line of Sight) of ascending and descending about 1. 87 m and 2. 32 m, respectively. In order to interpret these geodetic observation data, we use seismic dislocation theory of different Earth models based on three fault slip models to calculate the coseismic deformation field and compare results with GNSS observation and InSAR LOS deformation. The result indicates the displacement field generated by the fault slip model which is inversed by InSAR data is good agreement with the theoretical calculation with the spherical earth model. Furthermore, we use the better fault model to calculate the theoretical coseismic displacement, geoid, gravity and strain changes of the 2021 Qinghai Madoi M7. 4 earthquake. The results provide a theoretical basis for GNSS and gravity observation interpretation of Madoi earthquake.