2021 Qinghai Madoi M(w)7. 4 earthquake coseismic deformation field and fault-slip distribution using GNSS observations

On May 22, 2021, a M(w)7. 4 event stroke Qinghai Madoi in Bayan Har massif, attracting attention on the seismic activities in this area. Based on a campaign-mode observation after the event and data from the regional continuous GNSS stations, this paper obtained coseismic displacements of the Madoi earthquake in 106 GNSS sites and high-frequency seismic waveforms in 17 continuous GNSS sites of them. The GNSS coseismic displacement field shows that the Madoi earthquake is a typical left-lateral strike-slip event and the maximum coseismic displacement observed by GNSS is 1.2 m. GNSS and InSAR observations are consistent with each other and the details of near-field deformation can be shown by the GNSS observation. Based on the GNSS coseismic displacements, we carried out an inversion for the coseismic slip distribution of the Madoi earthquake and then calculated the Coulomb stress changes on the seismogenic fault induced by the event. The inversion results show that there are several asperities on the fault, and the fault ruptured to the ground surface. The results are consistent with field surface rupture report and aftershock distribution. Coseismic slip is concentrated at the depth of 0 similar to 10 km, and the maximum slip is up to 4.6 m. The inverted seismic moment is 1.63 X 10(20) N . m, corresponding to M(w)7. 4. Areas of increased Coulomb stress roughly cover aftershock distributions, demonstrating that aftershocks were mainly triggered by the load of static Coulomb stress.