Research on deformation characteristics of the 2021 Qinghai Maduo MS7.4 earthquake through coseismic dislocation inversion

Abstract

Over the past 70 years, the Qinghai Maduo Ms7.4 earthquake (May 22, 2021) has been the only earthquake with a magnitude of ≥7 that has occurred within the Bayan Har Block. To investigate the deformation process of this earthquake, we acquired the Interferometric Synthetic Aperture Radar (InSAR) coseismic deformation field based on Sentinel-1 SAR images, which showed that the maximum line of sight (LOS) displacement was ~1 m. By combining this information with the results of our field investigation, the fault slip distributions were obtained by inversion using the single- and double-fault models, wherein the latter model showed better inversion results than that of the former. According to the inversion results, the overall rupture pattern was predominantly left-lateral strike-slip, with a released seismic moment of ~Mw7.5. Specifically, the principal seismogenic fault had a strike of 283°, dip of 91°, and maximum slip of 4.87 m; the branch fault along the eastern segment of the rupture had a strike of 110°, dip of 94°, and maximum slip of 2 m. Conversely, the results derived from the Global Navigation Satellite System (GNSS) strain rate field before the earthquake indicated that the Maduo earthquake occurred in East Kunlun,which is characterized by the largest maximum shear strain rate. The strain accumulation rate (~2.5 × 10−8/yr) was significantly lower than that of the Xianshuihe fault zone on the southern boundary of the Bayan Har block and the East Kunlun fault zone on its northern boundary. Furthermore, pre-seismic deformation near the seismogenic fault was relatively gentle, showing partial late seismogenic characteristics.