Resolving co- and early post-seismic slip variations of the 2021 MW 7.4 Maduo earthquake in east Bayan Har block with a block-wide distributed deformation mode from satellite synthetic aperture radar data

Abstract

On 21 May 2021 (UTC), an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau. The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since the 2008 Wenchuan earthquake and in proximity to the seismic gaps on the east Kunlun fault. Here we use satellite interferometric synthetic aperture radar data and subpixel offset observations along the range directions to characterize the coseismic deformation of the earthquake. Rang offset displacements depict clear surface ruptures with a total length of ~170 km involving two possible activated fault segments in the earthquake. Coseismic modeling results indicate that the earthquake is dominated by left-lateral strike-slip motions of up to 7 m within top 12 km of the crust. The well-resolved slip variations are characterized by five major slip patches along strike and 64% of shallow slip deficit, suggesting a young seismogenic structure. Spatial-temporal changes of postseismic deformation are mapped from the early 6-day and 24-day InSAR observations, and are well explained by time-dependent afterslip models. Analysis of GPS velocity profiles and strain rates suggests that the eastward extrusion of plateau is diffusely distributed across the east Bayan Har block, but showing significant lateral heterogeneities as evidenced by magnetotelluric observations. The block-wide distributed deformation of the east Bayan Har block along with the significant co- and post-seismic stress loading from the Maduo earthquake imply high seismic risks on regional faults, especially the Tuosuo Lake and Maqin-Maqu segments of the Kunlun fault that known as seismic gaps.