Fault Source Model and Stress Changes of the 2021 Mw 7.4 Maduo Earthquake, China, Constrained by InSAR and GPS Measurements

Abstract

ABSTRACT On 22 May 2021, an Mw 7.4 earthquake struck Maduo, China, within the eastern Bayan Har block of the Tibetan plateau. The eastward-extruding Bayan Har block is marked by active seismicity along its boundary faults, including the 2008 Mw 7.9 Wenchuan earthquake, but large earthquakes within the block are relatively rare. Thus, the Maduo earthquake could provide useful information about crustal deformation of the Tibetan plateau. Early reports, shortly after the earthquake, have suggested a sinistral strike-slip fault rupture, but the fault geometry and slip distribution vary in these models due to the limited observational constraints. Here, we reconstructed a model of fault geometry and coseismic slip using Interferometric Synthetic Aperture Radar and Global Positioning System data. A nonplanar fault model was constructed based on pixel-offset images and the optimized dip angle. The along-strike variation of the dip angle is small, so a single optimized dip is used. Our results suggest that the Maduo earthquake ruptured ∼156 km on a northwest-striking major fault that dips 78°, and ∼24 km on a minor southeast-striking fault that dips 64°. Most fault slip occurred above 15 km depth, and released a moment of ∼1.65×1020  N·m. Using the resolved fault source model, we calculated the change of coulomb failure stress in the region and on the neighboring faults. The Maduo earthquake highlighted intrablock deformation in the Tibetan plateau whereas numerous lithospheric blocks extrude along major strike-slip faults.