Fault geometry and low frictional control of the near-field postseismic deformation of the 2021 Mw 7.3 Maduo earthquake

Abstract

The 2021 Maduo earthquake caused ∼160 km-long complex coseismic surface rupture and postseismic deformation. However, the afterslip pattern and primary reason for the overlapped coseismic slip and afterslip in shallow portion in Maduo earthquake are still unclear. Here, we used ∼0.85 yr Sentinel-1 data to obtain the time-dependent postseismic deformation of the 2021 Mw 7.3 Maduo earthquake and inverted afterslip distribution. We calculated the frictional parameter of the seismogenic fault based on the time series afterslip and depicted the rupture surface based on three-dimensional coseismic displacement. Our findings indicated that the more considerable postseismic deformation in the near-field was concentrated on the bending region near the epicenter. The maximum afterslip was ∼0.35 m in the shallow upper crust. The shallow afterslip overlapped with the coseismic rupture, mainly caused by the low frictional parameter (a – b = 0.002) and shear heating in the shallow region. The fault geometry was gentle in the supershear rupture area, while changed substantially in the west of the epicenter. This highlights that the fault bending could have controlled both coseismic and postseismic deformation pattern in near-field. It also indicates that fault bending controls the stress propagation for large strike-slip fault, which provides a new perspective for seismic risk assessment of other strike-slip faults in the Bayan Har block.