Geodetic Constraints on Fault Kinematics and Dynamics of 2021 Maduo Earthquake: Implications for Fault Friction

Postseismic afterslip has been inferred to occur on fault barriers surrounding coseismic asperities, which can be explained by velocity-strengthening friction in barriers and velocity-weakening friction in asperities. However, afterslip also exhibits spatial overlap with coseismic slip for some events. Here we use ∼2 years of Sentinel-1 interferometric synthetic aperture radar (InSAR) data to study the postseismic deformation following the 2021 Mw 7.4 Maduo earthquake. Additionally, we use ∼7 years of InSAR data to generate the interseismic velocity and remove the interseismic contributions from postseismic data. We observe localized postseismic creep in the middle segment of the seismogenic fault, and distributed deformation in far field. We first apply a kinematic inversion to model the afterslip and find significant overlap between afterslip and coseismic slip on fault shallow region. We then conduct dynamic earthquake cycle simulations with vertical variations of friction to understand the conditions required for this to occur. Numerical models suggest that shallow part with velocity-strengthening properties can rupture seismically and creep during postseismic and interseismic periods. Our dynamic model partially explains the overlapping slip of the Maduo earthquake. However, the required shallow interseismic creep is not seen through detailed analysis of the interseismic velocity, implying that creep is either absent or too low to be observed. Our work enhances the understanding of fault friction control on fault slip during the earthquake cycle.