Understanding the Rupture Kinematics and Slip Model of the 2021 Mw 7.4 Maduo Earthquake: a Bilateral Event on Bifurcating Faults

Abstract

We image the rupture process of the 2021 Mw 7.4 Maduo, Tibet earthquake using slowness-enhanced back-projection and joint finite fault inversion, which combines teleseismic broadband body waves, long-period (166-333 s) seismic waves, and 3D ground displacements from radar satellites. The results reveal a left-lateral strike-slip rupture, propagating bilaterally on a 160-km-long north-dipping sub-vertical fault system that bifurcates near its east end. About 80% of the total seismic moment occurs on the asperities shallower than 10 km, with a peak slip of 5.7 m. To simultaneously match the observed long-period seismic waves and static displacements, notable deep slip is required, despite a tradeoff with the rigidity of the shallow crust. This coseismic deep slip within the ductile middle crust could result from strain localization and dynamic weakening. Local crustal structure and synthetic long-period Earth response for Tibet earthquakes thus deserve further investigation. The WNW branch ruptures ~75 km at ~2.7 km/s, while the ESE branch ruptures ~85 km at ~3 km/s, though super-shear rupture propagation possibly occurs during the ESE propagation from 12 s to 20 s. Synthetic back-projection tests confirm overall sub-shear rupture speeds and reveal a previously undocumented limitation caused by the signal interference between two bilateral branches. The stress analysis on the forks of the fault demonstrates that the pre-compression inclination, rupture speed, and branching angle could explain the branching behavior on the eastern fork.

The overall-subshear and multi-segment rupture of the 2023 Mw7.8 Kahramanmaraş, Turkey earthquake in millennia supercycle

“…The High-Freq radiators imaged by SEBP show an overall subshear northeast rupture process consistent with the FFI slip model, with an average propagation speed of ~3.05 km/s. The first 80 km of the southwest rupture is only partially imaged by SEBP and is obscured by the strong northeast front; this interference is expected when the separation distance between radiators of a bilateral rupture is shorter than the BP resolution 13 . The interference of the bilateral fronts also slightly affects BP imaging between −80 and −150 km, during which the slip in FFI appears 1-5 s earlier than High-Freq radiators.…”

Space Geodetic Insights to the Dramatic Stress Rotation Induced by the February 2023 Turkey‐Syria Earthquake Doublet

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“…Simulated annealing inversions frequently exhibit slight dependence on the chosen random seeds, mainly when multiple optimal solutions exist within the model space, exhibiting indistinguishable objective function values 44 . Moreover, the varying random seeds result in distinct initial fault models and Markov chains.…”