Source Process Featuring Asymmetric Rupture Velocities of the 2021 Mw 7.4 Maduo, China, Earthquake from Teleseismic and Geodetic Data

Abstract

Abstract On 21 May 2021, an Mw 7.4 left-lateral strike-slip earthquake occurred within the Bayan Har block in the Tibetan plateau. To learn about the source rupture process, we collected the teleseismic waveforms and utilized the backprojection method to investigate the rupture kinematics of the earthquake. The results indicate that the earthquake was a bilateral rupture event with asymmetric rupture velocities. The rupture velocity in the east of the epicenter was uniform and in the range of 2.72–3.67 km/s, whereas, in the west, it was in the range of 1.39–1.78 km/s in the first 20 km and then increased to 2.82–3.17 km/s. The slip distribution constrained by the Interferometric Synthetic Aperture Radar and Global Positioning System displacements clearly reveals kinematic coseismic slip in greater detail, which makes up for the limitations of the backprojection method. Two main asperities in the east verify the results of the backprojection method. The rupture depth in the west was slightly shallower than that in the east, which may be the reason for the asymmetry of rupture velocities. The initial rupture point was updated based on the asymmetric velocities and geodetic slip distribution. The multiple-point-source moment tensors based on the rupture velocities and new initial rupture point not only match the fault geometries determined by relocated aftershocks but also fit well with the released energy distribution, which proves the asymmetry of rupture velocities.