Mechanism and implications of the post-seismic deformation following the 2021 M_w 7.4 Maduo (Tibet) earthquake

authored by

Fei Chen, Faqi Diao, Mahmud Haghshenas Haghighi, Yuebing Wang, Yage Zhu, Rongjiang Wang, Xiong Xiong

Abstract

A major earthquake shook the Chinese county of Maduo, located in the Songpan-Ganzi terrane on the Tibetan Plateau, on 21 May 2021. Here, we investigate the post-seismic deformation process of this event, with the aim to understand the fault geometry, friction behaviour and regional rheology. To keep the self-consistency between co- and post-seismic deformation models, we first constrain the fault geometry and coseismic slip model of this event, which are directly used in modelling the post-seismic deformation. The coseimsic slip model reveals that the majority of coseismic slip is confined at the middle (3–15 km) of the brittle layer, leading to significant shallow slip deficit. Secondly, we obtain the post-seismic deformation in the first 450 d following the 2021 Maduo earthquake using the GPS and InSAR displacement time-series data. Thirdly, a combined model incorporating afterslip and viscoelastic relaxation is built to explain the observed post-seismic deformation. Our results suggest that the viscoelastic relaxation effect should be considered in the observation period, in order to avoid the unphysical deep afterslip in the ductile lower crustal layer. Combined analysis on viscosities inferred from this study and previous studies suggests a weak lower crust with steady-state viscosity of 10¹⁸–10¹⁹ Pa s beneath the Songpan-Ganzi terrane, which may give rise to the distributed shear deformation and the development of subparallel secondary faults within the terrane. Besides, the inferred afterslip on uppermost patches of the middle fault segment suggests a rate-strengthening frictional behaviour that may be related to the coseismic slip deficit and rupture arrest of the Maduo earthquake.

Organisation(s)

Institute of Photogrammetry and GeoInformation (IPI)

External Organisation(s)

China University of Geosciences
China Earthquake Administration (CEA)

Type

Article

Journal

Geophysical journal international

Volume

237

Pages

203-216

No. of pages

14

ISSN

0956-540X

Publication date

04.2024

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Geophysics, Geochemistry and Petrology

Electronic version(s)

https://doi.org/10.1093/gji/ggae034 (Access: Open)