TY - JOUR

T1 - Mechanism and implications of the post-seismic deformation following the 2021 Mw 7.4 Maduo (Tibet) earthquake

AU - Chen, Fei

AU - Diao, Faqi

AU - Haghighi, Mahmud Haghshenas

AU - Wang, Yuebing

AU - Zhu, Yage

AU - Wang, Rongjiang

AU - Xiong, Xiong

N1 - Funding Information: This work was supported by the National Key Research and Development Program of China (Grant No. 2022YFF0800703, 2023YFC3007302). We thank Yanqiang Wu and Yan Hu for support in GPS data collection. We thank Thomas R. Walter and Mahdi Motagh for their assistance in the InSAR data processing. We also thank the Editor Ana Ferreira and Reviewer Jihong Liu and one anonymous reviewer for their valuable comments. The figures were drawn using the Generic Mapping Tools (GMT) software (Wessel & Smith ).

PY - 2024/4

Y1 - 2024/4

N2 - 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.

AB - 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.

KW - friction of fault zones

KW - Numerical modelling

KW - Rheology

KW - Satellite geodesy

KW - Time-series analysis

UR - http://www.scopus.com/inward/record.url?scp=85184854883&partnerID=8YFLogxK

U2 - 10.1093/gji/ggae034

DO - 10.1093/gji/ggae034

M3 - Article

AN - SCOPUS:85184854883

VL - 237

SP - 203

EP - 216

JO - Geophysical journal international

JF - Geophysical journal international

SN - 0956-540X

IS - 1

ER -