Geodetic modelling of the 2022Mw 6.6 Menyuan earthquake: insight into the strain-partitioned northern Qilian Shan fault system and implications for regional tectonics and seismic hazards

Abstract

Summary Strain partitioning between strike-slip faults in mountains and thrust faults in the foreland is a typical mountain building process to accommodate oblique plate convergence. Studying the geometry and movement of such strain-partitioned fault systems is key to understanding the mountain building process and related seismic hazards. The 2022 Mw 6.6 Menyuan earthquake is the largest strike-slip earthquake to have ruptured the northern Qilian Shan fault system in the modern geodetic era. We combined satellite and field observations to determine the fault geometry and coseismic slip distribution in the Menyuan earthquake, and link the distribution of coseismic slip with the pattern of interseismic strain accumulation within the northern Qilian Shan from our geodetic slip model. We find that the Menyuan earthquake ruptured a 25 km-long section of the left-lateral Longlongling Fault (LLLF) between the surface and 7 km depth. The maximum slip was 4 m at 3–4 km depth. Damage to a high-speed railway tunnel recorded a fault offset of 2.7 m at a depth of 200 m compared to 2.5–3.0 m on the surface, suggesting that dispersion of the rupture through unconsolidated shallow sediments was limited, at least at the tunnel site. We also determined the pattern of interseismic deformation prior to the earthquake using Interferometric Synthetic Aperture Radar (InSAR) and Global Navigation Satellite System (GNSS) data. We found the interseismic geodetic data can be explained by the oblique movement of a low-angle décollement beneath the Qilian Shan rather than a strain partitioning fault system. We suggested that the strike-slip faults and foreland thrusts are separated by a creeping décollement, which would act as a barrier to stop the cascading rupture of the strike-slip and thrust fault.

Strain Partitioning and Fault Kinematics in the Northern Qilian Shan (NE Tibet) Determined From Bayesian Inference of Geodetic Data

“…The data (InSAR, GNSS, leveling data) and synthetic modeling script used in this paper have been shared on Zenodo (Y. Zhang, Chen et al., 2023; Y. Zhang, Wimpenny et al., 2023). The Flower2D code is available from the Github (Daout, 2023).…”

“…In this study, we consider the northern Qilian Shan strain-partitioned fault system, which consists of north-vergent thrusts and ∼E-W trending strike-slip faults that accommodate the oblique convergence between the Gobi Alashan and the Qilian Shan (Figure 1; Allen et al, 2017;Daout et al, 2017;Luo & Wang, 2022). These faults have ruptured in recent destructive earthquakes (Guo et al, 2020;Y. Zhang, Chen et al, 2023; Y.…”

“…Zhang, Chen et al, 2023; Y. Zhang, Wimpenny et al, 2023). Paleo-earthquake research indicates that multi-fault ruptures that span the strike-slip and thrust faults have also occurred on this fault system in the past and may even repeat every ∼4,000 years (Gao et al, 2022;Z.…”

“…In this study, we consider the northern Qilian Shan strain‐partitioned fault system, which consists of north‐vergent thrusts and ∼E‐W trending strike‐slip faults that accommodate the oblique convergence between the Gobi Alashan and the Qilian Shan (Figure 1; Allen et al., 2017; Daout et al., 2017; Luo & Wang, 2022). These faults have ruptured in recent destructive earthquakes (Guo et al., 2020; Y. Zhang et al., 2020; Y. Zhang, Chen et al., 2023; Y. Zhang, Wimpenny et al., 2023). Paleo‐earthquake research indicates that multi‐fault ruptures that span the strike‐slip and thrust faults have also occurred on this fault system in the past and may even repeat every ∼4,000 years (Gao et al., 2022; Z. Li et al., 2022).…”

The 2022 Menyuan Mw6.7 Earthquake Triggered by 2016 M6.4 Earthquake and Stress Transfer on Surrounding Fault Systems in NE margin of Tibetan Plateau, China

“…For this earthquake, dozens of slip models have been published, including models constrained by InSAR (Zhang et al 2023), GNSS , strong motion data and detailed field mapping (Pan et al 2022) and so on. In this study, we selected two variable slip models from published documentation (Li et al 2022a;Li et al 2022b) for 2016 Menyuan M6.4 and 2022 Mw6.7 earthquake, and a third model from personal communication with for the 2022 Menyuan Mw6.7 earthquake.…”