Coseismic Deformation Field and Fault Slip Distribution Inversion of the 2020 Jiashi Ms 6.4 Earthquake: Considering the Atmospheric Effect with Sentinel-1 Data Interferometry

Abstract

Due to some limitations associated with the atmospheric residual phase in Sentinel-1 data interferometry during the Jiashi earthquake, the detailed spatial distribution of the line-of-sight (LOS) surface deformation field is still not fully understood. This study, therefore, proposes an inversion method of coseismic deformation field and fault slip distribution, taking atmospheric effect into account to address this issue. First, an improved inverse distance weighted (IDW) interpolation tropospheric decomposition model is utilised to accurately estimate the turbulence component in tropospheric delay. Using the joint constraints of the corrected deformation fields, the geometric parameters of the seismogenic fault and the distribution of coseismic slip are then inverted. The findings show that the coseismic deformation field (long axis strike was nearly east–west) was distributed along the Kalpingtag fault and the Ozgertaou fault, and the earthquake was found to occur in the low dip thrust nappe structural belt at the subduction interface of the block. Correspondingly, the slip model further revealed that the slips were concentrated at depths between 10 and 20 km, with a maximum slip of 0.34 m. Accordingly, the seismic magnitude of the earthquake was estimated to be Ms 6.06. Considering the geological structure in the earthquake region and the fault source parameters, we infer that the Kepingtag reverse fault is responsible for the earthquake, and the improved IDW interpolation tropospheric decomposition model can perform atmospheric correction more effectively, which is also beneficial for the source parameter inversion of the Jiashi earthquake.

InSAR coseismic deformation field and seismogenic structure of the 2020 Mw6.0 Jiashi earthquake and the implication for the moderate-magnitude seismicity in the southwestern Tian Shan, western China

“…In addition, the right-lateral displacement, with a maximum of ~0.025 m, is significantly smaller than the vertical deformation, (Figures 4G, H). The coseismic displacement in horizontal direction has been neglected in previous studies (Yao et al, 2020;Yu et al, 2020;He et al, 2021a;Yao et al, 2021;Zhang et al, 2021;Wang et al, 2022;Zhang et al, 2023), but the observed horizontal displacement in this study demonstrates that the strikeslip motion is partially accommodated by the fold-and-thrust belts at the southern frontal margins of the Tian Shan except for the highangle active faults within the mountain ranges (Wu et al, 2023).…”

“…The coseismic deformation field reveals that the deformation area is mainly distributed in the southern margin of the Kepingtage FTB and covers two important thrust faults, the Keping fault and Ozigertau fault (Yao et al, 2020;Yu et al, 2020;He et al, 2021b;Yao et al, 2021;Wang et al, 2022;Zhang et al, 2023). The surface uplift area is primarily located between the Keping fault and the Ozigertau fault, and the subsidence area is largely distributed on the northern side of the Ozigertau fault and partially on the southern side.…”

“…Given the determined geometric parameters of the fault, the slip distribution on the fault plane was linearly related to the deformation data, allowing for a solution through linear inversion, the linear observation equation can be expressed as (Zhang et al, 2023):…”

“…The seismic sequences and relocated aftershocks reveal a more complex thrust event, with deep basement-involved slips beneath the decollement (He et al, 2021a;Yao et al, 2021). Most studies suggest that the seismogenic structure of the Jiashi earthquake is the Keping thrust in the south leading edge of the Kepingtage FTB (Yao et al, 2020;Yu et al, 2020;He et al, 2021b;Yao et al, 2021;Zhang et al, 2021;Zhang et al, 2023). However, few studies reveal how surface deformation responds to deep coseismic slip (Yao et al, 2020;He et al, 2021a).…”

“…The Keping thrust, the south leading thrust of the Kepingtage FTB, is deemed to be the seismogenic structure of the 2020 Mw6.0 Jiashi earthquake (Figure 1) (Yao et al, 2020;Yu et al, 2020;He et al, 2021b;Yao et al, 2021;Zhang et al, 2021;Wang et al, 2022;Zhang et al, 2023). The thrust fault has roughly east-west orientation and a length of ~460 km.…”