Large‐Scale Crustal Deformation, Slip‐Rate Variation, and Strain Distribution Along the Kunlun Fault (Tibet) From Sentinel‐1 InSAR Observations (2015–2020)

Abstract

Large‐scale geodetic measurements of crustal deformation in the north‐central Tibetan Plateau are crucial for improved understanding of earthquake‐cycle processes and long‐term seismic hazard assessment. We use GPS velocities and Interferometric Synthetic Aperture Radar (InSAR) observations (2015–2020) on eight descending and eight ascending Sentinel‐1 tracks to map surface motions and their gradients for an area of over ∼2,000 km × 350 km around the Kunlun‐Manyi fault system. The derived line‐of‐sight (LOS) and 3D velocity fields demonstrate ongoing postseismic transients along the ruptured segments of the 1997 Manyi and 2001 Kokoxili earthquakes, interseismic deformation along locked fault segments, and strain accumulation on a large subsidiary fault (i.e., the Kunlun Pass fault). We use elastic dislocation and analytical postseismic deformation models constrained by our dense InSAR measurements to quantify the interseismic and postseismic contributions, which reveal the along‐fault distribution of fault slip rate and locking depth along the entire length of the fault. The results indicate that the slip rate of the Kunlun fault systematically decreases toward the west to the west of the Taiyang Lake fault. We also find that the interseismic strain accumulation rate along the main trace of the Kunlun fault is to first‐order spatially constant (0.1–0.15 microstrain/yr), except around its restraining bend. As the historically unruptured segments, especially the eastern segments (from 95°E to 101°E) of the Kunlun fault, have relatively fast slip rates and high locking depths (>15 km), they have the potential to generate large and damaging earthquakes in this region.

Increased Water Content in the Active Layer Revealed by Regional‐Scale InSAR and Independent Component Analysis on the Central Qinghai‐Tibet Plateau

“…(2021); D. Zhao et al. (2022). The cluster‐like ground subsidence may be attributed to the thawing of ice‐rich permafrost (J. Chen et al., 2022).…”

An Updated Fault Coupling Model Along Major Block‐Bounding Faults on the Eastern and Northeastern Tibetan Plateau From a Stress‐Constrained Inversion of GPS and InSAR Data

“…For InSAR data sets in Zhao et al. (2022a), the postseismic deformation during the InSAR observation period excited by the 2001 Mw7.8 Kokoxili earthquake has been corrected using the combined afterslip and viscoelastic relaxation model in Zhao et al. (2021), which is constrained by the postseismic observations during 2001–2010.…”

“…Before further including InSAR data of the Xianshuihe fault, we need to separate the transient deformation using earthquake-cycle models, which is beyond our scope in this study. The InSAR data sets from Zhao et al (2022a) and Ou et al (2022) comprise the mean velocity field along both descending and ascending tracks, while the InSAR measurements from Fang et al (2022) are the decomposed east-west component from descending and ascending observations (see the detailed method in Fang et al, 2022). All InSAR data sets span 2015-2020 or 2015-2021, which do not contain the deformation from the most recent large earthquake in the region, for example, the 2021 Mw7.4 Maduo earthquake (e.g., Fang et al, 2022;Yue et al, 2022).…”

“…The involvement of the Kunlun Pass fault in the 2001 Kokoxili earthquake motivates us to include this large subsidiary fault of the Kunlun fault to examine the fault coupling over our observation period (e.g., Lasserre et al., 2005). In the interior of the plateau, for instance, the Kunlun fault, the lateral resolution of coupling is limited mainly by sparse GPS data (e.g., Zhu et al., 2021), whereas this problem can be overcome by adding spatially dense InSAR measurements (e.g., Zhao et al., 2022a). Different from previous widely‐used elastic block models (e.g., McCaffrey et al., 2002; Meade & Hager, 2005; Meade & Loveless, 2009), we adopt a physical constraint based on a stress‐constrained inversion method, with a new consideration of stress interactions between each isolated faults (e.g., Bürgmann et al., 2005; Johnson & Fukuda, 2010; Lindsey et al., 2021).…”

Transient fault creep on the Xidatan (Tibet) fault driven by viscoelastic relaxation following the 2001 Kokoxili earthquake

“…Due to the nearly east-west trend of the Xidatan fault, the dominant contribution to the resultant fault-parallel velocities is from east-west displacements generated by the left-lateral strike-slip motion of the fault. Red (Liu et al, 2019) and blue (Wang and Shen, 2020) Zhao et al, 2022), the estimates of fault coupling ratio likely provide a lower bound in Zhu et al (2021). Some narrow stripes of low coupling from top to bottom around the Xidatan fault in (a-c) are not kinematically reliable due to the sparse GPS data constraints on the surface.…”