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This study focuses on the crustal deformation and interseismic fault coupling along the strike-slip Kunlun fault, northern Tibet, whose western segment ruptured in the 2001 Mw 7.8 Kokoxili earthquake. We first integrated published Global Positioning System (GPS) velocity solutions and calculated strain rate fields covering the Kunlun fault. Our results show abnormally high post-earthquake strain rate values across the ruptures; furthermore, these exceed those in pre-earthquake data. Together with two tracks of interferometric synthetic aperture radar (InSAR) observations (2003–2010) and position time-series data from two continuous GPS sites, we show that the postseismic deformation of the Kokoxili earthquake may continue up to 2014; and that the postseismic transients of the earthquake affect the 2001–2014 GPS velocity solutions. We then processed the GPS data observed in 2014–2017 and obtained a dense interseismic velocity field for the northern Tibet. Using a fault dislocation model in a Bayesian framework, we estimated the slip rates and fault coupling on the Kunlun fault in 1991–2001 and 2014–2017. Results show an increase of slip rates and eastward migration of high fault coupling on the Kunlun fault after 2001. We propose the temporal variations are a result of the eastward accelerating movement, as a whole, of the Bayanhar block, whose boundaries were decoupled by several large earthquakes since 1997. Moreover, our results show the accumulated elastic strains along the Alake Lake-Tuosuo Lake segments could be balanced by an Mw 7.4–7.7 earthquake. [ABSTRACT FROM AUTHOR]

Normal faulting in orogens is usually associated with gravitational potential energy (GPE) due to elevation differences and contrasting material rheology between mountains and foreland areas. The 2008–2020 Yutian normal earthquake sequence in the West Kunlun Mountains has been closely studied over the last decade, but the mechanisms of normal faulting in the region are still an open question as both gravitational force and releasing step-overs have been proposed to explain the extension in West Kunlun. We investigated the normal faulting mechanism through (1) co- and postseismic kinematic models constrained by interferometric synthetic aperture radar (InSAR) and (2) analytical force balance modeling with a thin viscous approximation. We used the InSAR time series technique to map the postseismic deformation within 3 years following the 2008 Yutian earthquake. The InSAR-derived afterslip model revealed a clear slip polarity transition from strike-slip to normal faulting, suggesting a tight connection between the normal faulting and bounding strike-slip faults. The global navigation satellite system (GNSS)-constrained thin viscous sheet model gave an estimate of ~1022 Pa∙s for the effective viscosity of the West Kunlun lithosphere, which is generally in line with previous estimates that used a similar methodology. The stress field predicted by the thin viscous model primarily features north–south compression rather than east–west extension, suggesting that normal faulting is caused not by the GPE contrast across the margin of West Kunlun, but instead by the releasing step-overs bounded by strike-slip faults. The main contribution of this paper is therefore identifying the primary causes of normal faulting in West Kunlun and improving our understanding of the active tectonics of the NW Tibetan Plateau. • The postseismic InSAR time series following the 2008 Mw 7.1 Yutian earthquake is presented. • The slip transition from strike-slip to normal faulting was revealed by slip models. • Extension in West Kunlun is due to releasing step-overs rather than gravitational force. [ABSTRACT FROM AUTHOR]