Present-Day Tectonic Activities of Transverse Faults in the Keping Region, Southwest Tianshan

Abstract The Keping fold-and-thrust belt (KFB), situated at the southern front of the Tianshan orogenic belt, represents a typical thin-skinned imbricated structure resulting from the uplift and southward-thrusting orogeny of the Tianshan. The KFB is believed to accommodate a considerable portion of the north–south convergence of crustal shortening and thickening across the Tianshan, making it an ideal region for investigating intracontinental orogenic processes. In this study, we used four ascending tracks and two descending tracks of the Sentinel-1 A/B data collected over six years to construct Interferometric Synthetic Aperture Radar (InSAR) line-of-sight velocity fields. Subsequently, the 3D interseismic velocity of the KFB was determined by integrating Global Positioning System and InSAR observations. Finally, we employed 2D edge dislocation models to quantify the kinematic parameters of the folds in the western KFB constrained by the vertical velocities. Our results indicate that the western KFB exhibits a crustal shortening rate of 6.3–7.8 mm/yr, which accounts for approximately one-third of the north–south shortening rate observed in the Tianshan orogenic belt. Among the fault zones, the West Keping fault at the thrust front exhibits the highest slip rate, with slip rates increasing from east to west. The maximum crustal shortening rate in the western segment reaches 3.6 mm/yr, constituting half of the total shortening within the KFB. Combined with topographical and geomorphological studies, we propose that the intensity of the southwestward-propagating orogeny from the Tianshan toward the KFB may have diminished.