Folding Growth Pattern of the Southern Tian Shan: Insights from the 2024 Mw 7.0 Wushi Earthquake and 2020 Mw 6.0 Jiashi Earthquake, Western China

Abstract The 2024 Mw 7.0 Wushi and 2020 Mw 6.0 Jiashi earthquakes, two recent large events in the southern Tian Shan, provide rare opportunities for understanding the seismotectonic deformation patterns in compressional orogenic regimes. Here, we utilize Sentinel-1 satellite radar images and Differential Interferometric Synthetic Aperture Radar techniques to map coseismic deformation fields for the 2024 Wushi and 2020 Jiashi earthquakes, occurring at the front and root of the Kepingtage fold-and-thrust belt, respectively. A modified Bayesian nonlinear method is utilized to simultaneously invert fault geometry parameters and slip distributions. Our findings show that both Wushi and Jiashi earthquakes are predominantly characterized by reverse/thrust motions with minor strike-slip components. The spatial continuity of the interferometric fringes and coseismic deformation fields suggests shallow (<5 km depth) folding deformation in response to deeper reverse/thrust faulting. Specifically, the Wushi earthquake produced a high-angle fault-propagation fold, with fault-slip penetrating into the crystalline basement, whereas the Jiashi earthquake formed a low-angle detachment fold developed within the cover layer. The Mw 5.7 aftershock following the Wushi mainshock compensated for the shallow coseismic slip deficit and generated positive flowerlike ruptures superimposed on the pre-existing mainshock fold deformation, explaining the observed opposite dip direction of the aftershock rupture compared to the mainshock mechanism. These two fold-type earthquakes demonstrate the dominance of folding deformation in accommodating crustal shortening and orogenic growth in the southern Tian Shan, elucidating compressional tectonic processes.