Late Quaternary tectonic activity characteristics of the western Qiulitage thrust fault, southwestern Tianshan, China

The western Qiulitage thrust fault is one of the most active structures in the western Tianshan, playing a key role in accommodating crustal shortening in the Tianshan orogen. This study quantifies the Late Quaternary activity of this fault using remote sensing interpretation, field investigation, UAV surveying, and OSL dating. The results robustly confirm that the western Qiulitage thrust fault has been active since the Late Quaternary, and has experienced multiple surface-rupturing strong earthquakes, which have produced prominent vertical dislocations ranging from 0.39 ± 0.09 to 6.9 ± 0.17 m. Monte Carlo simulations show the average crustal shortening rate over the past 5.0 ka BP is 1.35 ± 0.16 mm/a, which represents its long-term deformation rate since the Late Quaternary. This activity indicates that tectonic deformation in southwestern Tianshan is not entirely concentrated within the young thrust fault‑anticline belt at the nappe front; instead, faults in the interior and root zone of the Tianshan also accommodate a significant portion of the regional tectonic deformation.