Abstract <p>Accurately characterizing the activity of large-scale deep faults in the western Tibetan Plateau is essential for understanding the dynamic mechanisms driving the uplift and outward expansion of the plateau. In this study, we focus on the Longmu Co segment of the Longmu Co-Dulishihu Fault (LDF), a sinistral strike-slip fault that separates the Qiangtang Block from the Tianshuihai Block. Previous research has provided limited understanding of the activity of this fault. Through detailed field investigations, unmanned aerial vehicle (UAV) surveys, and trench excavations, we constrain the paleoseismic events recorded in the trenches. Using AMS ¹⁴C dating to establish chronological constraints on faulting, we identify two paleoseismic events (Event I–II), which are constrained to the intervals of 10–7.8 and 3–0.7 ka respectively, with an inferred earthquake recurrence interval of less than 5 ka. Combined with geomorphic analysis and cosmogenic nuclide (¹⁰Be) exposure dating, we estimate the late Quaternary horizontal slip rate of the Longmu Co segment to be 0.7–1.3 mm/a. The vertical slip rate is estimated to be 0.04 ± 0.01 and 0.16 ± 0.01 mm/a, based on offsets of river terraces and scarps, respectively. However, additional data are required for further analysis. Integrating these results with previously reported tectonic activity rates from other faults in the western Tibetan Plateau, we suggest that the Tianshuihai Block exhibits a hybrid deformation model, with the associated faults accommodating part of the regional strain. The paleoseismic history and slip rates presented in this study provide important insights into the late Quaternary deformation and spatial deformation patterns of the western Tibetan Plateau.</p>