Objectives As the youngest intra-land Cenozoic resurrected orogenic belt, the Tianshan region exhibits intricate tectonic deformation and frequent seismic activities, rendering it as a natural laboratory for investigating continental dynamics. Since the Cenozoic, the tectonic deformation of the Tianshan region has been closely associated with the collision between the Indian and Eurasian plates and the subsequent compressional processes. However, how the compressive stresses generated at the plate boundary are transmitted to the Tianshan remains controversial, and the specific roles played by the Pamir Plateau and the Tarim Basin in the deformation of the Tianshan region have yet to be clearly elucidated. Numerical simulations are arrived out to obtain stress accumulation patterns of major faults in the Tianshan region. By conducting numerical simulation experiments with individually loaded blocks, we aim to analyze the respective roles of the Pamir Plateau and the Tarim Basin in the tectonic evolution of the Southwest Tianshan.

Methods We construct a three‑dimensional elastic‑viscoelastic finite element model of the Southwest Tianshan by incorporating GPS observations as a constraint and considering the prominent active faults and layered lithospheric structure. Based on the finite element model, we simulate the crustal deformation field, the principal strain rate within the region, as well as stress accumulation rates of major active faults and their corresponding Coulomb stress change rates.

Results The simulated crustal deformation field shows good agreement with GPS observations, with the root mean square error of 1.5 mm/a for the east‑west component and 3.2 mm/a for the north‑south component. Overall, deformation of the study region is dominated by north‑south shortening, with the largest deformation occurring in the Pamir Plateau, reaching approximately 20 mm/a. Deformation within the Tianshan region gradually decreases from south to north and is ultimately reduced to 2-5 mm/a due to the mechanical impediment of the Northern Kazakh Platform and the Junggar Basin. The simulation results indicate that the stress field in the Tianshan orogenic belt is dominated by the principal compressive stress in north‑south direction, and the average strain rate inside the Southwest Tianshan orogenic belt is 3.5×10^-8/a. The Keping, Maidan, and Nalati faults exhibit high rates of stress accumulation, indicating a significant likelihood of future strong earthquakes. Notably, the western section of the Keping fault demonstrates the most rapid increase in Coulomb stress, reaching up to 1.5 kPa/a. The results of individually thrusting experiments reveal that the tectonic deformation of the Tianshan region to the east of the junction between the Tarim Basin and the Pamir Plateau is primarily influenced by a combined extrusion force exerted by these two blocks. The Tianshan orogenic belt to the west of the junction is predominantly influenced by the extrusion of the Pamir Plateau, while the Tarim Basin plays a limited role.

Conclusions Through numerical simulations, we quantitatively derive the stress accumulation patterns of the major faults in the Tianshan region and reveal the potential dynamic mechanism underlying convergent deformation in the Southwest Tianshan. It can provide robust support for future seismic risk assessment of this area.