Numerical Simulation of the Contribution of the Longmenshan Fault to the Uplift Mechanism of Tibetan Plateau

Tibet Plateau is bordered to the east by the Longmen Shan Fault, adjacent to Sichuan Basin of the stable Yangtze Block. Across the Longmen Shan Fault zone, the topographic differential extends to 5 km, with the deep lithosphere varying by nearly 20 km. In contrast to the large strike-slip faults found within the plateau, the Longmen Shan Fault is an oblique thrust fault that shapes the plateau's boundary, enveloped in a more intricate structural and dynamic environment. The role of the Longmen Shan Fault remains a pivotal point in the ongoing debate regarding the formation of the Tibet Plateau. We have developed a two-dimensional viscoelastic finite element model, encompassing the Longmen Shan Fault, the Tibet Plateau, and the Sichuan Basin on either side. The model simulates, over geological timescales, the thickening process of the Tibet Plateau and the activity of the Longmen Shan Fault under the influence of gravity and the pushing of the Indian plate. The results demonstrate the adjusting role of the Longmen Shan Thrust Fault in the deformation pattern at the eastern edge of the plateau, explaining the difference in the topographic and lithosphere thickness between the Tibet and Sichan Basin. The thrust Longmen Shan Fault not only contributes to cumulative crustal thickening but also plays a role in the thickening of the mid-lower crust and upper mantle viscoelastic media on the Tibet Plateau side.