Mechanical interactions between the underthrusting Indian crust and overlying Tibetan crust: insight from 2D numerical modeling

The Tibetan Plateau has been characterized by orogen-wide crustal thickening and surface uplift, partially attributed to the underthrusting Indian model. In addition, the underthrusting Indian crust has been proposed to promote the predominant E-W extension and N-S rifting in southern Tibet. However, the influence of the underthrusting processes of the Indian crust on crustal deformation in the Tibetan Plateau remains debated. Here, we construct a series of 2D thermo-mechanical models to investigate the mechanical interactions between the rigid underthrusting Indian lower crust and its overlying Tibetan crust. The preliminary results show that pronounced decrease in N-S compressional rates in the upper crust above the front edge of the underthrusting Indian lower crust, which moves northwards with the northward slab indentation. In contrast, the shear tractions on the overlying upper crust from the interior of the underthrusting plate, alleviating the N-S compression, are relatively slight. Therefore, the numerical results indicate locally accelerated extension in the middle-upper crust of the southern Tibet in response to the northward indentation of the Indian lower crust.