A numerical study of contemporary crustal deformation partitioning across the Southwestern Tian Shan orogen

The Tian Shan region is a typical example of crustal deformation within an intracontinental environment, where the lithospheric rheological properties are marked by significant spatial heterogeneity. However, the role of lithospheric rheology in crustal strain partitioning within the interior of the Tian Shan orogenic belt remains nebulous. Here, we utilized a two-dimensional viscoplastic model with contact elements constrained by GPS velocities and fault slip rates to investigate the influence of the block's strength on crustal deformation in the southwestern Tian Shan region. Our founding suggests that a weaker lower crust beneath the northern Tian Shan region offers a potential mechanism for the contemporary deformation patterns. Contemporary crustal deformation at Tian Shan is mainly concentrated along the piedmont thrust-and-fold belts and diffuses in the orogen's interior. This pattern of crustal strain partitioning is closely linked to the interplay between fault slips and lithospheric deformation. This finding emphasizes the significant role that the lithospheric rheology and pre-existing faults played in the deformation partitioning in the interior of the Tian Shan orogeny.