IMPACT OF LARGE-SCALE FAULTING ON THE SURFACE DEFORMATION OF INDIA-EURASIA COLLISION INFERRED FROM 3-D VISCOUS MODELING (Invited Presentation)

A key topic of contention involving continental deformation revolves around the relative importance of discrete faulting or distributed strain on the accommodation of observed deformation in the continental lithosphere. We use 3-D lithospheric, Stokes flow simulations of the India-Eurasia (IN-EU) collision zone to investigate the effect of large-scale lithospheric faults on surface deformation and derive allowable bounds for fault strength and spatial scale. Lithospheric strength is constrained by laterally-varying, lithospheric-average effective viscosities and partitioned vertically to capture strength anomalies corresponding to geophysically-imaged slabs and weak Tibetan lower crust. Finite zones of low viscosity are introduced representing major fault systems of the IN-EU collision zone: the Karakorum, Altyn-Tagh, Kunlun, Jinsha Suture-Xianshuihe, Jiali-Red River, and Sagaing. We find (1) narrow zones of lithospheric scale weakness in conjunction with a weak lower crust are important for reproducing rotation in Southeast Tibet and (2) cases with finite zones of weakness representing large-scale faults produce focused uplift at the Longmen Shan and extension across southern Tibet and thickening in northeastern Tibet consistent with observations.