Lower friction of the Xianshuihe-Xiaojiang fault system and its effect on active deformation around the south-eastern Tibetan margin

We use three-dimensional mechanical modelling with fault as Coulomb-type frictional surface to explore the active deformation of the Xianshuihe-Xiaojiang fault system in south-eastern Tibet. Crustal rheology is simplified as an elastoplastic upper crust and a viscoelastic lower crust. Far-field GPS velocities and Quaternary fault slip rates are used to constrain the model results. Numerical experiments show that effective fault friction lower than similar to 0.1-0.08 leads to a high slip rate that fits well with geological estimates of the slip rate on the fault system. Associating with the modelled fault slip rate, strain in the surrounding crust distributes broadly, and is partitioned into strike-slip and thrust senses. This means that in the Indian-Eurasia convergence, accommodation of the large fraction of sinistral motion on the fault system is achieved mainly due to its lower fault friction. This in turn affects crustal deformation around the south-eastern Tibetan margin, resulting in negligible compression across the Longmen Shan.