Contemporary Crustal Deformation in Sichuan-Yunnan Region from GPS and Gravity Data

High precision GPS horizontal velocities and gravity data were used to estimate the crustal motion and fault slip rate in Sichuan-Yunnan region(96°-106°E,20°-36°N).Due to the influence of India-Tibet block's east-northward extrusion,and the gravitational buoyancy force associated with the sharp topographic gradient across the region,the first-order features of crustal deformation are the prominent clockwise rotation around East Himalaya Syntax(EHS),and leads left-slip motion along the Xianshuihe-Xiaojiang fault system(east boundary) and right-slip motion along the Jinshajiang-Honghe fault system(west boundary).The Xianshuihe-Anninghe-Zemuhe-Xaiojiang fault system is the most active left-lateral fault in the region,with a rate of 12.1±0.6 mm/a,9.0±1.2 mm/a,6.4±1.0 mm/a,6.0±1.2 mm/a and 9.0±1.2 mm/a respectively.The Longmenshan fault system is with a rate of 2.6±1.1 mm/a right-lateral slip,and 1.3±1.2 mm/a extrude.As a result,the pattern of crustal deformation in the region supports the continuous deformation hypothesis.