Present day crustal vertical movement inferred from precise leveling data in eastern margin of Tibetan Plateau

We collect precise leveling data observed in the period of 1970 to 2012 around the eastern margin of the Tibetan Plateau, and process the data to acquire present day crustal vertical velocity field. Vertical rates of 9 GPS sites are employed as a priori constraints to define the reference frame. The velocity field shows that most of the regions in the eastern margin of the Tibetan Plateau are undergoing uplift. The Gongga Shan and West Qinling are uplifting at maximum rates of 5.8 +/- 1.0 mm/a and 6.0 +/- 13 mm/a, respectively. A 2-D buried dislocation model is used to infer normal or reverse dip-slip rates. The result indicates that the reverse slip rate along the Longmen Shan fault is 4.2 +/- 0.5 mm/a, followed by the Daliangshan and Longriba faults with the rates of 3.7 +/- 0.5 mm/a and 2.8 +/- 0.3 mm/a respectively. TheZemuhe and northern section of the Xiaojiang fault have the normal slip rates of 2.3 +/- 1.0 mm/a and 2.9 +/- 0.4 mm/a respectively. Combining vertical velocity field with GPS derived horizontal velocity field, we investigate the characteristics of crustal movement and dynamic mechanism. The 3D velocity field indicates that the Helan Shan is uplifting and the Yinchuan graben is subsiding. The 3D crustal movement of the Liupan Shan region is segmented, with the area in the vicinity of the northern Liupan Shan fault uplifting and the area in the vicinity of southern Liupan Shan fault subsiding respectively. The subsidence of the central and southern Sichuan-Yunnan terrain is caused by the near east-west extension. The budget of horizontal material influx suggests that movements of the upper and lower crust are rather different in most of the region, excessive material influx into the lower crust/upper mantle underneath most of the sub-blocks seems required to maintain the uplift rates inferred from leveling, providing evidence for the existence of lower crustal flow in this region. (C) 2014 Elsevier B.V. All rights reserved.