The Characteristics of Present-day Crustal Deformation in Western China and Discussion of Its Mechanism

Based upon re measurement data about 400 GPS stations obtained in last decades in Chinese Mainland and her adjacent area, the images of present day horizontal crustal movement and deformation have been formed. The results indicate, that there is only a little shorten (5 mm/a or so) about SN direction in western part of the Qinghai Tibet plateau, however no shorten evidence is discovered in its eastern part; that constriction in SN direction mostly took place in Ximalaya belt of the south edge which is in the plateau, the magnitude is about 15 mm/a, and the same directional variance happened in the west of Qaidam in the middle of the north edge in the plateau and in the Tianshan area which locates north of the plateau also in its adjacent region, the magnitude is about 15 mm/a too; that there is about 10 mm/a extension in EW direction in Qinghai Tibet plateau; that the eastward movement in east edge of the western China is stronger in south and weaker in north; that the rhombic Sichuan Yunnan Block is not a escape block but a deformation block; that the east edge of the Tibet plateau and its vicinity are decline areas in east direction; the surface strain results show that the constriction is found at the edge around the Qinghai Tibet plateau, surface expanded in its interior and constriction with 10E -8 /a in the north part of Western China.The squeezing in north direction from the India plate can not explain the deformation results. According to the latest geophysical results, we consider the mantle substantial inrush under crust may be another dynamical source that control Tibet plateau motion even the deformation of Chinese Mainland, which perhaps was dominant dynamical source.