Present-day Crustal Movement Of Northeastern Margin Of Tibetan Plateau Constrained By GPS Observations

The crustal movement characteristics of the northeastern margin of Tibetan plateau are studied based on the newest GPS observation, the data is calculated accurately with the GAMIT/GLOBK software, and the horizontal motion velocity fields and the horizontal motion characteristics during 1999-2003 are obtained, then the northeastern margin of Tibet plateau is divided into sub-blocks , and the crustal geodynamics and interaction of the divided sub-blocks are analysised according to the obtained horizontal motion velocity. In order to examine the influence of the Kunlun Ms8.1 earthquake on the crustal motion,the coseismic horizontal displacements of Kunlun Ms8.14 earthquake are calculated using Okada dislocation model,and the effect on local crustal horizontal motion of Kunlun Ms8.1 earthquake are analysised in the end.The main conclusions are:(1)Relative to Eurasia, the GPS motion displacements during 1999-2001 of the Qianlian-Haiyuan Fault zones are well consistented with the geological result: the western part of Qilian fault maily manifests northeastward motion and crustal shortening; the middle and eastern part of Gansu-Qinghai block rotates clock-wisely, and the northern boundary of rotating block is Haiyuan fault; pushed forward by the rotating Gansu-qinghai block, Erdos block takes anti-clockwise rotation;Alashan block is more stabilized than others. (2)Ralative to stable Eurasia, the crustal movements characteristics during 2001-2003 of northeastern margin of Tibetan plateau are: the western part of Gansu-Qinghai block maily manifests south westward motion, and there are differential motion: its south westward motion of the southern part is bigger than that of northern part; the crustal motion velocity of the region in the Delingha-Gonghe-Zhangye is very small; The eastern part of Gansu-Qinghai block(in the east to Xining city) rotates clock-wisely; The boundary of Erdos block mainly takes southward motion.?On the Okada model, the GPS data is calculated. The results shows that the effect of coseismic crustal deformations of Kunlun Ms8.1 earthquake on the motion of northeastern margin of Tibetan plateau is so small that it isn't the main reason to change the block motion.This study is very useful either in correctly acquainting with the crustal change process before and after earthquake, or in studying block motions and establishing mainland China crustal motion geodynamics model. It offens an reliance to the study of mainland China geodynamics.