Crustal Motion Characteristics in the Eastern Margin of the Tibetan Plateau and Adjacent Regions after the Wenchuan Earthquake

The Wenchuan earthquake has altered the crustal motion characteristics in the eastern margin of the Tibetan Plateau and adjacent regions. Using discontinuous GPS survey data for 2008 2012, the velocity field for the Eurasia reference framework has been obtained, and the general trend of contemporary crustal motion after the occurrence of the Wenchuan earthquake has been studied. In addition, using the velocity field, the block movement velocity has been estimated by least-squares fitting. Furthermore, the properties and displacement rates of main faults have been obtained from the differences in velocity vectors of the blocks on both sides of the faults. The results reveal that there are no obvious changes in the general characteristics of crustal motion in this area after the Wenchuan earthquake. The earthquake mainly changed the rate of the movement of the Chuan-Qing block and caused variation in the movement direction of the South China block. The effect of the earthquake on faults is mainly reflected in variations in fault displacement velocity; there is no fundamental change in the properties of fault activity. The displacement rates of the Xianshuihe fault decreased by 3-4 mm/a, the Longmenshan fault increased by 9-10 mm/a, and the northern segment of the Anninghe fault increased by approximately 9 mm/a. Furthermore, the displacement rates of the Minjiang, Xueshan, Huya, Longquanshan, and Xinjin faults increased by 2-3 mm/a. This implies that the effects of the Wenchuan earthquake on crustal movement can mainly be observed in the Chuan-Qing, South China, and N-Chuan-Dian blocks and their internal faults, as well as the Xianshuihe and Longmenshan faults and the northern section of the Anninghe fault. The reason for this is that the Wenchuan earthquake disturbed the kinematic and dynamic balance in the region.