Crustal Motion of Chinese Mainland and Preparation of MS8.0 Wenchuan Earthquake in Sichuan Province

We calculated the moving velocities in Chinese mainland for 1999~2007 years and dynamic moving velocities for 2004~2007 years according to the data from Crustal Movement Observation Network of China. We calculated the activity parameters of Longmenshan fault zone based on the parameters of Qinghai-Tibet and South China subplates, studied the change of the motion field of Chinese mainland, and analyzed the relations between the characteristics of the motion field of the crust and the Wenchuan MS8.0 earthquake. The research revealed that the present-day crustal motion zoning is basically consistent with the geological neotectonic units, indicating that the recent crustal tectonic activity is the inheritance from and development of the neotectonic movement; The dynamic force of crustal motion of Chinese mainland is mainly associated with the action caused by the mutual collision and underthrust of India plate, and Pacific plate to the Eurasia plate. The MS8.0 Wenchuan earthquake is mainly due to the lateral motion caused by the northward pushing of India plate to Qinghai-Xizang subplate, resulting in that Longmenshan fault is compressed to accumulate energy for the MS8.0 Wenchuan earthquake. The crustal dynamic motion in the period of 2004~2007 strengthened the strike slip of Longmenshan fault zone and it transformed from the stable state of compressive strain accumulation to an easy active state under shear force.