Horizontal crustal movement in Chinese mainland before and after the great Kunlun Mountain M=8.1 earthquake in 2001

The continuous GPS observation at the fiducial stations in the Crustal Movement Observation Network of China(CMONOC) recorded the crustal movement of Chinese mainland before and after the great Kunlun Mountainearthquake of M=8.1 on November 14, 2001, especially the horizontal crustal movement in the western part ofChina. Based on the datum defined by a group of stable stations with small mutual horizontal displacements for afew years, the time series of horizontal displacements at fiducial stations were obtained. Significant anomaloushorizontal displacements had appeared at the fiducial stations in the western part of China since early November2000 and several earthquakes with the magnitudes about 6.0 had occurred in Yunnan and Sichuan Provinces. Thenorthward components of the horizontal displacement at the fiducial stations in west China had decreased signifi-cantly and even changed in the opposite sense since mid April 2001. After the earthquake, the northward dis-placements still decreased and there were significant westward displacements. The process of the crustal move-ment in the western part of Chinese mainland (in reference to east China) suggests that the main force source forthis earthquake came from the northward pushing of the Indian plate. The great earthquake released a large amountof energy, as a result, the action applied by the Indian plate to Chinese mainland diminished significantly and afterthe great earthquake, the seismic activity in Chinese mainland decreased considerably until the end of 2002.