1)Institute of Geology, CEA, Beijing 1000292)Institute of Earthquake Science, CEA, Beijing 1000363)First Crust Monitoring and Application Center, CEA, Tianjin 300180
Abstract：On the analysis of deformation information reflected by GPS velocity data in different reference, the difference between movement and deformation is discussed and we emphasize the deformation is independent from reference basis. On the basis of reliability analysis of GPS strain rate calculation results with least square collocation method, the evolution characteristics of GPS strain rate fields are discussed in different spatial scale. The eastwest strain rate fields shows that the area in west to 92°E has a EW stretch and the area in the east to 92°E has an EW compression in QinghaiTibet block. This character reflects the eastward flow of the material of QinghiaTibet plateau is barred by NorthChina and SouthChina Blocks and forms a spatial span of 900km compression zone, that the strain rate results of 3 sections shows the high compression zone locating at the middle area of SouthNorth seismic zone. The strain rate result in SichuanYunnan illustrates that the eastward movement of Bayankala block lead to the surface strain concentrating in the source of Wenchuan eartqhake, and the eastwest compression deformation becomes more intensive in Longmenshan faults while the high area of eastwest compression transferring to east. The evolution result of rotation rate fields shows that the anticlockwise deformation is weaken in the south of Longmenshan fault and the clockwise deformation has been strengthened in the north of Longmenshan fault from 2004 to 2007. The distribution of principal strain rate changing from disheveled to consistent reveals that the locking status of Longmenshan fault has reached highpoint with the compression and dextrorotation deformation strengthening.
Wu Yanqiang,Jiang Zaisen ,Yang Guohua et al. EVOLUTION CHARACTERISTICS OF STRAIN RATE FIELD REFLECTEDBY GPS DATA BEFORE WENCHAUN EARTHQUAKE[J]. jgg, 2011, 31(5): 20-25.
