Abstract: On the basis of elastic rebound theory, using horizontal velocity field of mainland China calculated from GPS data during three observation periods from 1999 to 2007, velocity components that parallel with and plumb to the fault zone are calculated respectively in different period, and then relative ground movements of two sides of the fault zone are analysed with power function fitting and graphics. The results show that, the relative ground movement shows right-lateral shear deformation before the Wenchuan 8. 0 earthquake. At the same time, the movement had been locked at the Longmenshan fault zone. So the results have a positive significance for distinguishing elastic strain energy accumulation and deformation anomaly of earthquake preparation, and for further research on earthquake prediction.

Key words: Seismotectonics, GPS, Elastic strain, Longmenshan fault zone, The Wenchuan 8. 0 earthquake