Abstract: The 2008 Wenchuan 8.0 earthquake occurred on the eastern boundary of the active Tibet block, and is another strong earthquake in the Tibet block after the 2001 Kunlun 8.1 earthquake. Based on the characters of the structure of crust and mantle and the deep or shallow geological background in the Longmenshan dip fault, this paper constructs a simplified source model of the Wenchuan earthquake, from which dynamic equations from this model are constructed and analytic expressions of stress and strain in the progress of seismogeny are derived. Referring to the geological deformation in the Longmenshan region, we further discuss the process of the Wenchuan earthquake by the analytic solution of the model. The result shows that the process of seismogeny may endure about 3200 years and is very slow and longer because of the lower geological deformation in the Longmenshan region.

Key words: Wenchuan 8.0 earthquake, Geodynamic cause, Seismogenic model