QUASI-STATIC DEFORMATION ACCOMPANIED BY PROPA-GATION OF FAULT CREEP--A THEORETICAL MODEL ANALYSIS AND DISCUSSION ON THE CHARACTERI- STICS OF EARTHQUAKE FAULT MOVEMENT BEFORE THE 1976 TANGSHAN EARTHQUAKE

According to the geodetic data and the results from laboratory experimentation, as well as the precursory features of some earthquakes, in this paper a fault creep propagation model is given. The model simulates an extension of the dislocation surface along the fault belt in viscoelastic half-space. For studying the features of deformation nearby the belt, the analytical expressions for quasi-static deformation due to the creep propagation is derived and the author has obtained the theoretical fields of the displacement by the aid of numerical integration. In calculation, the material is taken to be the generalized Kelvin substance and we presume that the slip-time function is △U = B(1-e-t/T) and the creep events propagate unilaterally or bilaterally along the fault.With reference to the results from the model and by analysing the short period geodetic data observed in the stations along Candong fault belt before the 1976 Tangshan earthquake, an inversion of the development of the fault motion is made. It can be demonstrated that the obvious propagation of creep occurred along the belt and the initial creep source appears between the Xiao2han station and the Canzhou station. Then, the creep event propagated from this location to the northeast and south west directions along the belt, and the dislocation at the south west side of the initial creep source is right-lateral strike-slip, the dislocation at the northeast side is the same as above described, but with less compressional dip-slip component.