Numerical Simulations for Rupture Processes of a Series of Strong Earthquakes (Ms> 7) in North China Since 1966

Abstract The different rupture processes of strong earthquakes of magnitude 7 such as the Xingtai earthquake in 1966, Bohai earthquake in 1969, Haicheng earthquake in 1975, and Tangshan earthquake in1976, which occurred on the boundary faults of blocks in North China in a system of mutually restricting tectonic blocks, are simulated numerically by discontinuous deformation analysis (DDA+FEM). In the paper, the results of numerical simulation include the principal stress field released in every large earthquakes, the contour picture of maximum shear stress change, the vector picture of displacement caused by the earthquakes, the sliding displacement on faults with time, the maximum strike sliding distance and stress drop. These results are in agreement basically with focal mechanisms, focus parameters from seismic waves, macroscopic isoseisms and horizontal displacement vector map from observations on the surface of Earth. Furthermore, the contour image about maximum shear stress change of the orthographical rupture mode of Bohai earthquake in 1969 is closer with the macroscopic isoseismal picture. The results about the complex focus of Tangshan earthquake in 1976 are more accordant with aftershock distribution picture at early period of the earthquake. It is indicated that DDA+FEM is a suitable tool to simulate rupture process of earthquakes.