NUMERICAL SIMULATION FOR RUPTURE PROCESSES OF A SERIES OF STRONG EARTHQUAKES ( MS＞7) IN NORTH CHINA SINCE 1966
1966年以来华北地区一系列七级大震破裂过程的数值模拟

The different rupture processes of strong earthquakes (M S=7), such as Xingtai earthquake in 1966, Bohai earthquake in 1969, Haicheng earthquake in 1975, and Tangshan earthquake in 1976, which occurred on the boundary faults of blocks in North China and in the systematic environment of tectonic blocks under mutually restricting, are simulated numerically by discontinuous deformation Analysis (DDA+FEM). In the paper, the results of numerically simulating 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 agree basically with focus mechanism, focus parameters from seismic wave, macroscopic isoseisms and horizontal displacement vector map from observation on surface of earth. Furthermore,the imageof contour picture of maximum shear stress change on orthographically rupture mode of Bohai earthquake in 1966is 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 very suitable tool to simulate rupture process of earthquakes.