1966年以来华北地区一系列七级大震破裂过程的数值模拟

用非连续变形分析方法(DDA+FEM)数值模拟，在华北地区各地块相互制约的块体系统环境中，地块边界断层上发生1966年邢台地震、 1969年渤海地震、 1975年海城地震、 1976年唐山地震等不同类型破裂模式大震的破裂过程. 数值模拟结果给出每个大震释放的主应力场，最大剪应力变化等值线图，地震前后位移变化矢量图，发震断层滑移随时间变化以及走滑错距和应力降等震源参数. 这些结果与地震的震源机制，用地震波资料研究得到的震源参数,宏观等震线,地表观测的水平位移矢量图基本一致. 其中1969年渤海地震正交破裂模式的结果与宏观等震线及小震分布图像更接近. 1976年唐山地震复杂震源模式与该震早期余震分布图像更相符. 表明用DDA+FEM方法进行数值模拟研究，能较好地模拟地震破裂过程.

NUMERICAL SIMULATION FOR RUPTURE PROCESSES OF A SERIES OF STRONG EARTHQUAKES ( MS＞7) IN NORTH CHINA SINCE 1966

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.