Abstract: On the basis of previous study of the 1679 Sanhe-Pinggu(M8.0)earthquake,which is the biggest event in history ever recorded in Beijing and its adjacent area,we performed a 3-D strong ground motion simulation by utilizing staggered-grid finite difference method to study the distributions of peak ground velocity with different earthquake source models in Beijing region.In the paper,earthquake source models and a transmission medium velocity model are established and the corresponding parameters are given with the accordance to the results from related previous study.Then,using a three-dimensional finite difference computing program of near-fault strong ground motion developed by Graves,the peak ground velocity caused by the destructive earthquake in Beijing area is simulated.In our computation model,the earthquake source is 3km in depth,and a total number of 21,679 observation points on the ground surface is figured out.The transmission medium velocity model is composed of four stratums which are the Quaternary deposit,the upper crust,the upper part of the middle crust and the lower part of the middle crust.With the minimum grid spacing of 0.15km,a total of 2.28?10⁶ grids are generated.Using a time step of 0.02 seconds we calculated the peak ground velocity for 8 seconds duration time.After the analysis of the simulation results,we observed some basic characteristics of near-fault strong ground motion such as near-fault concentration effect of peak ground velocity,rupture directivity effect,hanging wall effect,and basin effect.The results from our simulation and analysis suggest that the source and transmitting medium parameters in our model are suitable and the finite difference method is applicable to estimate the distribution of strong ground motion in the study region.

Key words: strong ground motion, source parameter, transmitting medium parameter, concentration effect, rupture directivity effect, hanging wall effect, basin effect

摘要： 文中利用1679年三河-平谷8级地震的有关资料和北京地区地下三维结构的研究成果,建立了相应的震源模型和传播介质模型.利用Graves的三维有限差分程序,计算了北京地区震后的地面峰值速度.通过对计算结果的分析处理,获得了近断层强地震动的近断层效应、方向性效应、上盘效应和盆地效应等基本特征.同时,这些特征也反映了我们所设定的震源和传播介质参数的合理性,以及模拟方法的正确性.另外,分析处理中所获得的这些结果可为北京地区的城市规划和抗震设防提供客观的参考依据.

关键词: 强地震动, 震源参数, 介质参数, 近断层效应, 方向性效应, 上盘效应, 盆地效应