关键词: 强地震动, 右旋走滑正断层, 传播介质模型, 并行计算, 峰值速度, 方向性效应, 盆地效应

Abstract: On the basis of previous study of the 1679 Sanhe-Pinggu(M 8.0)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 explicit and decoupled finite element method to study the velocity history of ground point and the distributions of peak ground velocity in Beijing region.In the paper,earthquake source models of 1679 Sanhe-Pinggu(M8.0)earthquake are established and the corresponding parameters are given according to the data from history records,field geologic surveys,the study of regional earthquakes and empirical correlation.Meanwhile,by using the twelve profiles and sediment contour maps of Quaternary and Tertiary deposits in the study area,we established the transmission medium model.Then,applying a three-dimensional finite element computing program of near-fault strong ground motion and parallel computation technique developed by the Institute of Engineering Mechanics,China Earthquake Administration,the peak ground velocity and the velocity history of 32,400 observation points on the ground surface in Beijing area are simulated.In our computation model,the earthquake source is 3km in depth and composed of 49280.5km?0.5km grids.The transmission medium model comprises thirty-six different character parts.With the grid spacing of 0.08km,a total of 2.187?10⁷ grids are generated.Using a time step of 0.005 seconds we calculated the peak ground velocity and velocity history of observation points for 60 seconds duration time.In order to verify the simulation result,we selected and analyzed twenty-four velocity histories of observation points which were along two beelines and a contour map of horizontal peak ground velocity.After the analysis of the simulation results,we found the results are well in accordance with the historical records of the 1679 Sanhe-Pinggu(M 8.0)earthquake and the characteristics of near-fault strong ground motion,which were observed in the great earthquakes.The results from our simulation and analysis suggest that the source parameters and transmission medium parameters in our model are suitable and the explicit and decoupled finite element method is applicable to estimate the distribution of strong ground motion in the study region.

Key words: strong ground motion, right-lateral normal fault, transmission medium model, parallel computation, peak ground velocity, rupture directivity effect, basin effect