1679年三河-平谷8级地震近断层强地震动的有限元模拟

SIMULATIONS OF THE NEAR-FAULT STRONG GROUND MOTION OF THE 1679 SANHE-PINGGU M 8 EARTHQUAKE

文中通过收集整理三河-平谷8级地震的历史记录、野外地质调查和区域地震等资料,建立了该地震的震源模型;以穿过研究区的12条测线和区域第四纪、新近纪、古近纪沉积等厚度图等资料为基础,建立了北京地区的传播介质模型;利用哈尔滨工程力学研究所的近断层强地震动有限元程序和40节点的高性能并行计算机计算了北京地区震后60s内地表各点的地震动速度时程和峰值速度。为检验模拟结果的质量,我们取2排测点的速度时程和水平向峰值速度等值线图进行了分析,发现计算结果与历史地震记录及实际地震观测资料吻合良好,说明了我们的模拟结果的可信性和模拟方法的客观性。

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 4928 0.5km x 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.