北京地区高风险断裂及其强地面运动模拟

北京地区历史上发生多次破坏性地震.在未来50年超越概率10%的中国地震烈度区划中，北京地区烈度为Ⅷ度.北京邻区强震对北京地震烈度的影响已经有一些研究.然而，如果北京地区的断裂发生强震，其地震烈度将有多大？又是如何分布？这是防震减灾所关注的问题.北京活断层研究表明，黄庄—高丽营等断裂具有第四纪分段活动特征.本文首先用有限元方法对北京地区活动地震断裂地震安全度进行评估，确定了黄庄—高丽营断裂（北段）是其中地震安全度相对最低的断裂；然后在此断裂上设定一个M_S7.2的情景地震，使用可以考虑真实起伏地形影响的任意曲线网格有限差分方法模拟了这个设定地震在北京地区引起的强地面运动特征和烈度分布细节.强地面运动模拟结果表明，峰值速度PGV>0.7 m·s^-1的区域集中在沿断裂东侧的8~9 km宽的条带内，最大值达1 m·s^-1；烈度分布显示断裂周围20 km内大都超过Ⅷ度.本文结果可为防震减灾提供参考依据.

High-risk fault and strong ground motion simulation in Beijing area

Beijing area has experienced several destructive earthquakes throughout its history. In the seismic zonation map with 10% exceeding probability in the next 50 years, the seismic intensity is Ⅷ in Beijing area. The impact of strong earthquakes in neighboring areas on the seismic intensity of Beijing has been studied to some extent. However, if a strong earthquake occurs on a fault in Beijing area, what will be the magnitude of the seismic intensity and how will it be distributed? These are very important questions for earthquake prevention and disaster reduction. Studies on active faults in Beijing area show that the Huangzhuang-Gaoliying fault and other faults have characteristics of Quaternary segmental activity. In this paper, we first evaluate the seismic safety of active earthquake faults in Beijing area using the finite element method and determine that the northern segment of Huangzhuang-Gaoliying fault has relatively low seismic safety. Then, a scenario earthquake with MS7.2 is set on this fault, and the arbitrary curved grid finite difference method, which can consider the influence of real topography, is used to simulate the strong ground motion characteristics and intensity distribution details caused by this earthquake in Beijing area. The simulation results of strong ground motion show that the areas with a peak velocity PGV>0.7 m·s-1 are concentrated in an 8~9 km wide strip along the east side of the fault, with a maximum value of 1 m·s-1; the intensity distribution shows that most of the area within 20 km around the fault exceeds Ⅷ. The results of this article can provide a reference for earthquake prevention and disaster reduction.