Abstract: The research of regional seismic risk is fairly mature at present. Recently, a lot of papers concerning the simulation of the tectonic stress field of certain earthquake areas have been published. And by combining the obtained results with the other data, the seismic risk of the areas has been discussed and the risk areas of strong earthquake have been determined. In Yanhuai Basin where the Guanting reservoir is located, exist many active faults. The neotectonic movement in the basin has been very intense since Cenozoic era. The characteristics of historical earthquake activity and the crust-mantle structure of the basin indicate that strong earthquake is possible to occur in the basin in the future. Basing on the models and methods used in previous work, this paper studies the seismic hazard in Yanhuai Basin. Furthermore, by considering the possible impact of the presumed earthquake on the Guanting reservoir dam, the authors have assessed preliminarily the seismic safety of the dam. This paper focuses mainly on the possible impact of the expected earthquake on the dam. On the basis of filed work, together with the displacement data of active faults in Yanhuai basin, the modern tectonic stress field of the region has been simulated in this paper by using ANSYS finite element compute program. The result of simulation reveals that the orientation of the maximum principal compressive stress is N80°～85°E. Combining this result with the characteristics of some risk areas of strong earthquake in North China, we propose that the potential seismogenic fault in this basin should be the Fangjiachong-Yingmenkuang Fault, and according to previous studies the maximum magnitude of the potential earthquake is considered to be 7.25. Moreover, the intensity attenuation equation for the Yanhuai Basin and its vicinity is regressed, through which the intensity of presumed earthquake at the Guanting reservoir dam is determined to be 7 degree. The corresponding seismic vibration parameters of the presumed earthquake on the dam are estimated. The results show that the peak velocity is 165cm/s, the peak acceleration is 19 cm/s² and the minimum duration time of the shock is 20s. Taking the intensity factor singly into consideration, it seems that the presumed shock will have small effect on the dam, because the dam had been fortified to resist 9 degree earthquake intensity. However, the situation may change when some other factors such as the engineering conditions of the dam, the spatial relationship between the seismogenic fault and the dam, and the impact of historical strong earthquake on the dam are taken into account. The seismic risk of the Guanting reservoir dam may increase due to all these factors.

Key words: Guanting reservoir dam, active faults, stress field simulation, intensity attenuation equation, seismic safety

摘要： 官厅水库所在的延怀盆地有多条活动断层分布,新构造运动强烈.官厅水库大坝安全与否事关首都安全.为此,文中采用有限元方法结合断层位移资料,模拟了延怀盆地的现代构造应力场;参照模拟的结果,结合前人的研究成果,对设定地震的烈度进行了拟合,讨论了设定地震对大坝的影响.对官厅水库大坝的地震安全性进行了评价.结果表明:1)延怀盆地最大主压应力方向为N80°～85°E;2)可能的发震断层为方家冲-营门矿段断层;3)考虑大坝坝址的工程地质条件、发震断层与大坝的空间位置关系、历史大地震对大坝的影响等因素,则大坝的地震危险性将有所提高.

关键词: 官厅水库大坝, 活断层, 构造应力场模拟, 烈度衰减方程, 地震安全性