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

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