Abstract:

Dongjiang Reservoir is located in southeastern part of Hunan Province, South China. The dam is 157m high. The capacity of the Reservoir is about 81.2 × 10⁸m³.Since August of 1986,it started to storage water,several thousands of induced earthquakes were recorded by the arrayof micro-seismic stations from November of 1987 to December of 1993, the maximum events of M_L＝3.0 occurred on 24 July,1989,and of M_L＝3.2, on 2 July,1990.Based on the research-es of regional geology,activity of the main fault zones,tectonic karstification by using the deter-mination and integrated analysis of time of fault activity, fabric characteristics, microstructures,structural joints,karstification and stress field, it could be suaggersted that there is no direct re-lationship between the occurrence of induced earthquake and the activity of the main fault zonesin the reservoir area. The distribution of induced earthquakes are confined in the area with kars-tificated strata and the complex weak zone with combination of multple structures. The authorsconsider that the percolation pressure can increase with the uprising level of storage water in thereservoir, and the induced earthquake will occur by the small fracturing or resliping along someweak plane or zone caused by the local stress adjustment. The induced earthquake activity willdeduce with the balance of local stress adjustment and the level of storage water in the reservoir.The maximum magnitude of induced earthquake in Dongjiang Reservoir will be below M_L＝4.0.

Key words: Reservoir earthquake, Faults activity, Fabric analysis, Stress axis orienta-tion, Hunan

摘要：

从区域地质、断裂活动性、构造岩溶等研究入手,应用多种断层活动年龄测定分析、岩组分析、显微构造和小构造分析、构造岩溶和应力场综合分析,提出,东江水库诱发地震与库区主要断裂带的活动性无直接联系,而是受岩溶地层分布和多种构造复合引起的复杂薄弱带的制约。当水库蓄水,水位上升,导致渗水,孔隙压力增大,致使薄弱带内部由于小规模破裂或薄弱面的重新滑动而进行的应力调整引起诱发地震。随着水库蓄水的稳定,内部应力逐渐调整趋于平衡,水库诱发地震活动性将逐渐趋于平静。

关键词: 水库地震, 断层活动性, 组构分析, 应力轴方位, 湖南