关键词: 水库地震, 断层活动性, 组构分析, 应力轴方位, 湖南

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