澜沧江大朝山水库蓄水前的地震活动本底

Seismicity Background before the Water Storage of Dachaoshan, Lancang River, Reservoir

分析了大朝山水库蓄水前,水库区域历史中强、强地震背景与1992年来的地震活动格局,及蓄水前9年中库坝区天然地震活动的时、空、强分布,结果表明大朝山水库区为地震活动水平较低的区域,库坝附近30km以2、3级地震活动为主,库首方向距大坝40km左右的景谷与库尾方向距大坝50km的昌宁、凤庆一带为5级地震活动区,外围100km左右的耿马、澜沧、普洱等地区为6、7级强震活动区;库坝区的地震活动基本符合G-R关系式,b值为0·69,累积应变曲线呈稳定增长趋势,时间分布上出现活跃与平静交替的分布格局。

The history moderate-strong seismicity background in the Dachaoshan Reservoir area before the water storage of the reservoir, the earthquake distribution and the time-, space- and intensity-distribution of natural earthquakes from 1992 to the water storage were analyzed in this paper. The results show that the seismicity level was very low at the reservoir area. In the area 30 km around the dam mainly occurred M2. 0 - 3.9 earthquakes. The M5.0 -5.9 earthquake activities distributed in the areas including Jinggu, about 40 km from the head of the dam, Changning and Fengqing, about 50 km from the tail of the dam; and the M6. 0 - 7.9 earthquakes occurred in the areas of Gengma, Langcang and Puer, about 100 km from the dam. The seismic activity in the reservoir area basically agrees with the G-R relationship, and the b-value is 0. 69. The strain accumulation curve shows a stable increasing trend, and quiet and active periods distribute alternatively in time.