金沙江下游白鹤滩水库蓄水前后地震活动特征  

Characteristics of seismicity before and after impoundment of Baihetan dam in the lower reaches of Jinsha River

作　　者：郭伟 赵翠萍[1] 左可桢 赵策 GUO Wei;ZHAO CuiPing;ZUO KeZhen;ZHAO Ce(Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China;Seismological Bureau of InnerMogolia Autonomous Region,Hohhot 010010,China;Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局地震预测研究所,北京100036 [2]内蒙古自治区地震局,呼和浩特010010 [3]中国地震局地球物理研究所,北京100081

出　　处：《地球物理学报》2022年第12期4659-4671,共13页Chinese Journal of Geophysics

基　　金：中国地震局地震预测研究所基本科研业务费专项(CEAIEF20220401);重点研发课题(2021YFC3000703)共同资助.

摘　　要：白鹤滩水电站坝高289 m,库容高达206.27亿m^(3),是世界上仅次于三峡水库的高山峡谷型高坝大库容水库,设计最高水位825 m.白鹤滩水库坝址位于川滇菱形块体东边界,库区范围内存在多条晚第四纪以来活动的大型构造断裂带——四开交际河断裂、则木河断裂和小江断裂等,区域构造背景十分复杂.2016年以来在库区布设了密集水库地震监测台网,以全过程监测白鹤滩水库蓄水前后的地震活动及其变化.大坝2021年4月6日下闸蓄水,坝前水位由658.44 m至2021年9月30日上升至目前的最高水位816.61 m,水位抬升了158.17 m.基于水库地震监测台网和三维速度模型的定位结果,我们发现随着水库蓄水,库区地震活动图像发生了变化,沿金沙江及黑水河支流库区微震活动显著增强,且与水位变化密切相关.截至2021年12月31日,记录到库区发生地震7401次,其中M_(L)3以上地震12次,最大为2021年12月21日发生在四川宁南骑骡沟的M_(L)3.9地震.库区地震月频次由蓄水前的不到80次,上升为500次以上,2021年10月达到1200次.蓄水后,地震呈现以巧家县葫芦口为中心,沿金沙江向大坝方向、沿黑水河支流向NW宁南方向、沿小江断裂北段和金沙江向东川方向的Y字形区域集中分布的特征.蓄水后震源深度优势分布在10 km以内,且最先活动的葫芦口附近地震深度较浅.库区的地震活动b值大于1.0.地震活动分析显示,随着白鹤滩蓄水,库区小江断裂带北段出现了微震活动,后期应加强研究.Baihetan Hydropower Station is the world's second largest alpine-gorge-type high-dam and large-capacity reservoir after the Three Gorges Reservoir.The height of the dam is 289 meters,the storage capacity is as high as 20.627 billion cubic meters,and the maximum designed water level is 825 meters.The dam is located on the eastern boundary of the Sichuan-Yunnan diamond-shaped block.There are several large-scale active tectonic fault zones since the late Quaternary in the reservoir area,such as the Sikai-Jiaojihe fault,the Zemuhe fault and the Xiaojiang fault,and the regional tectonic background is very complex.Since 2016,aiming to monitor the seismic activity and its changes before and after the impoundment of Baihetan reservoir during the whole process,a dense reservoir seismic monitoring network has been set up.The dam began to store water on April 6,2021,the water level in front of the dam rose from 658.44 m to 816.61 m on September 30,2021,with a total rising of 158.17 m.Based on the relocation results obtained by applying tomoDDMC method to observed data recorded by the seismic array that has been deployed around the reservoir area,we find that with the impoundment,the seismic activity in the reservoir area has been changed obviously,and the microseismic activity in the reservoir area along Jinsha River and Heishui River tributary has increased significantly,which is closely related to the change of water level.As of December 31,2021,7,401 earthquakes have been recorded in the reservoir area,including 12 earthquakes above M_(L)3,the largest being the M_(L)3.9 earthquake that occurred in Qiluogou Town,Ningnan County,Sichuan Province on December 21,2021.The monthly frequency of earthquakes in the reservoir area increased from less than 80 to more than 500,and reached 1200 in October 2021.After the impoundment,earthquakes cluster in a Y-shaped area that centered on Hulukou,Qiaojia County.That is towards the dam along the Jinsha River,to the NW Ningnan direction along the Heishui River tributaries,to the south alo

关 键 词：白鹤滩水库 水位 水库地震活动 B值 

分 类 号：P315[天文地球—地震学]