关键词: 广西龙滩水库, 库水加卸载, 大地电磁测量, 视电阻率值

Abstract: Three times of magnetotelluric measurements were carried out during loading and unloading of the Longtan reservoir in Guangxi Zhuang Autonomous Region from 2009 to early 2010.The surveys were conducted at 4 sites with a frequency band 320Hz～1000s.The observational results show that the electricity of deep subsurface changed in different manners during the loading and unloading of the reservoir,depending on the specific structures and rock properties.At the 3 sites where the exposed rocks are of same lithology,the measured electric resistivity exhibited considerable variations at the band less than 1Hz.When the water level was the highest,the apparent resistivity was the lowest.As the water was declining,the apparent resistivity reached the maximum.And this value was the intermediate when the water level was the lowest.These measurements indicate that at different stages of loading and unloading of the reservoir,the rock properties,area of the reservoir and change of reservoir weight can pose a major influence on interconnection and seepage of underground water,causing variations of electricity of the subsurface at a certain depth.

Key words: Longtan reservoir of Guangxi, loading and unloading of reservoir, magnetotelluric measurement, apparent resistivity