Abstract: Recently, remarkable rare gas anomalies have been observed in the water of Baolong and Tai-ping-zhuang wells in Beijing area, and Xialiao No.1 well in Xiaxian County, Shanxi Province. All these three wells are located in North China. According to the characteristics of rare gas anomalies in the three wells and the relationship between the anomalies and groundwater levels, theoretical analysis and experimental study have been carried out to gain an insight into the genesis of the anomalies. The results of experiments show that the volume of gases in the pores and fractures varies significantly with the evolution of groundwater dynamic condition. We find that the gas volume will expanse about 0.009 0% when the water level drops for 100mm. This may indicate that the anomalies of rare gases in these three wells are resulted from the expansion of gas volume and escape of gases due to the drop of groundwater level and the decrease of pore fluid pressures. It is proposed, therefore, that the rare gas anomalies discussed in this paper should not be earthquake precursor, but are anomalies caused by interference factors.

Key words: Rare gas anomaly, Pore pressure, North China

摘要： 介绍了近年来华北地区宝龙等3口井稀有气体的显著异常,并据其特征与井孔水位动态的关系,对稀有气体异常的成因进行了理论分析与实验研究.结果表明,水位下降100mm,岩层孔隙、裂隙中的气体体积膨胀0.009 0%(气体体积百分比,下同)左右.由于地下水位大幅度下降,岩层孔隙压力减小,积聚在岩层孔隙、裂隙中的气体体积膨胀溢出,导致井孔地下水中稀有气体含量出现异常变化.这些异常是干扰因素所致,不是地震异常.

关键词: 稀有气体异常, 岩层孔隙压力, 华北