电极是否稳定可靠是地电阻率观测系统的重要指标之一，主要通过测量电极的接地电阻大小来评价其状态。首先，分析现有测量方法，认为线路加电测量法更合理，提出考虑电缆线电阻的线路加电测量法；其次，采用该方法和接地电阻测试仪测量方法，测量江宁台多套地电观测系统电极的接地电阻，比较分析后者的结果误差；第三，讨论其接地电阻超出标准、同深度不同电极接地电阻差异及同井孔不同深度电极接地电阻差异，其原因可能与地下低电阻率区域及电极周围的地层湿度、介质的孔隙度有关，并分析了加电测量法存在的不足；最后，当接地电阻超标时，应该依据其变化幅度来判定电极是否稳定可靠。

Electrode stability is an important index of geo-electrical observation,and usually is evaluated by measuring its earth resistance. In this paper,we analyzed the existing measurement methods,and believed that the method of electrical measurement is more reasonable. An electrical measurement method considering cable resistance then is proposed. Taking Jiangning Station as an example,several methods were used to measure the earth resistance,and compared the result errors from different methods. We found that the electrical measurement method is more suitable for deep borehole observation. Furthermore,we discussed the grounding resistance out of standard and the earth resistance of electrodes at the same depth in different boreholes as well as at different depths in the same borehole,in which the big difference may be related to the formation humidity around the electrode and the porosity of the medium. The disadvantages of electrical measurement method are also analyzed in the paper. Finally,we suggested that when the earth resistance exceeds the standard,the stability of the electrode should be judged by its variation range.

P315

地震科技星火计划（XH19015YSX）、国家自然科学基金（A413740808）共同资助