Abstract: The efficiency of Pb-Pbl₂ nonpolarised electrode in geoelectric field observation and its application in earthquake prediction are discussed in this paper. First, the observational data recorded in Lanzhou and Tianzhu stations by using Pb-Pbl₂ non-polarized electrodes are analysed according to the basic regularity of geoelectric field. The results show that such observational data mostly consist of physical values of geoelectric field, in which the fast change part is credible; the slow change part may include some small drift beside the real underground change. However, such drift, smaller than 1. 5 mV/km in 15 days, is much smaller than that of Pb electrodes. Second, PbPbl₂ non-polarized electrodes have been used for observation in Lanzhou and Tianzhu stations for 2~3 years, during that pe-riod two earthquakes, Yongdeng earthquake with M 5.8 and Tianzhu earthquake with M 5.4, occurred consequently. Through analysis it is found that distortion and abrupt changes in the pattern of daily geoelectric and geomagnetic field variations before Yong-deng earthquake appeared,which suggested that there were electro magnetic radiation dis-turbance around the seismic source; before Tianzhu M 5. 4 earthquake,there were obvious increased anomaly of natural electric potential in the observation direction, which is vertical to the fault, the reason is that Tianzhu station is just located along the seismic fault. All the results show that Pb-Pbl₂ non-polarized electrode is beneficial to develop observa-tion work and application study of geoelectric field up to a new stage.

Key words: Geoelectric field, Non- polarized electrode, Telluric anomaly