Abstract: At present, symmetric four-electrode configuration are used in the measurement of the geo-electric resistivity in most geo-electric stations in China. Usually, there exists phenomenon of annual variation of apparent resistivity, so it is difficult to identify earthquake precursors from these variations. One of the effective ways to solve this problem is using multi-separation array observation system. This paper introduced the experimental observation and preliminary data analysis in Shandan earthquake station by using the latest developed multi-separation array observation system-ZD8MI, which is satisfied for the demand of earthquake precursor observation. After a year's observation, the result shows that resistivity variation of shallow layer is lager than those of deep layers. Variation of apparent resistivity is relatively large in the case of small power polar distance (AB≤300 m), indicating that the shallow layer′s resistivity is greatly affected by the rain and human activity, while the deep layer is affected less. So the multi-separation array observation is important for the identification of earthquake precursors and the elimination of interferences.

Key words: Geo-electrical resistivity, Multi-separation array observation, Annual Variation