江宁台井下地电阻率变化初步分析

Preliminary Analysis of Resistivity Variation in Deep-well Observation at the Jiangning Seismic Station

江宁台附近地铁可能对地电阻率观测的干扰较大,通过提取江宁台井下地电阻率夜间数据来分析其变化并探讨机理。结果表明:①江宁台井下地电阻率具备一定地表浅层抑制干扰能力,主要干扰源为地铁;②夜间1~3时数据突跳与地铁不定期维护有关;③井下地电阻率观测NS(AB=1000m)和NS(AB=200m)2018年10月开始出现快速下降变化后,江宁台周围地震强度明显增强,认为该变化与S340公路金属护栏无关;④井下地电阻率长趋势下降变化与周围深井水位变化一致,反映了周围区域应力调整的变化;⑤井下地电阻率观测EW(AB=200m)在安徽无为ML 4.1地震前出现的“U”型变化与新建S340公路无关;⑥江宁台井下地电阻率共观测到5次“U”型变化,认为与地震有关的可能性较大。

The URRT can cause great impacts on the deep-well resistivity observation.In this paper we analyzed the resistivity variation and discuss the mechanism by extracting the night data of geo-electrical resistivity in Jiangning Seismic Station.The results show that:①the deep-well observation of Jiangning station has good inhibition to surface and shallow interference,and the main source of interference for deep-well observation is the URRT.②The sudden change of data from 01 to 03 at night is related to the irregular maintenance of the URRT.③The rapid decline of the deep-well geo-electrical resistivity observation NS(AB=1000m)and(AB=200m)in October 2018may not be related to the metal guardrail of S340 highway,and the earthquake intensity around Jiangning station is obviously enhanced.④The decrease of the long trend of the deep-well geo-electrical resistivity is consistent with the change of water level in the surrounding deep well,which reflects the change of regional stress adjustment.⑤The“U”change of the deep-well geo-electrical resistivity EW(AB=200m)before the Anhui Wuwei ML4.1 earthquake is not related to the newly built S340 highway.⑥There are 5“U”changes in the deep-well geo-electrical resistivity of Jiangning station,which we believe that it is very likely to be related to earthquakes.