偶极接地线对地电阻率影响的数值模拟  

Numerical simulation for the influence of two-end grounded cables on georesistivity observation

作　　者：石富强[1] 邵辉成[1] 张国强[1] 方炜[1] 

机构地区：[1]陕西省地震局,中国西安710068

出　　处：《地震学报》2014年第6期1101-1112,1156,共12页Acta Seismologica Sinica

基　　金：陕西省地震局青年科研基金课题(201203);陕西省地震局启航与创新基金课题(201304);中国地震局监测预报司震情跟踪青年课题(2013020402);中国地震局地震科技星火计划项目(XH13023Y)共同资助

摘　　要：针对我国地震监测预报中地电阻率定点连续观测中存在的偶极接地线的干扰问题,本文将台站区域地层简化为3层均匀介质模型,将接地线等效为偶极接地的电阻体,建立了接地线干扰地电阻率观测的耦合物理模型.通过有限元分析软件ANSYS模拟分析不同电性断面情况下接地线对地电阻率观测的影响,同时分析这种干扰的产生机理,并结合实际观测中存在的干扰问题作了对比验证分析.结果表明:1接地线使得供电电极产生的地下对称性电场分布发生局部调整,从而影响地电阻率观测;2接地线对地电阻率观测的影响主要取决于线缆的位置及方位角的大小;3适当增大电极埋深可以减小其对地电阻率观测的影响;4电性结构的差异性决定干扰变化幅度的大小.本文结果对相关台站地电阻率观测异常分析落实及干扰源避让和观测系统改造具有参考意义.Two-end grounded cables often generate interference to continuous georesistivity observation at fixed sites for earthquake monitoring and prediction in China.By taking the grounded cables as two-end grounded resistors and sim-plifying the medium of geoelectric observation sites into horizontally inhomoge-neous three-layered medium,a coupled physical model is built up in this paper. Based on this model,influences of two-end grounded cables on georesistivity observation are simulated under different electric structures by using the finite element analysis software ANSYS.Furthermore,the effects of interference fac-tors,such as position,azimuth and buried depth of electrodes,on georesistivity observation are analyzed.And the interference mechanisms are also discussed. Besides,some existing interferences are also presented to give out a comparative study.The results showed that the first,the grounded cables can cause local adjustment of the symmetric underground electric field distribution generated by the current electrode,affecting normal georesistivity observation;the second, the effects of grounded cables on georesistivity observation,mainly depend on position of cables and their azimuth;the third,the effects tend to be reduced obviously with buried depth of electrodes increasing;and the forth,the differ-ence of the electric structures determine the magnitude of interference.The sim-ulation results are of significance as a reference to analyzing the similar resistivi-ty anomalies,choosing the evaded distance of the interference source and the re-form of the observing system.

关 键 词：地电阻率 偶极接地线 水平3层介质 干扰 数值模拟 

分 类 号：P315.722[天文地球—地震学]