The Research On Anomaly Genesis Of The Natural Electric Field Frequency Selection Method Based On Three-dimensional Electromagnetic Fields

The natural electric field frequency selection method evolves from early earth current method and audio magnetotelluric method, it have mainly carried out research by the domestic scholars,not reported abroad. And it has a low cost, convenient construction,fast detection, small topography and other characteristics, especially in the investigation of groundwater resources and exploration in the mine water have obtained the good application effect. Therefore, this method obtains more and more recognition and attention by everyone. Because of the source of natural electric field frequency method is not very clear, scholars pay more attention to the development of the instrument and practical application in the past, there is little literature above the method of theoretical research.Research and analyse the source of two-dimensional fields of natural electric field frequency method, it doesn't exactly correspond to the actual process due to simply consider a single direction of the electric field magnetic field.Therefore, it has very important practical significance for further analysis abnormal formation on the three-dimensional fields source of the abnormal formation.This paper mainly from a sphere in homogeneous half space to study the anomaly genesis of the frequency selection method. First of all, from two aspects of natural factors and human factors analyse the natural electric field method of frequency selective source problem. Based on the Maxwell equations and the boundary conditions, the analytic expressions of an induced electric field outside the conductive magnetic sphere are obtained for a sphere under harmonic magnetic field in homogeneous half space. According to Laplace equations and boundary conditions,the horizontal component of anomaly field on the surface is obtained for a conductive sphere under harmonic electric field in homogeneous half space. Parameters of models are assumed, profile curves of total electric field on the ground are calculated for a conductive sphere under three dimensional harmonic electromagnetic fields.Through analysing results of simulation of modeling, we can know that: there is not exist the contribution of alternating magnetic field in vertical direction.The discipline in two direction of the electric field component along with parameter changes are synchronized. Theoretical simulating curves are compared with the practical exploration curves, and similar characteristics are indicated when the sphere under horizontal harmonic magnetic fields and stray electric fields in homogeneous half space, it explains abnormal of natural electric field frequency method is mainlythe interaction results of horizontal alternating magnetic field and horizontal alternating electric field of human factors and natural factors.In conclusion, through natural electric frequency electric field method forward simulation model of sphere of natural electric field frequency method under the three-dimensional fields source, and analyse the results of the parameters of the model simulation, it benefits the further understanding of anomaly genesis of natural electric field frequency selection method,and provide certain guiding role in practical application in the future, it is beneficial for improving the accuracy of interpretation.