摘要
On the basis of in situe detection,the main purpose of this paper is to study the anomaly genesis of the frequency selection method.In situ detection is performed in a water-filled cave,and practical anomaly curves are obtained.Based on the Maxwell equations and the boundary conditions,magnetic vector potential of a low resistivity sphere or a horizontal cylinder in a homogeneous harmonious vertical magnetic field is solved.The analytic expressions of an induced electric field outside the abnormities are obtained.Parameters of the model are assumed,and anomaly profiles of the induced electric field are also obtained.Results between practical prospecting curves are compared with theoretical simulating curves,and similar characteristics are indicated.The anomaly genesis of the frequency selection method is induced in the natural electric field for a water-filled low resistivity abnormity.The induced natural electric field is one of the important factors causing anomalies.