The Electromagnetic Method measures earth's response to electromagnetic signals transmitted by an induction coil. The induction coil produces magnetic field alternating at various frequency. The alternating magnetic field induces electric current in the material under the ground, which in turn produces secondary magnetic field. The electromagnetic sensor measures intensity of this magnetic field. Response to high-frequency signal comes from shallow part of the ground, while deeper part of the earth responds to low-frequency signal.
Based on this response, electric conductivity and magnetic susceptibility are calculated for each frequency.
Since these properties varies depending on the nature of the rock, water saturation, salinity and other parameters, the resultant maps are used for estimation of the nature of