The response of a three-dimensional magnetic and conductive body in shallow depth electromagnetic prospecting

The study of the abilities of an elm apparatus for shallow depth prospecting necessitates that we analyse the experimental data through theoretical modelling. A 3-D model for a magnetic and a conductivity contrast is presented here. Applied to the Slingram type SH3 case (intercoil spacing equal to 1.5 m and frequency to 8 kHz) it shows that this apparatus is roughly equivalent to the classical Wenner 1 m array and is more sensitive than magnetic prospection to susceptibility changes occurring in the soil above 6 0 cm depth. The 3-D model will also be very valuable for the conception of improvements in the apparatus.