Transformation of electromagnetic anomalies brought about by a conducting host rock

Abstract

Small scale model experiments have been designed to investigate the electromagnetic anomaly produced by a buried conductor. These experiments show that a partially conducting host rock causes significant changes in the shape of the anomaly profiles as well as a general enhancement of the response. The diagnostic asymmetry of anomaly profiles obtained over inclined sheet models surrounded by a medium of vanishing conductivity was found to be progressively obliterated with increase in the conductivity of the host rock. As the conductivity increased, the sheet models tended to appear almost vertical irrespective of their dip and the coil system used. Both the variation in the apparent dip as well as the enhancement of response were found to be greater in the case of gently dipping sheets and were observed in varying degrees by all of the four different transmitter-receiver configurations used. The horizontal coplanar system recorded the maximum change and the vertical coplanar the least.