Anomalous directional behaviour of induction arrows above elongated conductive structures and its possible causes

Abstract

On some well documented field examples, it is found that, straddled between oppositely directed induction arrows which signify the existence of a conductive structure, a narrow belt exists over which real induction arrows align with the strike of the conductor. This distinctive behaviour either appears to signify a weak three-dimensional character of the elongated structure, marking gradients in the conductivity or current distribution along the length of the conductive body, or simply represents control of currents flowing in another conductor positioned at right angles to the mapped conductor. The lateral extent of this anomalous zone correlates well with the width of the conductive body. Incorporation of this feature in the interpretation of the half-width of the anomaly provides realistic constraints on the likely depth of the conductive body.