EM Induction in Elongated Conductors Normal to a Coastline with Application to Geomagnetic Measurements in Nigeria

Abstract

Magnetic induction responses of elongated pairs and single conductors with strikes perpendicular to a local coastline of a deep ocean are studied with the aid of laboratory model measurements. The dependence on period, the width of the conductor, and the distance from the end of the conductors are examined for traverses over the conductors. It is shown that for the model geometry studied, the ocean induction effects can be subtracted to yield the Parkinson induction arrows for the conductor alone. At sites between pairs of parallel conductors the quadrature arrows compared with the in-phase arrows show a very differing period dependence. These results have particular application to the interpretation of geomagnetic measurements at sites between major elongated conductive structures such as sediment filled grabens.