Electromagnetic study of the Atlantic continental margin using a section of a transatlantic cable

Abstract

The induction of currents in an approximately 1200 km length of the TAT‐7 transatlantic telecommunications cable by geomagnetic field fluctuations is studied. Analyses of the induced voltage drop across the essentially geomagnetically east‐west oriented cable and of magnetic field data obtained at field sites at the cable head (Tuckerton, New Jersey) and in New Hampshire show a very high correlation over a wide frequency range between the induced currents in the cable and the east‐west magnetic field fluctuations. The observations do not correspond to the classical ocean‐coast effects discussed in the literature. The results of the analyses suggest that there are telluric currents flowing in an approximately north‐south direction off the east coast of the United States. The electrical current flow could be primarily confined in the ocean water or channeled in a conductivity structure within the earth's crust and upper mantle. If the latter situation exists, as may be likely because of the wide range of frequencies over which the effect is seen, then the region of the induced current flow could be related to the east coast magnetic anomaly (ECMA). In this case, these results would indicate that in addition to being a static magnetic anomaly, the ECMA is a structure with significant electrical characteristics such as higher conductivity.