9706681 Chave Due to the recent turndown of analog submarine telephone cables by their commercial operators, an opportunity has arisen to make planetary scale measurements of the geoelectric field on unpowered cables around the globe. At present, such data are being collected on two Atlantic and nine Pacific cables by US and Japanese investigators; the record length is currently two to seven years. The proposed work is to use these data, together with geomagnetic variations measurements from standard observatories and dedicated magnetometers, to study the vertical and lateral variability of the deep (100-600 km) electrical structure of the sub-oceanic mantle beneath the Atlantic and Pacific with a resolution comparable to that from seismic normal modes. The oceanic structure will be compared to that beneath an Archaean craton in central Canada, and a petrophysical interpretation for the differences will be devised. ***
