Electromagnetic geophysics and global tectonics.

Abstract

Lateral variations of electrical conductivity in the lithosphere and below it can be informative concerning both contemporary and ancient global tectonics. The methods of investigation include classical four-electrode resistivity depth probing, which is of special value in continental shields; magnetotellurics, long used on land and recently in the Pacific to show that in electrical terms the lithosphere is thicker, near an oceanic ridge, than had been expected; and magnetometer arrays, which are useful primarily in mapping highly conductive structures. Examples of the use of all three methods will be reviewed, with emphasis on the last. -Author