US 4,047,098 AGranted

Process and a device for prospecting the ocean bed by measuring electromagnetic fields

OwnerJean Durouxinventor

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Abstract

The present invention relates to a process and a device for prospecting the ocean bed by measuring electromagnetic fields. A loop 4 emitting electromagnetic rays is towed by its electricity supply cables 3. These cables are twisted and possess a sufficient cross section to reduce their electrical resistance. The loop per se has a low reactance owing to the low frequency which is used. The pick-ups for the components of the magnetic or electric fields, which make it possible to detect the variations in resistivity of the ground, are situated with the supply generator for the loop 4 on the boat 1. The present invention is intended for use in prospecting for mineral resources situated under water and, more generally, for all geological studies carried out on ground covered by water.

Claims13

Dependent claims

A process for prospecting the beds of rivers, lakes or the ocean by means of an electromagnetic emission and the measurement of at least one component of the field obtained at a specific distance above the area to be prospected, comprising the steps of

generating a controlled electromagnetic emission continuously and at a predetermined frequency less than 100 Hz from a location at the surface of the water, and
measuring the amplitude and phase of the selected component or components at the surface of the water at a location spaced a relatively great distance from the location of the electromagnetic emission, said component or components being either the transverse electric component Ey at the water surface or at least two components including the radial magnetic component Hx and either the vertical magnetic component Hz or the transverse electric component Ey, the steps of generating and measuring being carried out during a single dragging movement over the surface of the water while maintaining substantially the same distance between the generating and measuring locations.

Dependencies are inferred from the claim text.