Method and apparatus for transmitting electromagnetic signals into the earth at frequencies below 500 KHz from a capacitor emplaced on the surface of the earth or raised aloft in an aircraft

摘要

A method and apparatus comprising four co-planar metallic plates, two for transmission and two for reception, in which each pair of co-planer metallic plates of overall length L are disposed either in direct contact with the earth or are elevated a distance Z above the earth to form a capacitor comprising the metallic plates and the earth if Z=0 or if Z0, the metallic plates, the air space and the earth. A short voltage or current pulse is applied to this capacitor via a transformer in which the magnetic flux current is adjusted to provide a pulse of the desired frequency composition in the air-earth propagation medium. This results in a frequency controlled pulse of electromagnetic radiation into the targeted subterranean geology at frequencies 500 KHZ. In the preferred embodiment, the electromagnetic radiation that has propagated through the subsurface is iterated against a theoretical model for earth propagation of vertically traveling up-going and down-going waves to get a solution for the magnitude of the electrical properties as a function of the depth in the medium through which these waves have traveled. Electrical property vs depth profiles of the relative dielectric and the conductivity in addition to wave velocity and attenuation rate at depth in the subsurface are recovered by the iteration. For operation at capacitor altitude Z above the surface of the earth, the overall size of the capacitor, L, can be specified for use in the pulse spectrum below 500 khz.