METHOD AND APPARATUS UTILIZING A PAIR OF MAGNETIC FIELD DETECTORS AND AN ELECTRIC FIELD DETECTOR FOR DETERMINING THE ELECTRIC RESISTANCE OF THE SUBSOIL BY MEANS OF ELECTROMAGNETIC WAVES

摘要

1,239,953. Geophysical surveying. BUREAU DE RECHERCHES GEOLOGIQUES ET MINIERES. May 27, 1968 [June 6, 1967; Oct. 9, 1967 and Feb. 2, 1968], No. 25222/68. Heading G1N. The electrical resistance of the earth is determined by establishing a vertical electromagnetic field e.g. with a single turn coil and taking measurements, at a distance from the coil, of the vertical and radial components of the magnetic field and the transverse component of the electric field, and determining the resistance from mathematical formulae. Alternatively formulae (with a correction factor) may be used involving only the ratio of the magnetic field. Details of Apparatus. The magnetic field may be created by a single turn aluminium coil energized from a 300 watt variable frequency (D. C. to 30 kcs) power supply at 25 amps; a set of coils having the same resistance and diameters of 11-600m may be provided; the frequency may be varied in octave steps and corresponding bandpass filters used with the detectors.