GEOPHYSICAL EXPLORATION METHOD USING THE VERTICAL ELECTRIC COMPONENT OF A VLF FIELD AS A REFERENCE

• US 3,763,419 A
• Filed: 03/23/1971
• Issued: 10/02/1973
• Est. Priority Date: 03/06/1969
• Status: Expired due to Term

• Current Assignee: Anthony Rene Barringer
• Original Assignee: Anthony Rene Barringer
• Inventors: Barringer, Anthony Rene
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US05/127,225
• Time in Patent Office: 924 Days
• Field of Search: 324/6-8,3,4
• US Class Current: 324/334
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

A geophysical exploration method and apparatus utilizing VLF fields produced by distant transmitters as a source of primary filed. The vertical electric alternating field component of the primary field is used as a stabel reference against which variations in magnetic alternating field components caused by inhomogeneities in earth conductivity can be measured.

Claims

1. A method of sensing distortions in an electromagnetic field which penetrates the earth, said electromagnetic field being radiated by a distant source of electromagnetic energy, said electromagnetic field comprising a generally horizontal alternating magnetic field which is distorted when it intersects inhomogeneities in earth conductivity, and a substantially vertical alternating electric field component which is substantially unaffected by inhomogeneities in earth conductivity, said method comprising:

receiving along a predetermined path, a first reference signal having a fixed phase relationship to the phase of the vertical alternating electric field component, said first signal being substantially independent of all components of said electromagnetic field other than said vertical electric field component, and said first signal constituting a reference signal against which magnetic field variations may be compared, and recording the amplitude of said first signal as a function of time to preserve the phase and amplitude information contained therein, receiving a second signal having a fixed phase relationship to the phase of at least one directional component of said alternating magnetic field and recording said second signal contemporaneously with said first signal to preserve the relative phase and amplitude information contained therein, and comparing the amplitude and phase of said first and second signals.

2. A method as claimed in claim 1 including the additional steps of receiving and recording, along the said predetermined path, another directional component of said alternating magnetic field, said magnetic components being horizontal and being mutually orthogonal, and measuring the amplitudes of any portions of said alternating magnetic field components which are in phase quadrature to said vertical alternating electric field component.

3. A method as claimed in claim 2 including the additional step of obtaining the square root of the sum of the squares of the amplitudes of each of said quadrature magnetic field components.

4. A method as claimed in claim 2 including measuring the amplitudes of any portions of said magnetic field components which are in phase with said vertical alternating electric field component.

5. A method as claimed in claim 4 including the additional step of measuring a horizontal component of the alternating electric field that is in phase quadrature to said vertical alternating electric field component and is parallel to the direction of propagation of said electromagnetic field.

6. A method as claimed in claim 5 including the additional step of obtaining the ratio of the said measured quadrature horizontal alternating electric field to the vertical component of the alternating electric field.

7. A method as cLaimed in claim 1 including the additional step of removing from said second signal components which are in phase quadrature to a phasor having an angle of 45* with respect to the phase of said vertical alternating electric field component.