Inductive sounding of layered earth

Research aim. The research results in the development of a technology of continuous multi-frequency induction profiling measuring magnetic field components on long survey routes and detailed elaboration of sections by means of remote induction soundings. Research methodology. Theoretical and experimental studies of magnetic field components change patterns of harmonic vertical magnetic dipole over non-uniform layered earth. Mathematical simulation of harmonic vertical magnetic dipole magnetic field in non-uniform layered earth. Analysis of results. Information value of harmonic vertical magnetic dipole magnetic field components characteristics in low-frequency induction zone has been shown when studying non-uniform geoelectric sections together with the obtained results correspondence to the type of the non-uniform section when carrying out remote inductive sounding. 30 "Izvestiya vysshikh uchebnykh zavedenii. Gornyi zhurnal". No. 4. 2020 ISSN 0536-1028 Scope of results. for extended sections of route research (road and railway, oil and gas pipelines, power transmission lines, etc.) process sequence of vertical magnetic dipole magnetic field characteristics measurement has been determined to determine geoelectric properties of a layered section by means of continuous multi-frequency profiling and determination of homogeneous sections of medium structure with their detailing by discrete analysis by the method of remote inductive sounding.

Quasi-Static Solution for ELF/SLF near-Zone Field of a Vertical Magnetic Dipole near the Surface of a Lossy Half-Space

Dipole antennas over the boundary between two different media have been widely used in the fields of geophysics exploration, oceanography, and submerged communication. In this paper, an analytical method is proposed to analyse the near-zone field at the extremely low frequency (ELF)/super low frequency (SLF) range due to a vertical magnetic dipole (VMD). For the lack of feasible analytical techniques to derive the components exactly, two reasonable assumptions are introduced depending on the quasi-static definition and the equivalent infinitesimal theory. Final expressions of the electromagnetic field components are in terms of exponential functions. By comparisons with direct numerical solutions and exact results in a special case, the correctness and effectiveness of the proposed quasi-static approximation are demonstrated. Simulations show that the smallest validity limit always occurs for component H2z, and the value of k2ρ should be no greater than 0.6 in order to keep a good consistency.