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A RECTANGULAR LOOP SOURCE OF CURRENT ON A TWO‐LAYERED EARTH *
Author(s) -
PODDAR M.
Publication year - 1982
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/j.1365-2478.1982.tb00416.x
Subject(s) - depth sounding , computation , amplitude , geology , displacement (psychology) , reciprocity (cultural anthropology) , geometry , magnetic field , physics , computational physics , geophysics , optics , mathematics , psychology , social psychology , oceanography , algorithm , psychotherapist , quantum mechanics
A bstract Using the concept of reciprocity and the known solution for the electric field of a vertical oscillating magnetic dipole source placed over a two‐layered halfspace, an integral expression for the vertical magnetic field produced by a horizontal rectangular loop, carrying an oscillating current and placed on the surface of the same halfspace, is deduced. This expression is such that it can be evaluated by a combination of straightforward numerical integration and digital linear filter techniques. Displacement currents everywhere in space are neglected. Fields both inside and outside the loop are presented as sounding curves. A little over a decade of frequencies (100–3000 Hz) appears to be the minimum requirement and two decades (100–10000 Hz) are sufficient for most situations. Parametric and geometric sounding curves both show good resolution of subsurface layering. Phase shows better resolution than amplitude. Similarly, resolution is higher when conductivity increases with depth than when it decreases. Besides being useful for the electromagnetic depth sounding for layered earth structures, such computations can be applied to determine normal corrections to Turam observations, whenever a rectangular loop of finite size is used as a transmitter.