Affiliation:
1. CGG Multi-Physics, Toronto L5N 5S2, Canada.(corresponding author).
2. Sander Geophysics, Ottawa K1V 1C1, Canada..
Abstract
The smoke-ring concept is a useful device for understanding how the electromagnetic fields induced in a 1D earth propagate and diffuse through a medium. Aside from facilitating a physical understanding of field propagation, the smoke-ring concept has been used to interpret behavior of vertical and radial magnetic fields at the surface and used to estimate depth of penetration for conductivity-depth transforms. Past studies have focused on the current distribution during the off-time. We have calculated the current in a half-space from a half-sine excitation (which provides a continuous induction). In comparison, the current pattern from a continuously excited waveform is more densely distributed in the near surface than the off-time current system, suggesting that measurements during a continuously excited on time are more sensitive to shallow targets. For airborne applications, in which the primary field coupling changes and is an important noise source, a primary field-stripping algorithm affects the current distribution but does not deleteriously affect near-surface sensitivity.
Publisher
Society of Exploration Geophysicists
Subject
Geochemistry and Petrology,Geophysics
Cited by
7 articles.
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