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A comparison of electromagnetic exploration systems

K. G. McCracken, M. L. Oristaglio and G. W. Hohmann
A comparison of electromagnetic exploration systems
Geophysics (March 1986) 51 (3): 810-818


Electromagnetic (EM) exploration systems fall into three distinct classes, (1) frequency domain, (2) impulse response, and (3) step response, and have overall frequency responses that approximate f (super +1) , f (super 0) , and f (super -1) . To examine further these three classes, the transfer function of a frequency-domain system, and the step and impulse response functions of ideal time-domain EM systems (TEM), are derived in terms of a single set of target-specific parameters. The inductive time constants of practical exploration targets extend over three orders of magnitude, imposing severe constraints on practical exploration systems. Field data demonstrate that the impulse TEM response from a conductive half-space may show a 100-fold spatial variability at early times (< or = 1 ms) and then will decrease to a two-fold variability at late times (> or = 4 ms). This differential variability influences the ability of an EM system to detect an exploration target. For a half-space where the impulse response varies as t (super -k) , an inductive target of time constant tau exhibits the greatest contrast to the half-space at a delay time of ktau for an impulse-response system, and at (k - 1)tau for a step-response system.

ISSN: 0016-8033
EISSN: 1942-2156
Coden: GPYSA7
Serial Title: Geophysics
Serial Volume: 51
Serial Issue: 3
Title: A comparison of electromagnetic exploration systems
Affiliation: CSIRO, Div. Miner. Phys., North Ryde, NSW, Australia
Pages: 810-818
Published: 198603
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 38
Accession Number: 1986-053590
Categories: Applied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
S35°00'00" - S14°00'00", E113°00'00" - E129°00'00"
N43°00'00" - N79°00'00", W124°00'00" - W56°00'00"
Secondary Affiliation: Schlumberger-Doll Res., USA, United StatesUniv. Utah, Dep. Geol. and Geophys., USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 1986
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