Improving the accuracy of shallow depth determinations in AEM sounding

MacNae, J 2004, 'Improving the accuracy of shallow depth determinations in AEM sounding', Exploration Geophysics, vol. 35, no. 3, pp. 203-207.

Document type: Journal Article
Collection: Journal Articles

Title Improving the accuracy of shallow depth determinations in AEM sounding
Author(s) MacNae, J
Year 2004
Journal name Exploration Geophysics
Volume number 35
Issue number 3
Start page 203
End page 207
Total pages 5
Publisher Australian Society of Exploration Geophysicists
Abstract Conductivity-depth images (CDIs) are finding application in salinity, groundwater, and environmental mapping. Hydrological modelling demands are for a much higher vertical resolution than the 10+m accuracy that was adequate in CDIs used for mineral exploration. Contractors are increasingly confident of system waveform, geometry, and some provide corrections for factors such as pitch, roll, and yaw. This increased system accuracy is the trigger for efforts in increasing the accuracy of processing. The CDI process makes a number of approximations in order to increase the speed of processing. One of the most critical in program EMFlow is an assumption that the transmitter and receiver are entirely within the current system induced in the ground at all delay times. This assumption equates to all components of the secondary field decaying monotonically with time. For typical fixed-wing AEM geometries, this assumption is poor for the z component of the response, and in fact on a CDI, z component data may predict the top of a surficial conductor to be several metres in the air. Allowing for part of the induced currents to lie between the transmitter and receiver, when coupled with an Inductive Limit constraint, leads to an accurate prediction of surficial conductors to lie at or below surface.
Subject Electrical and Electromagnetic Methods in Geophysics
Keyword(s) Conductivity depth images
conductivity shallow
DOI - identifier 10.1071/EG04203
Copyright notice © ASEG 2004
ISSN 0812-3985
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