Multiple-order moments of the transient electromagnetic response of a one-dimensional earth with finite conductance – the Gaussian variation applied to a field example
Date
2022-01-01
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Abstract
Formulae for the moments of the magnetic field response can be derived for simple models which have
conductivities that vary suddenly as a function of depth (thin and thick sheets) or not at all (half space). In
a companion paper we have derived expressions for the moments of a conductivity-depth profile that
varies smoothly, taking the form of a Gaussian function. In this paper we apply the Gaussian model to data
from Russell South, an area in the Athabasca Basin of Canada. The low signal-to-noise ratio in this area
means that estimating the overburden thickness is a challenging problem, so this dataset is a good
candidate for demonstrating the applicability of our approach. The estimated thicknesses can be
compared with drill information, also somewhat problematic as a reliable source of information. If we
constrain the Gaussian model to be similar to a thin sheet or a thick sheet at surface, we get estimates of
the overburden thickness which are much greater than what is inferred from drill information. However,
if the overburden is allowed to vary gradually and the depth and value of the maximum conductivity can
vary, then we find that the depth of the most conductive part of the overburden is realistic as it is
generally above the base of overburden as determined from drilling. Features of geological interest that
are not apparent on the original data can be identified on the derived images.
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Keywords
Airborne electromagnetics,, Canada, case histories, conductivity, interpretation, inversion, mineral exploration, multicomponent, uranium exploration, Athabasca basin
Citation
Richard S. Smith and Terry J. Lee, 2022, Multiple-order moments of the transient electromagnetic response of a one-dimensional earth with finite conductance – the Gaussian variation applied to a field example, Exploration Geophysics, DOI: 10.1080/08123985.2021.1925105