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ASEG Extended Abstracts ASEG Extended Abstracts Society
ASEG Extended Abstracts
RESEARCH ARTICLE

Correcting for SPM effects in airborne EM

Terence Kratzer, James Macnae and Paul Mutton

ASEG Extended Abstracts 2013(1) 1 - 4
Published: 12 August 2013

Abstract

Recent noise reductions in AEM (airborne electromagnetic) systems have allowed detection of conductors at great depths, but systems now have also become sensitive to superparamagnetic (SPM) effects. We distinguish SPM effects in airborne electromagnetic survey data from the response of good conductors. In electromagnetic data processing, off-time data can be accurately represented as amplitudes of a set of basis functions that are comprised of decays that decrease exponentially as a function of time. The SPM impulse response can be approximated by a decay that is proportional to time to the inverse power, a time dependence associated with magnetic viscosity. We identify the presence of SPM effects, as distinct from the decay of good conductors, by using inverse power-law decays as additional basis functions in constrained least-squares fitting. Application of the method to airborne TEM (time-domain electromagnetic) surveys shows that the method allows correction of SPM and hence aids significantly in conductive target identification.

https://doi.org/10.1071/ASEG2013ab050

© ASEG 2013

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