Correcting for SPM effects in airborne EM

Kratzer, T, Macnae, J and Mutton, A 2013, 'Correcting for SPM effects in airborne EM', in 23rd International Geophysical Conference and Exhibition, Melbourne, Australia, 11-14 August 2013, pp. 1-4.

Document type: Conference Paper
Collection: Conference Papers

Title Correcting for SPM effects in airborne EM
Author(s) Kratzer, T
Macnae, J
Mutton, A
Year 2013
Conference name ASEG-PESA 2013
Conference location Melbourne, Australia
Conference dates 11-14 August 2013
Proceedings title 23rd International Geophysical Conference and Exhibition
Publisher CSIRO
Place of publication Australia
Start page 1
End page 4
Abstract Recent noise reductions in airborne electromagnetic (AEM) 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 powerlaw decays as additional basis functions in constrained least-squares fitting. Application of the method to airborne time-domain electromagnetic (TEM) surveys shows that the method allows correction of SPM and hence aids significantly in conductive target identification.
Subjects Electrical and Electromagnetic Methods in Geophysics
Keyword(s) airborne EM
magnetic viscosity
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