
TY  - JOUR
A1  - Kratzer, Terence 
A1  - Macnae, James 
A1  - Mutton, Paul 
T1  - Correcting for SPM effects in airborne EM
JF  - ASEG Extended Abstracts
JO  - ASEG Extended Abstracts
Y1  - 2013
VL  - 2013
IS  - 1
SP  - 1
EP  - 4
KW  - 
UR  - https://doi.org/10.1071/ASEG2013AB050 
N2  - 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. 
ER  -

