Technical Papers - Airborne Electromagnetics

Using the Moments of a Thick Layer to Map Conductance and Conductivity from Airborne Electromagnetic Data

Richard S. Smith, Fugro Airborne Surveys, Ottawa, and Terry J. Lee, Canberra.

Abstract

The moments of the airborne electromagnetic impulse response have been derived for a thick horizontal layer. These moments can be written in an analytic form for the first- and second-order moments, both for the horizontal component and the vertical component. In the limiting case of a thin sheet, the horizontal component has first-, second- and third-order moments, while the vertical component has first- and second-order moments. On the other hand, the limiting case of a half space only has first-order moments for both components. The analytic expressions for the moments can be inverted analytically, so that the half space conductivity, thin-sheet conductance, and conductivity and thickness can be estimated. The images derived from the higher-order moments better identify a deeper conductor. This is consistent with the higher-order moments being more responsive to deeper material.

Published in Journal of Applied Geophysics, Vol. 49 (3) (2002) pp. 173-183
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