EMAP Data Processing In the Wavenumber Domain

EMAP data processing is still in its infancy and many advances need to be made in understanding the effects that local near-surface features have on the observations, particularly on the wavenumber spectra ofgeological features. Current methodologies have several limitations which can result in less than optimum imaging of the conductivity structure below the EMAP profile. In particular, conventional EMAP filtering can remove details in the frequency-wavenumber domain which relate to the geological structure(s) of interest. In this paper, EMAP data, with 300 m electric field dipoles, from a 10 km LITHOPROBE line in south-eastern British Columbia will be presented. The data will be transformed from the frequency-space domain into the frequency-wavenumber domain, and the structure of the data examined to determme the most optimum filtering strateg) to adopt.. It will be illustrated that data specific strategies should bP employed rather than a general filtering rule. The importancr of the zero wavenumber response is stressed for deciding, to first order, th? maximum wavenumber to accept at a particular frequency.