The application of Euler deconvolution to airborne EM data

Abstract

Euler's equation has traditionally not been used with electromagnetic fields because of a belief that it does not apply, because EM data obey Maxwell's wave equations rather than Laplace's equation. However if two approximations are employed then this is not the case. The approximations are ; 1) the effects of displacement currents are neglected; and 2) the contribution of the country rock is assumed to be small, due to its much lower conductivity than the target. In these situations then the wave equation reduces to Laplace?s equation. With frequencies <5000 Hz and an overburden:target conductivity ratio of <0.05 this approximation is valid. If Laplace's equation is valid then Euler's equation is also valid, and it may be used as a semi-automatic interpretation method in a similar manner to that with which it is used with magnetic and gravity data. It also allows for the downward continuation of EM data. The application of Euler deconvolution to airborne EM data is demonstrated both on data from synthetic models, and on real data over massive Ni-Cu sulphides associated with basic intrusive rocks.