David Annetts

The effect of topography on airborne electromagnetic response

Summary We modeled the step 2.5D airborne electromagnetic (AEM) response of a typical prospecting system over a number of layered-earth models, each of which, contained a t opographic feature modeling a hill on which the slope varied from 5E to 45E.We found that the AEM response due to the hill was dependant upon flight direction, with secondary field components in the flight direction being more adversely affected than vertical components. In addition, we found that topographic responses persisted to very-late times, and suggest that this may lead to inaccurate interpretations of data if those interpretations are based upon imaging, or n-layered earth inversion techniques. We conclude that it is better to interpret data flown off, rather than onto topographic highs..