The application of Zohdy?s method to AEM data

Abstract

Zohdy?s method for the modelling of DC-resistivity data has been adapted to the modelling of airborne electromagnetic (AEM) data. AEM responses are first transformed into apparent conductivity ? depth profiles, followed by an iterative adjustment of layer thicknesses and interval conductivities. The method is faster than layered-earth inversions, while offering the main advantages of Occam?s inversions. The start model, including the number of layers, is determined from the data, which optimises model flexibility without the need of parameter regularisation. While Zohdy?s method models abrupt vertical conductivity changes smoother than they are, results from synthetic and field data indicate that for some conductivity scenarios up to five distinct layers can be resolved from TEMPEST data. Modelled conductivity sections of TEMPEST data acquired across the Bull Creek prospect in Queensland clearly indicate the mineralisation beneath 30 m of conductive overburden.