Integrated interpretation of SPECTREM geophysical data

Abstract

Electromagnetic attribute maps of SPECTREM AEM data are useful for geological interpretation, particularly where prior ground knowledge is limited. Single time-window maps require a baseline drift correction, which is accomplished by line-by-line modal filtering. Time-constant maps remove much of the effect of flight height variation on acquired data, without making any assumption about the geometry of conductive bodies. In addition, they map the changing behaviour of the electromagnetic decay curve, not just its amplitude at a particular sample time, across a survev area. Combining three electromagnetic maps in a ternary plot can be used to incorporate a large degree of information from the electromagnetic decay curve into a single image. An RGB (red-green-blue) representation is found to be an effective display. However, low signal amplitudes at late time preclude very deep information from being incorporated into such an image.