A comparison of magnetotelluric analysis methods based on data from a site in the Moreton Basin.

Abstract

A magnetotelluric (MT) system with sampling frequencies in decade steps from 1 kHz to .01 Hz was operated at a site in the Moreton Basin, near Peaks Crossing, Queensland. The data were analysed by both the conventional rotated impedance and the Spitz eigenvalue methods, then resistivity?depth profiles were calculated using a Molochnov/Bostick inversion technique. The magnitude of the resistivity information derived from the two methods was found to differ substantially, presumably due to the three-dimensional nature of some of the underlying geological structures. The finer structural features were similar between methods, though the depth of these features varied due to the differing apparent resistivities. The variation of the principle directions in the Spitz method was much smoother. Comparison between the resulting profiles and geological and geophysical information in the area showed reasonable agreement with expected geological structures.