Large-scale electrical conductivity structure of Australia from magnetometer arrays

Abstract

A range of sets of electromagnetic observational data (geomagnetic depth sounding and magnetotelluric sounding) now exist for the Australian continent. These data show regions of the continent where the conductivity structure is approximately one-dimensional on a gross scale, relative to zones, called 'conductivity anomalies', where induced electric current flows preferentially. Progress is being made in the development of a numerical method which inverts such observational data automatically, to give an image of the conductivity distribution of the whole continent, set in its surrounding seas. The thin-sheet algorithms developed by Weaver and Weidelt and colleagues are employed, and conductance values are found for grid units in a sheet representation of the continent which extends from the surface down to depth 10 km. The grid units are typically 100 km in horizontal dimension. The model is solved by numerical inverse methods. This paper presents results obtained from inverting data in the form of Parkinson or Induction arrows, at a single period, for sites spread widely across Australia. The major continental conductivity anomalies are given quantitative expression in the model resulting from the inversion.