Electrical Conductivity Structure of the Australian Continent

                 

Principal Investigator

F.E.M.(Ted) Lilley

Research School of Earth Sciences

Awide range of sets of electromagnetic induction data now exists 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 currents flow preferentially. In this project, a thin-sheet model is considered to interpret these data. A numerical method which inverts such data automatically has been developed, to derive a thin-sheet model for Australia.  

Co-Investigators

     

Liejun Wang

Research School of Earth Sciences

     
             

   

Projects

v63 - PC

           
                 

What are the results to date and the future of the work?

A conductivity model for Australia has been obtained by inverting electromagnetic induction data. The known conductivity anomalies are well imaged by the model and conductance values for the anomalies have been determined. In addition, the inversion program has been applied to interpret more detailed induction data from Queensland. The derived conductivity model gives a detailed three-dimensional picture of the Carpentaria anomaly.

In future work, the program will be applied to data recorded near the south- east Australian coastline, in order to obtain a more detailed two- dimensional picture of the conductivity structure in that part of the continent.

What computational techniques are used?

The inversion is carried out by minimising both a misfit function and a model roughness function. The misfit function is a least-squares misfit and the model roughness is the first derivative roughness.

The model changes at each step of the inversion represents a compromise between fitting the data and reducing the model roughness. A conjugate gradient relaxation method is used to solve the final equation.

Publications

L. J. Wang, F. E. M. Lilley and F. H. Chamalaun, The large-scale electrical conductivity structure of Australia from magnetometer arrays, Exploration Geophysics, 28, 1997, 150-155.

                 
Appendix A -