1887
Volume 20, Issue 1-2
  • ISSN: 0812-3985
  • E-ISSN: 1834-7533

Abstract

The Tasman Project of Seafloor Magnetotelluric Exploration (TPSME) took place between December 1983 and April 1984 (Filloux era/., 1985; Ferguson era/., 1985; Lilley , 1989). Seven magnetotelluric and two (additional) magnetometer sites spanned a range of tectonic features across the Tasman Sea. Initial analysis by Ferguson (1988) indicated large-scale three-dimensional induction effects to be present in the data. It was concluded that the most probable causes were the continental margin effect and changes in bathymetry.

In the present paper, a method is presented of modelling the salt water of the Tasman Sea and adjoining oceans as a thin sheet of variable lateral conductance, which overlies a series of uniform layers representing the solid Earth. The theory and a suitable computer algorithm were developed in a group led by J. T. Weaver at the University of Victoria, B.C., Canada. Many of the features present in the TPSME data are reproduced by this method, and with a greater understanding of induction processes in the ocean which is thus obtained, it is possible to remove three-dimensional effects from observed data. The TPSME data are then solely a measure of the response of the Earth directly beneath the observing sites, and one-dimensional modelling techniques may be used to determine the conductivity structures.

© 1989 ASEG
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1989-03-01
2026-01-19

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References

  1. Ferguson, I. J., Filloux, J. H., Lilley, F. E. M., Bindoff, N. L. and Mulhearn, P. J. (1985), ‘A seafloor magnetotelluric sounding in the Tasman Sea’, Geophys. Res. Lett, 12, 545-548.
  2. Ferguson, I. J. (1988), ‘The Tasman Project of Seafloor Magnetotelluric Exploration’, Ph.D. thesis, Australian National University, Canberra.
  3. Filloux, J. H., Lilley, F. E. M., Ferguson, I. J., Bindoff, N. L. and Mulhearn, P. J. (1985), ‘The Tasman Project of Seafloor Magnetotelluric Exploration’, Exploration Geophysics, 16, 221-224.
  4. Filloux, J. 1-1.(1987), ‘Instrumentation and experimental methods for oceanic studies’, in Jacobs, J.A. (ed.), Geomagnetism, Vol. 1, Academic Press, London, p. 143-246.
  5. Kellett, R. L, White, A., Ferguson, I. J. and Lilley, F. E. M. (1988), ‘Geomagnetic fluctuation anomalies across the Southeast Australian coast’, Exploration Geophysics, 19, 294-297.
  6. Lilley, F. E. M., Filloux, J. H., Ferguson, I. J., Bindoff, N. L. and Mulhearn, P. J. (1989), ‘The Tasman Project of Seafloor Magnetotelluric Exploration: experiment and observations’, Phys. Earth Planet. Inter., 53, 405-421.
  7. McKirdy, D. McA., Weaver, J. T. and Dawson, T. W. (1985), ‘Induction in a thin sheet of variable conductance at the surface of a stratified earth – II. Three-dimensional theory’, Geophys. J. R. Ast. Soc, 80, 177-194.
  8. Parkinson, W. D. (1959), ‘Direction of rapid geomagnetic fluctuations’, Geophys. J. R. Astr. Soc, 2, 1-14.
  9. Price, A. T. (1949), ‘The induction of electric currents in non-uniform thin sheets and shells’, Quart. Journ. mech. and Applied Math.,11, 283-310.
  10. Smith, R. S. and West, G. F. (1987), ‘Electromagnetic induction in an inhomogeneous conductive thin sheet’, Geophysics, 52, 1677-1688.
  11. White, A., Kellett, R. L. and Lilley, F. E. M. (1989), ‘The Australian Continental Slope Experiment along the Tasman Project profile’, Phys. Earth Planet. Inter, in press.
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  • Article Type: Research Article
Keyword(s): Electromagnetic induction; Tasman Sea; thin sheet modelling

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