Telluric current
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A telluric current (sometimes referred to as Magnetotelluric) is a extremely low frequency electrical current that occurs naturally over large underground areas at or near the surface of the Earth. Magnetotelluric includes the magnetism component of the natural circuit.
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Description
Telluric currents are influenced by the conductivity in the interior of the Earth. Telluric currents are induced by changes in Earth's magnetic field, which are usually caused by interactions between the solar wind and the ionosphere. Telluric currents can be measured and, after being normalized, provide information about current direction and the conductance.
Both the telluric and magnetotelluric methods are used for exploring the structure beneath Earth's surface (such as in industrial prospecting). For mineral exploration the target is conductive ore bodies. Other uses include exploration of geothermal fields, petroleum reservoirs, fault zones, ground water, magma chambers, and plate tectonic boundaries.
Patents
The United States Patent office has a division classification for geophysical electrical measuring devices of the telluric type (including magneto-telluric types).
See also
Further reading
- Gideon, D. N., A. T. Hopper, and R. E. Thompson, "Earth current effects on buried pipelines : analysis of observations of telluric gradients and their effects". Battelle Memorial Institute and the American Gas Association. New York, 1970.
External links
- Scripps Institution of Oceanography Marine EM Laboratory (http://marineemlab.ucsd.edu).
- Stephen, Jimmy, S. G. Gokarn, C. Manoj, S. B. Singh, "Effects of galvanic distortions on magnetotelluric data: Interpretation and its correction using deep electrical data (http://www.ias.ac.in/epsci/mar2003/Esb1470.pdf)". National Geophysical Research Institute. (PDF)
- Gummow, R. A., "Telluric and Ocean Current Effects on Buried Pipeline and their Cathodic Protection Systems (http://www.prci.com/publications/L51909e.htm)". CORRENG Consulting Service, Inc. December 03, 2002.
- Sinha, M. C., et. al., "Applications of 3-Dimensional Electromagnetic Induction by Sources in the Ocean, ISO-3D (http://www.soes.soton.ac.uk/research/groups/EM/iso3d/documents/AnnualReport98/)". RTD Project, MAST III (Area C: Marine Technology). MAS3-CT97-0120