Abstract
The deep electromagnetic sounding (DES) technique is one of the few geophysical methods, along with seismology, gravity, heat flow, which may be use to probe the structure of the Earth's mantle directly. The interpretation of the DESs may provide electrical conductivity profiles down to the upper part of the lower mantle. The electrical conductivity is extremely sensitive to most of the thermodynamic processes we believe are acting in the Earth's mantle (temperature increases, partial melting, phase transition and to a lesser extent pressure). Therefore, in principle, results from DES along with laboratory measurements could be used to constrain models of these processes.
The DES technique is reviewed in the light of recent results obtained in a variety of domains: data acquisition and analysis, global induction modeling and data inversion and interpretation.
The mechanisms and the importance of surface distortions of the DES data are reviewed and techniques to model them are discussed. The recent results in terms of the conductivity distribution in the mantle from local and global DES are presented and a tentative synthesis is proposed.
The geodynamic interpretations of the deep conductivity structures are reviewed. The existence of mantle lateral heterogeneities in conductivity at all scales and depths for which electromagnetic data are available is now well documented. A comparison with global results from seismology is presented.
Similar content being viewed by others
References
Banks, R.: 1969, ‘Geomagnetic Variations and the Electrical Conductivity of the Upper Mantle’,Geophys. J. R. Astr. Soc. 17, 457–487.
Beamish, D., Hewson-Browne, R. C., Kendall, P. C., Malin, S. R. C. and Quinney, D. A.: 1983, ‘Induction in Arbitrarily Shaped Oceans - VI. Oceans of Variable Depth’,Geophys. J. R. Astr. Soc. 75, 387–398.
Berdichevski, M. N., Fainberg, B., Rotanova, N. M., Smirnov, J. B. and Vanayan, L. L.: 1976, ‘Deep Electromagnetic Investigations’,Ann. Geophys. 32, 143–155.
Bullard, E. C. and Parker, R. L.: 1970, Electromagnetic Induction in the Oceans, In E. C. Bullard and J. L. Worwel (eds),The Sea, Vol IV, Wiley, New York, pp. 695–730.
Campbell, W. H.: 1987, ‘The Upper Mantle Conductivity Analysis Method Using Observatory Records of the Geomagnetic Field’,PAGEOPH 125, 427–457.
Campbell, W. H. and Schiffmacher, E. R.: 1985, ‘Quiet Ionospheric Currents of the Southern Hemisphere Derived from Geomagnetic Records’,J. Geophys. Res. 90, 6475–6484.
Campbell, W. H. and Schiffmacher, E. R.: 1988, ‘Upper Mantle Electrical Conductivity for Seven Subcontinental Regions of the Earth’,J. Geomag. Geoelectr. 40, 1387–1406.
Cermak, V. and Lastovickova, M.: 1987, ‘Temperature Profiles in the Earth of Importance to Deep Electrical Conductivity Models’,PAGEOPH 125, 255–284.
Chapman, S.: 1919, ‘The Solar and Lunar Diurnal Variation of the Earth's Magnetism’,Phil. Trans. R. Soc. Lond. (A),218, 1–118.
Chapman, S. and Price, A.: 1930, ‘The Electric and Magnetic State of the Interior of the Earth as Inferred from Terrestrial Magnetic Variations’,Phil. Trans. R. Soc. Lond. (A),229, 427–460.
Chen, P. F. and Fung, P. C. W.: 1991, ‘Electromagnetic Response Function for the Period of 27 Day in the Chinese Region’,J. Geomag. Geoelectr. 43, 979–987.
Counil, J. L., Menvielle, M. and Le Mouel, J. L.: 1987, ‘Upper Mantle Lateral Heterogeneities and Magnetotelluric Daily Variation Data’,PAGEOPH 125, 1–22.
Dmitriev, V. I., Rotanova, N. M., Zakharova, O. K. and Fiskina, M. V.: 1987, ‘Models of Deep Electrical Conductivity Obtained from Data on Global Magnetic Variational Sounding’,PAGEOPH 125(2/3), 409–426.
Duhau, S. and Favetto, A.: 1990, ‘The Conductosphere Depth at Equatorial Latitudes as Determined from Geomagnetic Daily Variations’,PAGEOPH 134, 559–574.
Fainberg, E. B.: 1980, ‘Electromagnetic Induction in the World Ocean’,Geophys. Surv. 4, 157–172.
Fainberg, E. B. and Singer, B. Sh.: 1980, ‘Electromagnetic Induction in a Non-Uniform Spherical Model of the Earth’,Ann. Geophys. 36, 127–134.
Fainberg, E. B., Kuvshinov, A. V. and Singer, B. Sh.: 1991a, ‘Electromagnetic Induction in a Spherical Earth with Non-Uniform Oceans and Continents in Electric Contact with the Underlying Medium -I. Theory, method and example,Geophys. J. Int. 102, 273–281.
Fainberg, E. B., Kuvshinov, A. V. and Singer, B. Sh.: 1991b, ‘Electromagnetic Induction in a Spherical Earth with Non-Uniform Oceans and Continents in Electric Contact with the Underlying Medium -II. Bimodal Global Geomagnetic Sounding of the Lithosphere’,Geophys. J. Int. 102, 283–286.
Hagger, B. H. and R. W. Clayton: 1989, ‘Constraints on the Structure of Mantle Convection Using Seismic Observations, Flow Models and the Geoid, In W. R. Peltier,Mantle Convection, Gordon and Breach Science Publishers, pp. 6577#x2013;764.
Hibberd, F. H. and Davidson, R. E.: 1988, ‘Global Scale of the Day-to-Day Variability of Sq’,Geophys. J. 92, 315–321.
Hobbs, B. A.: 1987, Conductivity profiles from global data,PAGEOPH 125, 393–407.
Hobbs, B. A. and Dawes, G. J. K.: 1979, ‘Calculation of the Effect of the Oceans on the Geomagnetic Variations with an Application to the Sq Field During the IGY’,J. Geophys. 46, 273–289.
Honkura, Y.: 1978, ‘Electrical Conductivity Anomalies in the Earth’,Geophys. Surv. 3, 225–254.
Kharin, E. P. and Semenov, V. YU.: 1986, ‘The Curve of Deep Magnetovariation Sounding in the Pacific Ocean Obtained by Continuum Spectrum Method’,Annales Geophysicae 4B, 329–334.
Kuvshinov, A. V., Pankratov, O. V. and Singer, B. Sh.: 1990, ‘The Effect of the Oceans and Sedimentary Cover on Global Magnetovariational Field Distribution’,PAGEOPH 134, 533–540.
Lognonné, P. and Romanowicz, B.: 1990, ‘Modelling of Coupled Normal Modes of the Earth: The Spectral Method’,Geophys. J. Int. 102, 365–395.
Mackie, R. L., Bennett, B. T. and Madden, T. R.: 1988, ‘Long-Period Magnetotelluric Measurements Near the Central California coast: A Land-Locked View of the Conductivity Structure Under the Pacific Ocean’,Geophys. J. 95, 181–194.
Malin, S. R. C. and Gupta, J. C.: 1977, ‘The Sq Current System During the International Geophysical Year’,Geophys. J. R. Astr. Soc. 49, 515–529.
Menvielle, M., Rossignol, J. C. and Tarits, P.: 1982, ‘The Coast Effect in Terms of Deviated Electric Currents: A Numerical Study’,Phys. Earth Planet. Int. 28, 118–128.
Omura, K.: 1991, ‘Change of Electrical Conductivity of Olivine Associated with the Olivine-Spinel Transition’,Phys. Earth Planet. Int. 65, 292–307.
Parkinson, W. D. and Hutton, V. R. S.: 1989, ‘The Electrical Conductivity of the Earth’, in J. A. Jacobs (ed.),Geomagnetism, vol. 3, Academic Press, pp. 261–322.
Petersons, H. F. and Anderssen, R. S.: 1990, ‘On the Spherical Symmetry of the Electrical Conductivity of the Earth's Mantle’,J. Geomag. Geoelectr. 42, 1309–1324.
Phinney, R. A. and Burridge, R.: 1959, ‘Representation of the Elastic-Gravitational Excitation of a Spherical Earth Model by Generalized Spherical Harmonics’,Geophys. J. R. Astr. Soc. 34, 451–487.
Rikitake, T.: 1961, ‘Sq and Ocean’,J. Geophys. Res. 66, 3245–3254.
Rikitake, T.: 1966, ‘Electromagnetism and the Earth's Interior’, Elsevier, Amsterdam.
Ritz, M. and Robineau B.: 1986, ‘Crustal and Upper Mantle Electrical Conductivity Structures in West Africa: Geodynamic Implications’,Tectonophysics 124, 115–132.
Roberts, R. G.: 1983, ‘Electromagnetic Evidence for Lateral Inhomogeneities Within the Earth's Upper Mantle’,Phys. Earth Planet. Int. 33, 198–212.
Roberts, R. G.: 1984, ‘The Long-Period Electromagnetic Response of the Earth’,Geophys. J. R. Astr. Soc. 78, 547–572.
Roberts, R. G.: 1986a, ‘The Deep Electrical Structure of the Earth’,Geophys. J. R. Astr. Soc. 85, 583–600.
Roberts, R. G.: 1986b, ‘Global Electromagnetic Induction’,Surv. Geophys. 8, 339–374.
Schmucker, U.: 1987, ‘Substitute Conductors for Electromagnetic Response Estimates’,PAGEOPH 125, 341–367.
Schultz, A.: 1990, ‘On the Vertical Gradient and Associated Heterogeneity in Mantle Electrical Conductivity’,Phys. Earth Planet. Int. 64, 68–86.
Schultz, A. and Larsen, J. C.: 1987, ‘On the Electrical Conductivity of the Mid-Mantle: I. Calculation of Equivalent Scalar Magnetotelluric Response Functions’,Geophys. J. R. Astr. Soc. 88, 733–761.
Schultz, A. and Larsen, J.: 1990, ‘On the Electrical Conductivity of the Mid-Mantle: II. Delineation of Heterogeneity by Application of Extremal Inverse Solutions’,Geophys. J. Int. 101, 565–580.
Schultz, A., Booker, J. and Larsen, J.: 1987, ‘Lake Bottom Magnetotellurics’,J. Geophys. Res. 92, 10,639–10,649.
Schuster, A.: 1889, ‘The Diurnal Variation of Terrestrial Magnetism’,Phil. Trans. R. Soc. Lond. (A),180, 467–518.
Semenov, V. YU.: 1989, ‘Evaluation of Mantle Conductivity Beneath Northern Hemisphere's Continents’,Izvestiya Earth Physics 25, 221–226.
Shearer, P. M. and Masters, T. G.: 1992, ‘Global Mapping of Topography on the 660-km Discontinuity,Nature 355, 791–796.
Takeda, M.: 1985, ‘UT Variation of Internal Sq Current and the Oceanic Effect During 1980 March 1–18’,J. Geophys. J. R. Astr. Soc. 80, 649–659.
Takeda, M.: 1989, ‘Mantle Conductivity from the Geomagnetic Sq Field’,J. Geomag. Geoelec. 41, 643–646.
Takeda, M.: 1991, ‘Electric Currents in the Ocean Induced by the Geomagnetic Sq Field and Their Effect on the Estimation of Mantle Conductivity’,Geophys. J. Int. 104, 381–385.
Tanimoto, T.: 1990, ‘Long-Wavelength S-Wave Velocity Structure Throughout the Mantle’,Geophys. J. Int. 100, 327–336.
Tarits, P. and Wahr, J.: 1992, ‘Electrical Conductivity Heterogeneities in the Mantle: Correlation with Mantle Velocity Structure’,AGU, San Francisco,abstract.
Wahr, J., Tarits, P. and Lognonń, P.: 1992, ‘Lateral Variations in D″ Electrical Conductivity: Possible Effects on the Secular Variation of the Nagnetic Field’,AGU, San Francisco,abstract.
Winch, D. E.: 1989, ‘Induction in a Model Ocean’,Phys. Earth Planet. Int. 53, 328–336.
Zhang, T. S. and Schultz, A.: 1992, ‘A Three-Dimensional Perturbation Solution for the EM Induction Problem in a Spherical Earth - The Forward Problem’,Geophys. J. Int. 111, 319–334.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Tarits, P. Electromagnetic studies of global geodynamic processes. Surv Geophys 15, 209–238 (1994). https://doi.org/10.1007/BF00689860
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00689860