1887
Volume 18 Number 1
  • E-ISSN: 1365-2478

Abstract

ABSTRACT

Conventional processes of extracting magnetotelluric signals from noisy records are reviewed: instrument noises and noises that are generated close to the detectors can be eliminated by the usual auto‐ and crosscorrelation processes. Identification of coherent noises, such as pulses due to field sources that are not uniform over at least 100 km in oil exploration or 1000 km in crustal studies, is much more tedious.

The 5 components of the magnetotelluric field have been recorded in many areas in France at different periods of the year, (a) in non‐uniform field sources in the vicinity of electric railways and of 50 cycle power lines, and (b) in areas of strong inhomogeneity at depth on the flanks of steep structures and near the sea shore.

Means for detecting non‐uniformity are reviewed. Measuring the vertical component of magnetic pulses is a good way of estimating field uniformity: if vertical/ horizontal <10%, the uniform field assumption is valid, and the classical restitution formulas can be used; if vertical/ horizontal > 10%, uniformity can not be assumed and there is some difficulty in deciding whether non‐uniformity is due to the field source or to anisotropy or inhomogeneities at depth. Several ways to solve this difficulty are described.

The reliability of calculation of actual resistivity at various depths is examined as a function of the precision of apparent resistivity measurements.

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2006-04-27
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References

  1. Benderitter, Y., 1963, Etude, mise au point et étalonnage ? appareils mobiles pour la prospection magnétotellurique: Thèse 3ème cycle, Fac. des Sciences, Paris .
    [Google Scholar]
  2. Benderitter, Y., Bolusset, R., Dupis, A., Moatti, E. AND van Pham , Ngoc, 1967, Prospecting for oil with magnetotelluric cross‐soundings, 29th E.A.E.G. Meeting, Stockholm .
    [Google Scholar]
  3. Benderitter, Y., 1968, Appareillage magnétotellurique de prospection pétrolière, Rev. Inst. Franc. Pétrole, 23, 608–618.
    [Google Scholar]
  4. Benioff, H., 1960, Observations of geomagnetic fluctuations in the period range 0.3 to 120 sec, J. of Geoph. Research, 65, 1413–1422.
    [Google Scholar]
  5. Berdichevsky, M. N. AND Brunelli, B. E., 1959, Theoretical premises of magnetotelluric profiling, Bull. Acad. Sc. USSR. Geophys. Ser., 1061–1069.
    [Google Scholar]
  6. Berdichevsky, M. N. AND Zavadskaya, T. N., 1966, Magnetotelluric profiling with real and imaginary parts of the impedance.Explor. Geoph., Vol. 47, trad, du Russe, Consultants Bureau, New York.
    [Google Scholar]
  7. Brunelli, B. E., Alekseev, A. M., Berdichevski, M. N. AND Burds, O. A., 1959, Observation of short period variations in earth's electromagnetic field, Bull. Acad. Sc. USSR. Geophys. Ser., 864–871.
    [Google Scholar]
  8. Cagniard, L., 1953, Basic theory of the magnetotelluric method of geophysical prospecting, Geophysics18, 605–635.
    [Google Scholar]
  9. Cagniard, L., 1956, Electricité tellurique, Handbuch der Physik, Springer Verlag Berlin, 407–469.
    [Google Scholar]
  10. Cagniard, L. AND Morat, P., 1967, Extension de la prospection magnétotellurique àľ exploration off‐shore, ľ Hydrocarbure, 14 Avenue de la Grande Armée, Paris , vol. 104, 10–12.
    [Google Scholar]
  11. Campbell, W. H., 1959, Studies of magnetic field micropulsations with periods of 5 to 30 sec, J. of Geoph. Research64, 1819–1826.
    [Google Scholar]
  12. Cantwell, T., 1960, Detection and analysis of low frequency magnetotelluric signals, Ph. D. Thesis, M.I.T., Cambridge , Mass .
  13. Duffus, H. J., Shand, J. A., Wright, C. S., Nasmyth, P. W. and Jacobs, J. A., 1959, Geographical variations in geomagnetic micropulsations, J. of Geoph. Research64, 581–584.
    [Google Scholar]
  14. Duffus, H. J., Shand, J. A. AND Wright, C. S., 1962, Short range spatial coherence of geomagnetic pulsations, Can. J. of Phys.40, 218–225.
    [Google Scholar]
  15. Dupouy, G., 1950, Perturbations du champ magnétique terrestre et des courants telluriques par les chemins de fer électrifiés, Ann. de Géophys.6, fasc. 1, 18–50.
    [Google Scholar]
  16. Duroux, J., 1967, Caractère de ľ onde électromagnétique de surface engendrée par un dipole magnétique, Geophys. Prospecting15, 564–583.
    [Google Scholar]
  17. Egorov, Y. G. AND Chernozemova, V. G., 1965, Results of magnetotelluric sounding in the area of the Lovorgo Geophysical Station, Bull. of the Acad. Sc. USSR. Geophys. Ser., 82–85.
    [Google Scholar]
  18. D'Erceville, J. AND Kunetz, G., 1962, The effect of a fault on the earth's natural electromagnetic field, Geophysics, 27, 651–665.
    [Google Scholar]
  19. Fonarev, G. A. AND Ivanov, V. I., 1966, Magnetic fields of marine telluric currents, Geomagn. and Aeronomy6, 402–405.
    [Google Scholar]
  20. Fournier, H., 1963, La spectrographie directionnelle magnétotellurique à Garchy (Nièvre), Ann. de Geoph.19, 138–148.
    [Google Scholar]
  21. Grenn, A. W.Jr. AND List, B. H., 1962, The use of a total field magnetometer in the magnetotelluric method of geophysical prospecting, Texas Instruments Rept. SA4–A62.
    [Google Scholar]
  22. Jain, S. AND Wilson, C. D. V., 1967, Magnetotelluric investigations in the Irish Sea and Southern Scotland, Geophys. Journal12, 165–179.
    [Google Scholar]
  23. Kolmakov, M. V. AND Vladimirov, N. P.1961, On the equivalence of magnetotelluric sounding curves, Bull. Acad. Sc. USSR. Geophysics Series, 349–354.
    [Google Scholar]
  24. Kovtun, A. A., 1961, The magnetotelluric investigation of structures in inhomogeneous layers. Bull. Acad. Sc. USSR. Geophys. Ser., 1663–1667.
    [Google Scholar]
  25. Lavergne, M. AND Lecardonnel, G., 1966, Perfectionnement aux magnétomètres à bobines, Brevet Français n° 1.530.443, 20 Mai 1968.
  26. Madden, T. AND Nelson, P., 1964, A defense of Cagniard's magnetotelluric method, M.I.T. Geophysics Laborat., Project NR‐371–401.
    [Google Scholar]
  27. Morrison, H. F., Wombwell, E. and Ward, S. H., 1968, Analysis of earth impedances using magnetotelluric fields, J. of Geoph. Research73, 2769–2778.
    [Google Scholar]
  28. Musé, L., 1964, Considérations sur les caractéristiques et les possibilités de la méthode magnétotellurique dans le cadre ? une prospection géophysique industrielle, 26th E.A.E.G. Meeting, Pau .
    [Google Scholar]
  29. Neves, A. S., 1957,The generalized magneto‐telluric method, Ph. D. Thesis, M.I.T., Cambridge , Mass .
  30. Niblett, E. R. AND Sayn‐Wittgenstein, C, 1960, Variation of electrical conductivity with depth by the magnetotelluric method, Geophysics25, 998–1008.
    [Google Scholar]
  31. O'Brien, D. P. and Morrison, H. F., 1967, Electromagnetic fields in an N‐layer anisotropic half‐space, Geophysics32, 668.
    [Google Scholar]
  32. Plouff, D., 1966, Magnetotelluric soundings in the South Western United States, Geophysics31, 1145–1152.
    [Google Scholar]
  33. Price, A. T.1962, The theory of magneto‐telluric methods when the source field is considered, J. of Geophys. Res.67, 1907–1918.
    [Google Scholar]
  34. Rankin, D., 1962, The magneto‐telluric effect on a dyke. Geophysics27, 666–675.
    [Google Scholar]
  35. Schneider, E., Thellier, E. AND Thellier, Mme O., 1948, Contribution géophysique àľétude du Trias ophitique pyrénéen, Ann. de Geophys.4, 15–32.
    [Google Scholar]
  36. Srivastava, S. P., Douglas, J. L. AND Ward, S. H.1963, The application of the magnetotelluric and telluric methods in Central Alberta, Geophysics28, 426–446.
    [Google Scholar]
  37. Srivastava, S. P., 1965, Method of interpretation of magnetotelluric data when the source field is considered, J. of Geophys. Res.70, 945–954.
    [Google Scholar]
  38. Tikhonov, A. N., 1950, Determination of the electrical characteristics of the deep strata of the earth's crust, Dokl. Akad. Nauk. USSR73, 295–301.
    [Google Scholar]
  39. Tikhonov, A. N. AND Shakhsuvarov, D. N., 1956, On the possibility of using the impedance of the natural electromagnetic field of the earth in exploration of the upper layers, Bull. Acad. Sc. USSR. Geophys. Ser., 410–418.
    [Google Scholar]
  40. Vladimirov, N. P. AND Nikiforava, N. N., 1959, On the spectrum of variations in the natural terrestrial field, Bull. Acad. Sc. USSR. Geophys. Ser.;1305–1307.
    [Google Scholar]
  41. Vladimirov, N. P. AND An, V. A., 1962, A method of processing magneto‐telluric oscillograms, Bull. of the Acad. Sc. USSR. Geophys. Ser., 1075–1078.
    [Google Scholar]
  42. Vladimirov, N. P. AND Kleimenova, N. G., 1962, On the structure of the earth's natural electromagnetic field in the frequency range of 0.5‐100 cps, Bull. of the Acad. Sc. USSR. Geophys. Ser., 852–855.
    [Google Scholar]
  43. Vladimirov, N. P. AND Krylov, S. M., 1964, Characteristic of microvariations of the natural electromagnetic field, Bull. of the Acad. Sc. USSR. Geophys. Ser., 528–534.
    [Google Scholar]
  44. Vozoff, K., Hasegawa, H. AND Ellis, R. M., 1963, Results and limitations of magnetotelluric surveys in simple geologic situations, Geophysics28, 778–792.
    [Google Scholar]
  45. Vozoff, K., Ellis, R. M. AND Burke, M. D., 1964, Telluric currents and their use in petroleum exploration, Bull. of the Amer. Assoc. of Petrol. Geol.48, 1890–1901.
    [Google Scholar]
  46. Waeselynck, M., 1967, Etude de structures anticlinales ou synclinales par la méthode magnéto‐tellurique, Bull. Centre Rech. Pau, SNPA, 1, 417–436.
    [Google Scholar]
  47. Wait, J. R., 1954, On the relation between telluric [currents and the earth's magnetic field, Geophysics19, 281–285.
    [Google Scholar]
  48. Wait, J. R., 1960, Propagation of electromagnetic pulses in a homogeneous conducting earth, Appl. Sc. Res., section B, 8, 213–253.
    [Google Scholar]
  49. Wait, J. R., 1961, Theory of magnetotelluric fields, Jour. of Research of Nat. Bur. Of StandardsD66, 509–541.
    [Google Scholar]
  50. Ward, S. H., 1959, AFMAG, Airborne and ground, Geophysics24, 761–787.
    [Google Scholar]
  51. Ward, S. H., O'Donnell, J., Rivera, R., Ware, G. H. AND Frazer, D. C, 1966, AFMAG, Applications and limitations, Geophysics31, 576–605.
    [Google Scholar]
  52. Weaver, J. T., 1963, The electromagnetic field within a discontinuous conductor with reference to geomagnetic micropulsations near a coast line, Can. Journ. of Physics41, 484–495.
    [Google Scholar]
  53. Weaver, J. T., 1963, A discussion of the fault and dike problems in magnetotelluric theory, Geophysics28, 487–490.
    [Google Scholar]
  54. Woznick, B. J., 1967, Programs for the Analysis of Magneto‐Telluric Data, Part I et II, Geoscience Incorporated, Rept RU‐67001.
  55. Yungul, S. H., 1961, Magnetotelluric sounding three‐layer interpretation curves, Geophysics26, 465–473.
    [Google Scholar]
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