Magnetovariational and magnetotelluric studies of the Oulu anomaly on the Baltic Shield in Finland
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Published:
Feb 27, 1986
Keywords:
Baltic Shield,
Crustal conductivity structure,
Oulu conductivity anomaly,
Magnetotellurics,
Magnetovariational studies
Volumes
Vols. 1-18 (1924-1944), ISSN 0044-2801
Main Article Content
Abstract
The electrical conductivity structure of the Baltic Shield in Finland has been studied by magnetovariational (MV) and magnetotelluric (MT) work. First magnetometer arrays revealed the crustal Oulu conductivity anomaly which consists of a crustal conductive zone and a conductivity boundary. Since 1983 the magnetotelluric technique has been used to study the Oulu anomaly in more detail. The information obtained from the induction vectors of the MV and MT data are compared. 1 D and 2D models of the Oulu anomaly were constructed from MT data using induction vectors as additional information. In the centre of the research area the anomalous body (with a resistivity of 0.5 ohm m) lies below a depth of 4-7 km. Its width is about 25 km and its length is more than 100 km. To the south-west of this anomaly a low-resistive crustal layer exists at a depth of 14 km, whereas to the north-east no crustal layer was identified in the very resistive Karelidic realm.
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How to Cite
Korja, T., Zhang, P., & Pajunpaa, K. (1986). Magnetovariational and magnetotelluric studies of the Oulu anomaly on the Baltic Shield in Finland. Journal of Geophysics, 59(1), 32-41. Retrieved from https://journal.geophysicsjournal.com/JofG/article/view/229
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References
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Brewitt-Taylor, C.R., Weaver, T.J. (1976) On the finite difference solution of two dimensional induction problems. Geophys. J. R. Astron. Soc. 47:375-396
Fowler, D.F., Kotick, B.J., Elliott, R.D. (1967) Polarization analysis of natural and artifically induced geomagnetic micropulsations. J. Geophys. Res. 12:2871-2883
Gamble, T.D., Goubau, W.M., Clarke, J. (1979) Magnetotellurics with a remote magnetic reference. Geophysics 44:53-68
Hjelt, S.E., Kaikkonen, P., Pajunpaa, K., Korja, T., Heikka, J. (1985) Electromagnetic studies of the Baltic Shield in Finland. Ann. Geophys. (In press)
Jepsen, J.B., Pedersen, L.B. (1981) Evaluation of tensor AMT measurement system. Laboratory of Geophysics, Aarhus Univ. Geoskrifter 15
Johanssen, H.K. (1977) A man/computer interpretation system for resistivity soundings over a horizontally stratified Earth. Geophys. Prosp. 25:667-691
Jones, A.G. (1981) Geomagnetic induction studies in Scandinavia II. Geomagnetic depth sounding, induction vectors and coast-effect. J. Geophys. 50:23-36
Jones, A.G., Olafsdottir, B., Tiikkainen, J. (1983) Geomagnetic induction studies in Scandinavia III. Magnetotelluric observations. J. Geophys. 54:35-50
Jarvimaki, P., Puranen, M. (1979) Heat flow measurements in Finland. In: Cermak, V., Rybach, L. (Eds.) Terrestial heat flow in Europe. Springer Verlag, Berlin-Heidelberg-New York
Kozlovsky, Ye.A. (1984) The world's deepest well. Scientific American, December 1984:106-112
Kuppers, F., Post, H. (1981) A second generation Gough-Reitzel magnetometer. J. Geomagn. Geoelectr. 33:225-237
Kuppers, F., Untiedt, J., Baumjohann, W., Lange, K., Jones, A.G. (1979) A two-dimensional magnetometer array for ground-based observations of auroral zone electric currents during the International
Magnetospheric Study (IMS). J. Geophys. 46:429-450
Laajoki, K. (1984) The main tectonic features of the Baltic Shield in Finland. In: Hjelt, S.E. (Ed.) The development of the deep geoelectric model of the Baltic Shield, Part 2. Proceedings of the 1st project symposium, Oulu 15-18 November 1983, pp. 233-244. Dept. of Geophysics, Univ. of Oulu, Report No. 8.
Lange, K. (1979) Inductionseffekte in Nordskandinavien - untersucht am Beispiel zweier ostwarts fliessender polarer Elektrojets. Dipl. thesis, University of Munster, 160 pp.
Pajunpaa, K. (1984) Magnetometer array studies in Finland - determination of single station transfer functions. J. Geophys. 55:153-160
Pajunpaa, K., Heikka, J., Korja, T. (1983) Magnetometer array studies in Finland. J. Geomagn. Geoelectr. 35:543-553
Parasnis, D.S. (1975) Temperature phenomena and heat flow estimates in two Precambrian ore-bearing areas in North Sweden. Geophys. J. R. Astron. Soc. 43:531-554
Park, S.K. (1985) Distortion of magnetotelluric sounding curves by three dimensional structures. Geophysics 50:785-797
Pedersen, L.B., Svennekjar, M. (1984) Extremal bias coupling in magnetotellurics. Geophysics 49
Pedersen, L.B., Rasmussen, T., Roberts, R.G., Zhang, P. (1985) Remote reference magnetotellurics at Uppsala University. Paper presented at the XV Scandinavian Geophysicist Meeting (NOFTIG), Espoo, Finland, 15-17 January
Pernu, T. (1979) Studying of soil and bedrock structures with DC-resistivity measurements especially in Finnish conditions (in Finnish). Lis. thesis, Univ. of Oulu, 99 pp.
Roberts, R., Zhang, P., Pedersen, L.B. (1984) Remote reference magnetotelluric measurements (0.1-10 s) across the mylonite shear zone in southern Sweden. In: Hjelt, S.E. (Ed.) The development of the deep geoelectric model of the Baltic shield, Part 2. Proceedings of the 1st symposium of project no. 13 between the Academy of Finland and the Soviet Academy of Sciences, Oulu, 15-18 November 1983, pp. 328-339, Dept. of Geophysics, Univ. of Oulu, Report No. 8
Rokityansky, I.I. (1982) Geoelectromagnetic investigation of the Earth's crust and mantle. Springer Verlag, New York
Shankland, T.J., Ander, M.E. (1983) Electrical inductivity, temperatures and fluids in the lower crust. J. Geophys. Res. 88:9475-9484
Simonen, A. (1980) Precambrian in Finland. Geological Survey of Finland, Bull. 304