Abstract
Electromagnetometry at the sea floor has been developed over the last two decades taking advantage of the progress of positioning and acoustic technology in marine region. In spite of its risks and costs, electromagnetometry at the sea floor has significantly contributed to the study of conductivity anomalies through direct observations of electromagnetic variations at the sea floor. Some of the fruitful results of the ocean bottom observations around Japan as well as data processing of sea floor electromagnetic measurements are reviewed. Future problems in electromagnetometry at the sea floor are also discussed. In conclusion, the importance of establishing semipermanent electromagnetic observatories at the sea floor is emphasized.
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References
Asakawa E, Utada H and Yukutake T 1988 Application of Sompi spectral analysis to the estimation of the geomagnetic transfer function;J. Geomagn. Geoelectr. 40 447–463
Bindoff N L, Lilley F E M and Filloux J H 1988 A separation of ionospheric and oceanic tidal components in magnetic fluctuation data;J. Geomagn. Geoelectr. 40 1445–1467
Chave A D and Filloux J H 1984 Electromagnetic induction fields in the deep ocean off California: Oceanic and ionospheric sources;Geophys. J. R. Astron. Soc. 77 143–171
Cheesman S J, Edwards R N and Chave A D 1987 On the theory of sea-floor conductivity mapping using transient electromagnetic systems;Geophysics 52 204–217
Cox C 1980 Electromagnetic induction in the oceans and inferences on the constitution of the Earth;Geophys. Surv. 4 137–156
Edwards R N, Law L K, Wolfgram P A, Nobes D C, Bone M N, Trigss D F and Delaurier J M 1985 First results of the MOSES experiment: sea-sediment conductivity and thickness determination, Bute Inlet, British Columbia, by magnetometric offshore electrical sounding;Geophysics 50 153–160
EMSLAB Group 1988 The EMSLAB electromagnetic sounding experiment;Eos 69 98–99
Filloux J H 1967 An ocean bottom, D-component magnetometer;Geophysics 32 978–987
Filloux J H 1980a Observation of very low frequency electromagnetic signals in the ocean;J. Geomagn. Geoelectr. 32 (suppl. I) SI 1-SI 12
Filloux J H 1980b Magnetotelluric soundings over the northeast Pacific may reveal spatial dependence of depth and conductance of the asthenosphere;Earth Planet. Sci. Lett. 46 244–252
Hermance J F 1973 Processing of magnetotelluric data;Phys. Earth Planet. Inter. 7 349–364
Honkura Y 1974 Electrical conductivity anomalies beneath the Japan arc;J. Geomagn. Geoelectr. 26 147–171
Kaneko Y, Oshima S and Honkura Y 1988 Conductivity anomaly beneath Ryukyu arc; Programme and Abstracts, Society of Geomagnetism and Earth Planetary Space Sciences, Japan (in Japanese)
Kumuzawa M 1985 Physics of the earth and planet interiors; Lecture Note, Geophysical Institute, University of Tokyo
Ogawa Y, Yukutake T and Utada H 1986 Two-dimensional modelling of resistivity structure beneath the Tohoku district, northern Honshu of Japan by a finite element method;J. Geomagn. Geoelectr. 38 45–79
Rikitake T 1969 The undulation of an electrically conductive layer beneath the islands of Japan;Tectonophysics 7 257–264
Rikitake T and Honkura Y 1985Solid earth geomagnetism (Tokyo: Terra Sci. Pub. Co.) Vol 5, 384 pp
Sasai Y 1968 Spatial dependence of short-period geomagnetic fluctuations on Oshima Island (2);Bull. Earthq. Res. Inst. Univ. Tokyo 46 907–926
Segawa J, Kasuga T and Yukutake T 1981 Preliminary test on a three-component ocean bottom magnetometer;J. Geod. Soc. Jpn 27 293–251
Shiozaki I, Nogi Y, Yamaguchi S, Ohkubo A, Ichikita T, Yaskawa K, Fujiwara S and Sumitomo N 1988 Preliminary report on co-operative investigations of electrical resistivity structure beneath the Chugoku and Shikoku districts of Japan; Programme and Abstracts, Society of Geomagnetism and Earth, Planetary and Space Sciences, Japan (in Japanese)
Traits P and Honkura Y 1988 Sea effects on geomagnetic variations in the Japanese islands; Programme and Abstracts, Society of Geomagnetism and Earth, Planetary and Space Sciences, Japan (in Japanese)
Tatsumi Y 1989 Migration of fluid phases and genesis of basalt magmas in subduction zones;J. Geophys. Res. 94 4697–4707
Toh H, Fujimoto H and Segawa J 1988 A seafloor geomagnetic observation across the northern Izu-Bonin ridge; Programme and Abstracts, Society of Geomagnetism and Earth, Planetary and Space Sciences, Japan (in Japanese)
Utada H, Hamano Y and Yukutake T 1986 A two-dimensional conductivity model across central Japan;J. Geomagn. Geoelectr. 38 447–473
Utada H 1987A direct inversion method for two-dimensional modelling in the geomagnetic induction problem; PhD thesis, University of Tokyo
Yamano M 1986Heat flow studies of the circum-Pacific subduction zones; PhD thesis, University of Tokyo
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Segawa, J., Toh, H. Electromagnetometry at the sea floor. Proc. Indian Acad. Sci. (Earth Planet Sci.) 99, 639–656 (1990). https://doi.org/10.1007/BF02840319
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DOI: https://doi.org/10.1007/BF02840319