Time variation of the electromagnetic transfer function of the earth estimated by using wavelet transform |
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| Authors: | Noriko SUTO Makoto HARADA Jun IZUTSU Toshiyasu NAGAO |
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| Institution: | *)Department of Earth and Environmental Sciences, Graduate School of Environmental Studies, Nagoya University, Aichi, Japan.;**)Earthquake Research Institute, University of Tokyo, Tokyo, Japan.;***)Venture Business Laboratory, Chiba University, Chiba, Japan.;****)Institute of Oceanic Research and Developments, Tokai University, Shizuoka, Japan. |
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| Abstract: | In order to accurately estimate the geomagnetic transfer functions in the area of the volcano Mt. Iwate (IWT), we applied the interstation transfer function (ISTF) method to the three-component geomagnetic field data observed at Mt. Iwate station (IWT), using the Kakioka Magnetic Observatory, JMA (KAK) as remote reference station. Instead of the conventional Fourier transform, in which temporary transient noises badly degrade the accuracy of long term properties, continuous wavelet transform has been used. The accuracy of the results was as high as that of robust estimations of transfer functions obtained by the Fourier transform method. This would provide us with possibilities for routinely monitoring the transfer functions, without sophisticated statistical procedures, to detect changes in the underground electrical conductivity structure. |
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| Keywords: | Interstation transfer function wavelet transform conductivity anomaly ULF geomagnetic field change earthquake-related electromagnetic phenomena |
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