HR: 0800h
AN: T51B-1342    [Abstracts]
TI: Time variation of the electromagnetic field transfer function by using a wavelet transformation
AU: * Suto, N
EM: suto@eps.nagoya-u.ac.jp
AF: Graduate School of Environmental Studies, Nagoya University, E-137,Furo-cho,Chikusa-ku, Nagoya, 464-0814 Japan
AU: Harada, M
EM: mharada@restaff.chiba-u.jp
AF: Venture Business Laboratory, Chiba University, 1-33, Yayoi,Inage, Chiba, 263-8522 Japan
AU: Nagao, T
EM: nagao@scc.u-tokai.ac.jp
AF: Earthquake Prediction Research Center, Tokai University, 3-20-1, Orido, Shimizu, Shizuoka, 424-8610 Japan
AB: Crustal activities, such as large earthquakes and volcanic eruptions, may affect electromagnetism structure changes. The Magneto-Telluric method (MT method) is widely used for monitoring the electrical conductivity structure of the Earth. Generally, MT method uses Fourier transform as a spectrum analysis to determine the response function. However, concerning the Fourier transform, the existence of artificial noises sometimes gives a large influence on the analysis, theoretically. Therefore, we used Wavelet Transform instead of the conversional Fourier transform because of the advantage of time-frequency (scale) resolution. Furthermore, we applied the Inter-Transfer Function (ISTF) method to the calculation of the response function (Halada et al. 2004,Phys. Chem. Earth). We used the Morlet wavelet as a mother wavelet for the analysis, which is characterized by a sinusoidal function with a Gaussian window. In this study, we applied above mentioned technique for the data of Nakatatsu mine, Mount Iwate and Kakioka geomagnetic observatory from 1998 to 2002. We have calculated ISTF, apparent resistivity and phase every 3 months interval. At this moment, we can say that clear ISTF changes of 20 % occurred in year 2000 summer. The authors believe ISTF technique is quite useful tool to monitor the crustal activities.
DE: 3255 Spectral analysis (3205, 3280)
DE: 4425 Critical phenomena
DE: 7209 Earthquake dynamics (1242)
SC: Tectonophysics [T]
MN: Fall Meeting 2005