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中島 崇裕; 國友 孝洋; 長尾 大道*; 熊澤 峰夫; 茂田 直孝
Handbook of Geophysical Exploration; Seismic Exploration, Vol.40, p.177 - 191, 2010/03
地下の電磁気的状態をモニタリングするための人工ソースを用いた探査手法を開発し、電磁アクロスと名づけた。この手法では使用する周波数帯に関係なく応用ができる。東濃地域に2方向の接地ダイポールにより送信するシステムを設置し、500Hz以下の拡散場領域での探査が行えるようになった。試験観測として、950m離れた受信点で観測をし、精密なテンソル伝達関数を取得することができた。この試験観測を1か月以上続け、降雨に対応した変動も見られた。
長尾 大道*; 中島 崇裕; 熊澤 峰夫; 國友 孝洋
Handbook of Geophysical Exploration; Seismic Exploration, Vol.40, p.213 - 227, 2010/03
Development of a powerful staking technique is important in the active monitoring in order to enhance effectively the signal-to-noise ratio(SNR) by utilizing not only quiet nighttime data but also noisy daytime data. Here we propose a staking technique for data obtained by the Accurately Controlled Routinely Operated Signal System(ACROSS) with a reasonable method for noise level evaluation. An essential point is that the SNR would enhance by a data stacking in reciprocal proportion to the square root of the time period of observation. We show an application of this stacking method to real seismic and electromagnetic data and obtained at our observation test site of ACROSS.
松本 裕史*; 茂田 直孝; 熊澤 峰夫; 中島 崇裕
Handbook of Geophysical Exploration; Seismic Exploration, Vol.40, p.121 - 133, 2010/03
Precise and reliable method for complex dielectric permittivity measurement was developed using the data processing method of ACROSS(Accurately controlled Routinely Operated Signal System) and aids in electric circuit and electrode installation to reduce bias in measurement. By using the method, we succeeded to clarify that moist quartz grains and glass beads causes such strong dielectric dispersion that dielectlic permittivity increases in reciprocal proportion to frequency, and exceeds 1.0E5 at 1mHz. Loss angle was of the order of 1.0E-2 radian relatively independent to frequency, which suggests possibility that moist crust has significant dielectricity that can be detected by EM prospecting method in future.
羽佐田 葉子*; 熊澤 峰夫; 鶴我 佳代子*; 國友 孝洋; 笠原 順三*
Handbook of Geophysical Exploration; Seismic Exploration, Vol.40, p.381 - 395, 2010/03
We have developed a method to extract "events" localized in time domain from a transfer function in frequency domain, which is a basic analysis method of ACROSS(Accurately-Controlled Routinely-Operated Signal System). As the previous procedure has some difficulties in practical application, a revised one based on maximum likelihood estimation has been designed. We present the basic theory inclusive of the revision and the practical procedure for automatic travel time determination. The numerical test supports the validity of this method for analysis of transfer functions involving plural "events" in time domain.