| 講演要旨(和文) | | 地下浅部の比抵抗異常を検出することを目的として,AMラジオ放送波の水平と鉛直成分を受信し,両者の位相差を検出,表示する装置を製作した.この装置の性能を確かめるため,2006年3月に,薩摩川内市の川内川「シラス堤防」湛水試験場で,NHK鹿児島放送局のAMラジオ電波の位相測定を実施した.結果は,測定時,湿潤状態であった湛水池跡が,8〜10度の他より大きな位相差を示した.この位相値は,誘電率も考慮した2次元有限要素モデルから,深度1.5mにある約10Ω・mの低比抵抗層で説明できる. |
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| | 講演要旨(英文) | | The new system has been developed for prospecting of conductivity anomalies in shallow subsurface layers. This system with the simple electric circuits detects the phase difference between the horizontal and vertical magnetic components of AM radio waves in the frequency range of 500k to1600kHz, because phase parameters are relatively easy to measure. For an evaluation study of this system, a field survey was conducted on the test-field of Shirasu banks in Kagoshima Prefecture. The relatively large phase values were observed in the area where the surface layers are highly saturated with water. The 2D resistivity models indicate that these values are caused by the roughly 10 ohm-m layer at 1.5 m depth. |
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