| 講演要旨(和文) | | 我々は，特に沿岸域における浅海底下探査に適用する海底電磁場測定装置(OBEM)の開発を行っている。2009年度には北海道北部の幌延町沿岸域にて予備実験的測定を実施した。2010年度では，小型3軸方位計の追加などを行い，幌延沿岸域での実地調査を遂行した。2010年度の測定結果による見掛比抵抗と位相データは全周波数帯域において2009年度よりも高品質であった。この結果は開発中のOBEMが沿岸域海底下の比抵抗構造調査に適用可能であることを示している。一方で，水深10m以浅の極浅海域では装置揺動ノイズにより特に中・低周波数帯域でデータ品質が低かった。より高品質なデータ取得のためには，測定時間の延長を含む改良が必要と考えられる。 |
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| | 講演要旨(英文) | | We have been developing ocean bottom electromagnetometers (OBEM) that can be used for performing shallow seafloor exploration, especially in the coastal area. A preliminary experiment in the coastal area of Horonobe, northern Hokkaido, was performed in FY 2009. In FY 2010, we improved our OBEM by adding an ultra-small tri-axial compass to it, and we conducted a field survey in the shallow sea of the Horonobe field. The apparent resistivity and phase obtained from the observed data are considerably higher quality than those obtained from the data of FY 2009, over the entire frequency range (10-3 to 125 Hz). The results indicate that our OBEM system can be used to conduct a practical field survey to estimate the sub-seafloor resistivity structure in coastal areas. However, the quality of the data acquired at a very-shallow sea bottom (shallower than 10 m) is still poor, especially in the middle and low frequency bands because of the presence of motion noises. Additional improvements, including longer data acquisition time, will be required to obtain data of better quality. |
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