| 講演要旨(和文) | | 地震発生帯の海底下比抵抗構造を明らかにするために,東海沖の沈み込み帯におけるプレート間の地殻から深部のマントルにわたる構造を探査対象として,海底電磁気調査を実施した.自己浮上式海底電位磁力計(OBEM)および自己浮上式海底電位差計(OBE)を用いて計9地点で最長2ヶ月程度の海底電磁場データを取得した.MTデータ解析の結果,陸地から遠ざかるにつれて比抵抗が高くなる傾向があるが一部で一度比抵抗が下がるという南海トラフの特徴に似た比抵抗分布が確認された.また,周波数が低くなるにつれ見掛け比抵抗値は上がるが,単調増加ではなく比抵抗値がやや一定になる深度区間などが確認された.今後は得られたデータを紹介するとともに,MT法を用いた地殻構造解析について報告する. |
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| | 講演要旨(英文) | | Marine magnetotelluric(MT) soundings around the Enshu Basin, off the Tokai region, Japan, were carried out to clarify the crustal and mantle structures. Ocean bottom electro-magneto meter (OBEM) and Ocean bottom electro meter (OBE) were used in this survey to measure two marine electromagnetic field data sets over the subducting Philippine Sea plate, from January to February and from April to July in 2007. Both time series data of horizontal electric and magnetic fields were obtained at five sites, and only horizontal electric field data were obtained four sites. Apparent resistivity and impedance phase at some of each site were calculated from these observed data with selecting the time series data which were removed spike noises and a resistivity inclination below the seafloor at the region was estimated. It is meaning for marine MT surveys to interpret the estimated resistivity model with considering the relation of the characteristic in generation mechanism of earthquake. |
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