中部マリアナトラフ拡大軸における火山活動位置についての考察 : 深海曳航式サイドスキャンソーナーと「しんかい6500」による高解像度観察の記録から

概要

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We collected high-resolution sidescan sonar imagery over the central part of active back-arc spreading basin, Mariana Trough, at 17° North ("Seg-17"). Spreading center is situated in the eastern side of the Mariana Trough, which divides the trough into approximately 3:2 in the west and east of the axis. Multi-scale observations, which are shipboard multi-beam bathymetric survey using R/V Yokosuka, the deep-towed side-scan sonar survey using Wadatsumi, and visual observation using submersible Shinkai6500, show that two predominant trends in geological features (fault, fissure, and volcanic ridge) are developed on the axial valley floor in either scale of observations. These two trends of linear features are almost parallel to each trend of "V-shaped ridge" developed along centerline of the axial valley floor. One trend is N15° W subparallel to the trend of the axial valley itself. Another trend is almost NS. There are no obvious differences in age between these two trending features. Volcanic activity is dominant in the western-half of the axial valley floor, which is indicated by the backscatter intensity pattern and by visual observations.
2012-03-30