深海域で見られた地すべり性堆積物 : スローMTD

  • 鶴 哲郎
    独立行政法人石油天然ガス・金属鉱物資源機構
  • 溝部 晃
    独立行政法人石油天然ガス・金属鉱物資源機構
  • 田中 暁
    独立行政法人石油天然ガス・金属鉱物資源機構
  • 田中 誠
    独立行政法人石油天然ガス・金属鉱物資源機構
  • 佐藤 隆一
    独立行政法人石油天然ガス・金属鉱物資源機構

書誌事項

タイトル別名
  • Gravity induced deposits observed in a deep water : Slow MTD
  • 講演 深海域で見られた地すべり性堆積物 : スローMTD
  • コウエン シンカイイキ デ ミラレタ ジスベリセイ タイセキブツ : スロー MTD

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説明

<p>An extremely low velocity layer was detected in a deep water area, whose velocity was estimated to be 1500 m/s by velocity analysis of the seismic data. Its thickness is approximately 500 m in average and exceeds 700 m in maximum. Although obtained data are limited to reveal its origin, the layer was interpreted to be a mass transport deposit based on the observations: a distribution feature spreading toward the deep water, a chaotic-to-transparent reflection pattern, basal erosions of the underlying sediments and a pressure ridge developed at the tip region. However, mass transport deposit is normally characterized by high seismic velocity according to previous studies, whereas such a mass transport deposit with low velocity is seldom reported. From detailed seismic interpretation, active normal faults cutting the seafloor were recognized in overlying sediments. The faults appear also to cut the uppermost part of the mass transport deposit. Moreover, pore pressure gradient within the deposit was estimated to be from 12.0 to 14.4 MPa/km, being comparable with the fracture gradient from previous study. As a result, the presently-detected low velocity layer can be concluded most likely as a slow-moving earthflow type of mass transport deposit in deep water.</p>

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