Summary: | In this study, we identified the position of a methane plum in the Joetsu Basin by analyzing echo sounder images and GPS data. First, we observed the methane plume echo imagery, obtained using a quantitative echo sounder during a research cruise aboard JAMSTEC research vessel “Natsushima” in August 2013. Then we conducted two research cruises aboard the Nagasaki University training ship “Nagasaki-maru” during May 2014 and May 2015. During the 2014 cruise, we observed methane plume echo images at the position identified from the 2013 cruise data. During the 2015 cruise, we performed sea bottom core sampling at the same position using the methane plume echo imagery, and successfully obtained a methane hydrate core sample from the seafloor at a depth of approximately 560 m. 日本航海学会論文集, 134, pp.73-80; 2016 journal article
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