Japan Geoscience Union Meeting 2015

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Symbol H (Human Geosciences) » H-DS Disaster geosciences

[H-DS26] Submarine landslides and their consequences

Tue. May 26, 2015 6:15 PM - 7:30 PM Convention Hall (2F)

Convener:*Yujin Kitamura(Department of Earth and Environmental Sciences, Graduate School of Science and Engineering, Kagoshima University), Makoto Otsubo(National Institute of Advanced Industrial Science and Technology (AIST), Institute of Earthquake and Volcano Geology)

6:15 PM - 7:30 PM

[HDS26-P01] Slope failure observed off the eastern coast of Amami-Oshima Island, Central Ryukyu Islands

*Takeshi MATSUMOTO1 (1.Faculty of Science, University of the Ryukyus)

Keywords:Amami-Oshima, Ryukyu Islands, Slope Failure

Amami-Oshima Island is located along the Ryukyu Arc around 28.5N. Unlike the islands south Tokunoshima Island, no active across-arc faults are identified on and around this island. However, a large-scale (about 600km2) slope failure towards the Ryukyu (Nanseishoto) Trench is identified according to the topographic map based on the 500m-gridded topographic data by Japan Coast Guard. Precise topography and shallow sub-surface structure were observed by 3.5kHz sub-bottom profiler (SBP) through the two cruises by the Training Ship NAGASAKI-MARU owned by Nagasaki University in 2013 and 2014. Since this area is characterised by a potential methane hydrate reservoir, the relationship between the potential hydrate and the slope failure is also to be discussed. The slope failure was surveyed by total 6 SBP lines with the distance of 30 nm. Another slope failure is also identified along the northern slope of the deep sea valley NE offing of Amami-Oshima. This failure was surveyed by 4 SBP lines with the distance of 15 nm. The former site was characterised by rough topography consisting of many mounds with 200-300m in relative height and 2-4km in radius, whereas the latter site by smaller-scale blocks.