Japan Geoscience Union Meeting 2014

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Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG67_2AM2] Ocean Floor Geoscience

Fri. May 2, 2014 11:00 AM - 12:45 PM 418 (4F)

Convener:*Kyoko Okino(Ocean Research Institute, University of Tokyo), Keiichi Tadokoro(Research Center for Seismology, Volcanology and Earthquake and Volcano Research Center, Nagoya University), Osamu Ishizuka(Institute of Geoscience, Geological Survey of Japan/AIST), Tomohiro Toki(Faculty of Science, University of the Ryukyus), Narumi Takahashi(Earthquake and Tsunami Research Project for Disaster Prevention, Japan Agency for Marine-Earth Science and Technology), Chair:Tomohiro Toki(Faculty of Science, University of the Ryukyus), Kyoko Okino(Ocean Research Institute, University of Tokyo)

12:00 PM - 12:15 PM

[SCG67-P15_PG] Acoustic characterization of abyssal plain, northwestern Pacific region

3-min talk in an oral session

*Kyoko OKINO1, Chie HONSHO1, Shiki MACHIDA2, Mitsuhiro OIKAWA3, Kentaro NAKAMURA4 (1.AORI, The University of Tokyo, 2.School of Creative Science and Engineering, Waseda University, 3.Hydrographic and Oceanographic Department, Japan Coast Guard, 4.School of Engineering, The University of Tokyo)

Keywords:marine acoustics, muti-beam echo sounder, backscattering intensity, abyssal plain

The old seafloor covered by pelagic sediment has not attracted large scientific attention and remained untouched for many years, however, the recent studies on intra-plate volcanism as well as the increasing interest in deep-sea natural resources focus spotlight on the abyssal plains. We analyzed the multi-beam bathymetry, beam intensity, and side-scan images of abyssal plain in the northwestern Pacific, around the Minami-Torishima (Marcus) Island. The data were collected by Japan Coast Guard as part of Japanese EEZ survey and by R/V Yokosuka for decades. The beam intensity data from multi-beam echo sounder were processed to create a backscatter mosaic without geometric distortion. The mosaic shows a large variation of acoustic characteristics in whole study area. The high backscattering areas at the foot of large seamounts likely reflect the distribution of volcaniclastic sediments and debris. We can also recognize another type of high backscattering areas in flat seafloor, where neither remarkable seamounts nor knolls exist. The latter type partly corresponds to the area where the high concentration of rare-earth elements were reported and may suggest a thin cover of uppermost soft sediment layer. We try to integrate the backscattering mosaics and the statistic analysis of bathymetry and to establish a new method of acoustic characterization of abyssal plain. We also plan to compare our results with piston core samples as ground references and to discuss the sedimentation process and the relationship with intra-plate volcanism on old seafloor.