HR: 0800h
AN: PP11B-0576 [Abstracts]
TI: Acoustical Surveys Of Methane Plumes By Using The Quantitative Echo Sounder In The Eastern Margin Of
The Sea of Japan
AU: * Aoyama, C
EM: aoyamac@dokken.co.jp
AF: Japan_fs Independent Institute Co.,Ltd., Ishii Bldg.7Fl.,3-1-10,Shinbashi,Minato-Ku, Tokyo, 105-0004
Japan
AU: Matsumoto, R
EM: ryo@eps.s.u-tokyo.ac.jp
AF: Dept. Earth and Planet Sci.,Tokyo Univ., 7-3-1,Hongo,Bunkyou-Ku,, Tokyo, 113-0033
Japan
AU: Okuda, Y
EM: okuda.gsj@aist.go.jp
AF: Inst.Geo-Resources and Env.,Nat.Inst.Adv.Ind.Sci.and Tech., 1-1-1,Higashi,Thukuba-city, Ibaraki,
305-8561
Japan
AU: Ishida, Y
EM: yasushi@eps.s.u-tokyo.ac.jp
AF: Dept. Earth and Planet Sci.,Tokyo Univ., 7-3-1,Hongo,Bunkyou-Ku,, Tokyo, 113-0033
Japan
AU: Hiruta, A
EM: hiruta@eps.s.u-tokyo.ac.jp
AF: Dept. Earth and Planet Sci.,Tokyo Univ., 7-3-1,Hongo,Bunkyou-Ku,, Tokyo, 113-0033
Japan
AU: Sunamura, M
EM: sunamura@eps.s.u-tokyo.ac.jp
AF: Dept. Earth and Planet Sci.,Tokyo Univ., 7-3-1,Hongo,Bunkyou-Ku,, Tokyo, 113-0033
Japan
AU: Numanami, H
EM: hnuma@kasei-gakuin.ac.jp
AF: Tokyo Kaseigakuin Univ., 2600,Aihara-machi,Machida-city, Tokyo, 194-0292
Japan
AU: Tomaru, H
EM: hitoshi@earth.rochester.edu
AF: Dept. Earth and Env.Sci.,Univ.Rochester, Rochester, Rochester, NY 14627
United States
AU: Snyder, G
EM: gsnyder@rice.edu
AF: Dept. Earth Sci. Rice Univ., 6100 Main Houston, Texas, Houston, TX 77005
United States
AU: Komatsubara, J
EM: jkomatsu@eps.s.u-tokyo.ac.jp
AF: Dept. Earth and Planet Sci.,Tokyo Univ., 7-3-1,Hongo,Bunkyou-Ku,, Tokyo, 113-0033
Japan
AU: Takeuchi, R
EM: lika@eps.s.u-tokyo.ac.jp
AF: Dept. Earth and Planet Sci.,Tokyo Univ., 7-3-1,Hongo,Bunkyou-Ku,, Tokyo, 113-0033
Japan
AU: Hiromatsu, M
EM: mhiromat@suruga-g.co.jp
AF: Nippon Kaiyo Corporation, 9-2,Sakae-cho,Kita-Ku, Tokyo, 114-0005_@
Japan
AU: Aoyama, D
EM: aoyamad@dokken.co.jp
AF: Japan_fs Independent Institute Co.,Ltd., Ishii Bldg.7Fl.,3-1-10,Shinbashi,Minato-Ku, Tokyo, 105-0004
Japan
AU: Koike, Y
EM: capkoike@s.kaiyodai.ac.jp
AF: Tokyo Univ. of Marine Sci. and Tech., 4-5-7,Kounan,Minato-Ku, Tokyo, 108-8477
Japan
AU: Takeda, S
EM: mbreeze@s.kaiyodai.ac.jp
AF: Tokyo Univ. of Marine Sci. and Tech., 4-5-7,Kounan,Minato-Ku, Tokyo, 108-8477
Japan
AU: Hayashi, T
AF: Tokyo Univ. of Marine Sci. and Tech., 4-5-7,Kounan,Minato-Ku, Tokyo, 108-8477
Japan
AU: Hamada, H
AF: Tokyo Univ. of Marine Sci. and Tech., 4-5-7,Kounan,Minato-Ku, Tokyo, 108-8477
Japan
AB:
The reseach and trainning/V, Umitaka-maru sailed to the methane seep area on a small ridge in the eastern margin of the Sea
of Japan on July to August 2004 to survey the ocean floor gas hydrate and related acoustic signatures of methane plumes by
using a quantitative echo sounder. Detailed bathymetric profiles have revealed a number of mounds, pockmarks and collapse
structures within 3km x 4km on the ridge at the water depth of 910m to 980m.
We mapped minutely methane plumes by using a quantitative echo sounder with positioning data from GPS. We also measured
averaged echo intensity from the methane plumes both in every 100m range and every one minute by the echo integrator.
We obtained the following results from the present echo-sounder survey.
1) We checked 36 plumes on echogram, ranging 100m to 200m in diameter and 600m to 700m in height, reaching up to 200m to 300m
below sea level.
2) We measured the averaged volume backscattering strength (SV) of each methane plume. The strongest SV, -45dB, of the plumes
was stronger than SV of fish school.
3) Averaged SV tend to show the highest values around the middle of plumes, whereas the SVs are relatively low at the bottom
and the top of plumes.
4) Some of the plumes were observed to show daily fluctuation in height and width.
5) We recovered several fist-sized chunks of methane hydrate by piston coring at the area where we observed methane plumes.
As a following up project, we are planning to measure SV of methane bubbles and methane hydrate floating in water columns
through an experimental studies in a large water tanks.
DE: 9320 Asia
DE: 4259 Ocean acoustics
DE: 1615 Biogeochemical processes (4805)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting