Japan Geoscience Union Meeting 2014

Presentation information

Oral

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-P06_PG] Three year observations of ocean infragravity waves by broadband seismometers and pressure gauges of Japanese seafloor n

3-min talk in an oral session

*Yoko TONO1, Kiwamu NISHIDA2, Yoshio FUKAO1, Akiko TO1, Narumi TAKAHASHI1 (1.JAMSTEC, 2.ERI)

Keywords:Infragravity wave, Nankai Trough, DONET

Ocean infragravity (IG) waves are sea-surface gravity waves with periods of several minutes and wavelengths up to tens of kilometers. We used a slant-stack technique to detect IG waves from the three-year period records (2011-2013) of the vertical component broadband seismograms and pressure gauges of the seafloor network deployed in the Nankai Trough region (DONET). IG signals show good match in waveform between the seafloor displacement and pressure with propagation speeds consistent with the seafloor depths of 2000 m. The signal intensities are strongly azimuth-dependent. Except for the days with extreme weather, waves incoming from the SE direction (from the deep ocean to the coast across the Nankai Trough) are by far dominant. The incoming direction sharply splits into two, SSE and ESE. Waves from the deeper ocean in the SSE direction are more dominated in longer-period components than those from the shallower ocean in the ESE direction. Amplitudes of these waves clearly show a seasonal variation, high in winter and low in summer. The effect of typhoon is to generate IG waves incoming from the source direction and those incoming from the NE-ENE direction through the corridor between the coast and the Nankai trough. The latter is often stronger than the former.