Detection of deep-sea current associated with tsunami and possible biogenic acoustic signals — Several topics of multidisciplinary observation with JAMSTEC cabled observatory

On the occasion of “Off the Pacific Coast of Tohoku Earthquake” in 2011, water current changes in deep sea associated with tsunami were detected through the analysis at cabled observatories off Kushiro-Tokachi in Hokkaido and off Hatsushima Island in Sagami Bay, while it is usually difficult to detected them because they are usually much smaller than other oceanic events, such as tidal current, and some fluctuations after the earthquake in long-term gamma-ray observation data on deep seafloor in Sagami Bay were reported. In the “excavation” of possible biogenic and other episodic acoustic signals in a huge amount of legacy data accumulated for almost 20 years for the purpose of obtaining basic data for the development of species identification technologies for marine organisms. Peculiar low frequency signals were found which might possibly be biogenic, though more detailed research is necessary.