title: Hadal disturbance in the Japan Trench induced by the 2011 Tohoku-Oki earthquake.
abstract: In situ video observations and sediment core samplings were performed at two hadal sites in the Japan Trench on July, 2011, four months after the Tohoku-Oki earthquake. Video recordings documented dense nepheloid layers extending ~30-50 m above the sea bed. At the trench axis, benthic macrofauna was absent and dead organisms along with turbid downslope current were observed. The top 31 cm of sediment in the trench axis revealed three recent depositions events characterized by elevated (137)Cs levels and alternating sediment densities. At 4.9 km seaward from the trench axis, little deposition was observed but the surface sediment contained (134)Cs from the Fukushima Dai-ichi nuclear disaster. We argue that diatom blooms observed by remote sensing facilitated rapid deposition of (134)Cs to hadal environment and the aftershocks induced successive sediment disturbances and maintained dense nepheloid layers in the trench even four months after the mainshock.
authors.affiliation: Institute of Biogeosciences, Yokosuka Headquarters, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima, Yokosuka, Japan. ogurik@jamstec.go.jp
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Oguri
authors.forename: Kiichiro
authors.initials: K
authors.lastname: Kawamura
authors.forename: Arito
authors.initials: A
authors.lastname: Sakaguchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Toyofuku
authors.forename: Takafumi
authors.initials: T
authors.lastname: Kasaya
authors.forename: Masafumi
authors.initials: M
authors.lastname: Murayama
authors.forename: Katsunori
authors.initials: K
authors.lastname: Fujikura
authors.forename: Ronnie N
authors.initials: RN
authors.lastname: Glud
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kitazato
mesh_terms: D002588:Cesium Radioisotopes; D055866:Earthquakes; D019015:Geologic Sediments / Q000032:analysis*; D007564:Japan; D009792:Oceans and Seas; D011834:Radiation Monitoring; D011847:Radioactive Fallout / Q000032:analysis*; D018788:Radioactive Hazard Release; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D002588:Cesium Radioisotopes; D011847:Radioactive Fallout; D014875:Water Pollutants, Radioactive