TY - JOUR
T1 - Deep-sea bottom-water environment change caused by sediment resuspension on the continental slope off Sanriku, Japan, before and after the 2011 Tohoku Earthquake
AU - Wakita, Masahide
AU - Watanabe, Shuichi
AU - Yoshino, Jun
AU - Oguri, Kazumasa
AU - Nomaki, Hidetaka
AU - Kawagucci, Shinsuke
AU - Ariyoshi, Keisuke
AU - Nagano, Akira
AU - Fujikura, Katsunori
N1 - Funding Information:
We acknowledge the help of the staff of the Mutsu Institute for Oceanography and the Research Institute for Global Change of JAMSTEC, and the captains and crews of the R/V Mirai , T/V Oshoro-Maru , T/V Bosei-Maru , R/V Shinsei-Maru , and R/V Hakuho-Maru for their kind cooperation in sample collection and hydrographic measurements during the 2012–2018 cruises. We are grateful to K. Sasaki, H. Kawakami, T. Kasaya, Y. Furushima, T. Totyofuku, S. Tsuchida, Y. Fujiwara, H. Suga, and H. Uchida (JAMSTEC); I. Sakamoto and Y. Yokoyama (Tokai University); S. Otosaka and H. Ogawa (University of Tokyo); M. Takada, K. Tsubata, and T. Ohmura (Tohoku Environmental Science Services Corporation); and Y. Tanaka (Hachinohe Institute of Technology) for valuable discussion and comments. Methane analysis was supported by K. Tanaka and the Deep301 laboratory. We also thank the marine technicians of Marine Works Japan onboard the R/V Mirai , T/V Bosei-Maru , R/V Shinsei-Maru , and R/V Hakuho-Maru. Finally, we also express our deep thanks to editor and two anonymous reviewers who provided us many useful comments.
Funding Information:
We acknowledge the help of the staff of the Mutsu Institute for Oceanography and the Research Institute for Global Change of JAMSTEC, and the captains and crews of the R/V Mirai, T/V Oshoro-Maru, T/V Bosei-Maru, R/V Shinsei-Maru, and R/V Hakuho-Maru for their kind cooperation in sample collection and hydrographic measurements during the 2012–2018 cruises. We are grateful to K. Sasaki, H. Kawakami, T. Kasaya, Y. Furushima, T. Totyofuku, S. Tsuchida, Y. Fujiwara, H. Suga, and H. Uchida (JAMSTEC); I. Sakamoto and Y. Yokoyama (Tokai University); S. Otosaka and H. Ogawa (University of Tokyo); M. Takada, K. Tsubata, and T. Ohmura (Tohoku Environmental Science Services Corporation); and Y. Tanaka (Hachinohe Institute of Technology) for valuable discussion and comments. Methane analysis was supported by K. Tanaka and the Deep301 laboratory. We also thank the marine technicians of Marine Works Japan onboard the R/V Mirai, T/V Bosei-Maru, R/V Shinsei-Maru, and R/V Hakuho-Maru. Finally, we also express our deep thanks to editor and two anonymous reviewers who provided us many useful comments.
Publisher Copyright:
© 2022, The Author(s).
PY - 2022/12
Y1 - 2022/12
N2 - Abstract: The 2011 off the Pacific coast of Tohoku Earthquake occurred off southern Sanriku, Japan, on March 11 and generated strong shaking and huge tsunami along the entire eastern coast of Tohoku. The mainshock and numerous large aftershocks caused mass-wasting sedimentation events on the continental shelf, slope, and trench bottom. To investigate the impacts of the 2011 Tohoku Earthquake on the deep-sea bottom-water environment off Sanriku, we conducted shipboard surveys up to ~ 2000 dbar during 2011–2018 and long-term monitoring of the seafloor on the continental slope using a deep-sea station (~ 1000 dbar) off Otsuchi Bay during 2012–2018. The high turbidity (maximum ~ 6%) was observed for the bottom water deeper than 500 dbar on the continental slope of the entire area off Sanriku during 2012–2018. This high turbidity was caused by sporadic sediment resuspension induced by frequent large aftershocks. Furthermore, dissolved oxygen concentrations in the bottom layer from 1000 to 1500 dbar dropped significantly by about 10% after the earthquake, while nutrients and dissolved inorganic carbon showed no significant changes but exhibited wide variations. The high turbidity was associated with the increase in the concentrations of phosphate, dissolved inorganic carbon, and methane, as well as the decrease in those of dissolved oxygen and nitrate. This suggests that remineralization of suspended organic matter resulting from the respiration and denitrification of microbial communities after the earthquake caused the chemical properties of the deep-sea bottom-water. The deep-sea bottom-water environment change was maintained by sporadic sediment resuspension due to continued large aftershocks and was likely caused by variations in dissolved inorganic carbon and phosphate. There are two peaks in the concentration and carbon isotope ratio of methane on the deeper slope from 1000 to 2000 dbar near the hypocenter, which were advected along isopycnal surfaces of 27.38σθ (1000 dbar) and 27.56σθ (1500 dbar). The source of the shallower peak of chemical input is considered to be the sediment resuspension from the shallow sediment on the continental slope induced by the mainshock and large aftershocks. Graphical abstract: [Figure not available: see fulltext.]
AB - Abstract: The 2011 off the Pacific coast of Tohoku Earthquake occurred off southern Sanriku, Japan, on March 11 and generated strong shaking and huge tsunami along the entire eastern coast of Tohoku. The mainshock and numerous large aftershocks caused mass-wasting sedimentation events on the continental shelf, slope, and trench bottom. To investigate the impacts of the 2011 Tohoku Earthquake on the deep-sea bottom-water environment off Sanriku, we conducted shipboard surveys up to ~ 2000 dbar during 2011–2018 and long-term monitoring of the seafloor on the continental slope using a deep-sea station (~ 1000 dbar) off Otsuchi Bay during 2012–2018. The high turbidity (maximum ~ 6%) was observed for the bottom water deeper than 500 dbar on the continental slope of the entire area off Sanriku during 2012–2018. This high turbidity was caused by sporadic sediment resuspension induced by frequent large aftershocks. Furthermore, dissolved oxygen concentrations in the bottom layer from 1000 to 1500 dbar dropped significantly by about 10% after the earthquake, while nutrients and dissolved inorganic carbon showed no significant changes but exhibited wide variations. The high turbidity was associated with the increase in the concentrations of phosphate, dissolved inorganic carbon, and methane, as well as the decrease in those of dissolved oxygen and nitrate. This suggests that remineralization of suspended organic matter resulting from the respiration and denitrification of microbial communities after the earthquake caused the chemical properties of the deep-sea bottom-water. The deep-sea bottom-water environment change was maintained by sporadic sediment resuspension due to continued large aftershocks and was likely caused by variations in dissolved inorganic carbon and phosphate. There are two peaks in the concentration and carbon isotope ratio of methane on the deeper slope from 1000 to 2000 dbar near the hypocenter, which were advected along isopycnal surfaces of 27.38σθ (1000 dbar) and 27.56σθ (1500 dbar). The source of the shallower peak of chemical input is considered to be the sediment resuspension from the shallow sediment on the continental slope induced by the mainshock and large aftershocks. Graphical abstract: [Figure not available: see fulltext.]
KW - Continental slope
KW - Deep-sea bottom-water environment
KW - Dissolved inorganic carbon
KW - Dissolved oxygen
KW - Methane
KW - Sediment resuspension
KW - The 2011 off the Pacific coast of Tohoku Earthquake
KW - Turbidity
U2 - 10.1186/s40645-022-00515-1
DO - 10.1186/s40645-022-00515-1
M3 - Journal article
AN - SCOPUS:85140627600
SN - 2197-4284
VL - 9
JO - Progress in Earth and Planetary Science
JF - Progress in Earth and Planetary Science
IS - 1
M1 - 56
ER -