Characteristics and distribution of the event deposits induced by the 2011 Tohoku-oki earthquake and tsunami offshore of Sanriku and Sendai, Japan

Ikehara, Ken; Usami, Kazuko; Irino, Tomohisa; Omura, Akiko; Jenkins, Robert G.; Ashi, Juichiro

doi:10.1016/j.sedgeo.2020.105791

Cited by 23 publications

(27 citation statements)

References 75 publications

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“…4 ). The same trend has been reported in the 2011 event deposits on the outer shelf of Sendai Bay 18 , 22 . As Cs can be strongly absorbed on mica-like clay minerals 37 – 39 , radioactive Cs might also absorb on the fine-grained clay minerals in the suspended shelf water.…”

Section: Discussionsupporting

confidence: 86%

“…3 C). However, the volume may be larger than estimated, because part of the resuspended mud was moved offshore to the outer shelf and further to the slope area following the turbidity currents 17 , 18 , 21 , 22 .…”

Section: Discussionmentioning

confidence: 93%

“…4 A,B) was formed after the FDNPP accident, while the lack of bioturbation in the redeposited mud indicates that the benthos activity (burrowing) did not lead to the subsurface occurrence of 134 Cs. Although large ground shaking by the 2011 earthquake might have contributed to surface sediment resuspension 22 , the following tsunami-induced shear velocity resulted in large-scale erosion and the resuspension of shelf mud. Since the release of radionuclides to the atmosphere from the FDNPP started on March 12, 2011 and peaked on March 15, 1 and 4 days after the earthquake and tsunami, respectively, the particles must have been suspended in the shelf water for at least several days.…”

Section: Discussionmentioning

confidence: 99%

“…Prior to the 2011 Tohoku-oki tsunami, the reports on the effect of tsunami on the marine surface sediments were very limited 13 – 16 . In contrast, several studies have reported the occurrence of coastal and offshore sediment remobilization due to the 2011 Tohoku-oki tsunami in large areas along the Pacific coast of Tohoku 17 – 22 . Nevertheless, the response of marine surface sediments to tsunami has not yet been fully understood, as it varies depending on the local environmental conditions and parameters such as bathymetry, coastline morphology and environment, grain size and composition of the surface sediment, size and direction of the tsunami wave.…”

Section: Introductionmentioning

confidence: 94%

“…Therefore, to better understand the offshore tsunami deposits and their formation processes and to quantify the impact of tsunami on the seafloor, comparative studies on surface sediments before and after tsunamis in as many locations as possible are necessary. Furthermore, some recent studies have indicated the possibility of tsunami-induced sediment transport from shelves to slopes 17 , 18 , 21 , 22 . Thus, it is important to consider the influence of shelf sediment remobilization by tsunamis on deep-sea sedimentation.…”

Section: Introductionmentioning

confidence: 99%

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The 2011 Tohoku-oki tsunami-induced sediment remobilization on the Sendai shelf, Japan, from a comparison of pre- and post-tsunami surface sediments

Ikehara

Irino

Saito

2021

Sci Rep

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Tsunamis are generally considered to disturb the seafloor, rework surface sediments, and change seafloor environments. However, the response of the seafloor to such extreme wave events has not been fully elucidated. Herein, we compare the surface sediments before and after the 2011 Tohoku-oki tsunami on the Sendai shelf and demonstrate that both sandy and muddy sediments were significantly reworked on the shelf. Muddy sediments (> 10 cm thick) were redeposited as graded mud with no or little bioturbation, characterizing the offshore muddy tsunami deposit, while well-sorted sand was found as the sandy tsunami deposit. This redeposited layer could also be retained in the shelf mud sequence. The results imply that the high friction velocity of the tsunami wave and its long-term effect on Sendai Bay might contribute to the large sediment reworking. Part of the resuspended mud moved offshore to the slope area as turbidity currents. Thus, the tsunami is an important mechanism not only for shelf sedimentation but also for deep-sea sedimentation along active plate margins. The detection of 134Cs derived from the Fukushima Daiichi Nuclear Power Plant accident in the redeposited mud indicates that the suspended shelf water state was maintained for some days after the tsunami.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The 2011 Tohoku-oki tsunami-induced sediment remobilization on the Sendai shelf, Japan, from a comparison of pre- and post-tsunami surface sediments

Ikehara

Irino

Saito

2021

Sci Rep

Self Cite

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Sediment Accumulation and Carbon Burial in Four Hadal Trench Systems

Oguri

Masqué

Zabel

et al. 2022

Preprint

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Hadal trenches are considered to act as depocenters for organic material, although pathways for the material transport and deposition rates are poorly constrained. Here we assess focusing, deposition and accumulation of material and organic carbon in four hadal trench systems underlying different surface ocean productivities; the eutrophic Atacama and Kuril-Kamchatka trenches, the mesotrophic Kermadec trench and the oligotrophic Mariana Trench. The study is based on the distributions of naturally occurring 210 Pb ex , 137 Cs and total organic carbon from recovered sediment cores and by applying previously quantified benthic mineralization rates. Periods of steady deposition and discreet mass-wasting deposits were identified from the profiles and the latter were associated with historic recorded seismic events in the respective regions. During periods without mass wasting, the estimated focusing factors along trench axes were elevated, suggesting more or less continuous downslope focusing of material toward the interior of the trenches. The estimated organic carbon deposition rates during these periods exhibited extensive site-specific variability, but were generally similar to values encountered at much shallower settings such as continental slopes and margins. Organic carbon deposition rates during periods of steady deposition were not mirrored by surface ocean productivity, but appeared confounded by local bathymetry. The inclusion of deposition mediated by mass-wasting events enhanced the sediment and organic carbon accumulations for the past ∼150 years by up to a factor of ∼4. Thus, due to intensified downslope material focusing and infrequent mass-wasting events, hadal trenches are important sites for deposition and sequestration of organic carbon in the deep sea.Plain Language Summary Hadal trenches (>6,000 m water depth) occupy ∼1% of the world's ocean floor yet are largely underexplored, but recent studies have shown that these environments are depocenters for organic material and microbial activity is intensified when compared to shallower abyssal plains. However, transport and accumulation of sediment material to these hadal trenches is poorly understood. This study investigates sedimentation and accumulation dynamics of organic carbon in trenches using results of radionuclide analysis (in sediment from the Atacama, Kuril-Kamchatka, Kermadec, and Mariana trenches). The analysis shows that trench sediments consist of discreet layers representing both periods of continuous deposition and sudden mass-wasting events often triggered by historic earthquakes. Down slope focusing of material, intensified the deposition along the trench axes. However, the deposition rates exhibited extensive site-specific variations that were partly related to mass-wasting events which greatly enhanced not only mass accumulation but also organic carbon accumulation at the trench axes. Our results illustrate that mass-wasting events play an important role on supplying organic carbon to hadal communities and suggest that hadal tr...

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Geochemistry and mineralogy of the sediments in the New Britain shelf-trench continuum, offshore Papua New Guinea: Insights into sediment provenance and burial in hadal trenches

Lin

Luo

Chen

et al. 2021

Deep Sea Research Part I: Oceanographic Research Papers

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Characteristics and distribution of the event deposits induced by the 2011 Tohoku-oki earthquake and tsunami offshore of Sanriku and Sendai, Japan

Cited by 23 publications

References 75 publications

The 2011 Tohoku-oki tsunami-induced sediment remobilization on the Sendai shelf, Japan, from a comparison of pre- and post-tsunami surface sediments

The 2011 Tohoku-oki tsunami-induced sediment remobilization on the Sendai shelf, Japan, from a comparison of pre- and post-tsunami surface sediments

Sediment Accumulation and Carbon Burial in Four Hadal Trench Systems

Geochemistry and mineralogy of the sediments in the New Britain shelf-trench continuum, offshore Papua New Guinea: Insights into sediment provenance and burial in hadal trenches

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