Unusual BSRs and methane activity off Shimokita Peninsula in the western North Pacific

Kotani, Ryosuke; Matsumoto, Ryo; Ishida, Yukisato; Hiruta, Akihiro; Machiyama, Hideaki

doi:10.4096/jssj.64.117

Cited by 3 publications

(1 citation statement)

References 2 publications

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“…Bottom‐simulating reflectors and high‐amplitude anomalies can be observed in the seismic profiles (Taira et al, 2005), suggesting the presence of gas hydrate underlain by free gas. High methane fluxes are expected in the surface sediment from a shallow sulfate–methane interface (Kotani, Matsumoto, Ishida, Hiruta, & Machiyama, 2007). The relationship between methane hydrate and landslides has also been discussed for the area off Hidaka, in the northern part of the study area (Noda, TuZino, Joshima, & Goto, 2013).…”

Section: Geological Settingmentioning

confidence: 99%

Change in slide direction of submarine landslides in the Pliocene‐Quaternary deposits near the Shimokita Peninsula, northeast Japan, using 3D seismic data

2020

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Submarine landslides constitute a major mass transport process from shallow-to deep-sea and may have catastrophic impacts on both offshore infrastructure and coastal areas. Previous studies on submarine landslides have focused on triggering mechanisms and precondition perspectives, targeting limited numbers of short-term landslide events. Consequently, few studies have addressed long-term changes in landslide characteristics, including volume, direction, and timing. The areas studied herein are located on the continental slope facing the Japan Trench off the Shimokita Peninsula, northeast Japan, where a number of large-scale translational-type submarine landslide and accompanying unique dike structures have been identified in Pliocene to Recent deposits via 3D seismic data analysis. Here we developed a procedure for recognizing landslide deposits in 3D seismic data from the survey area, then investigated the 3D deposit distributions in detail. Because translational landslides preserve original structures, they can be used to estimate landslide volume. Parallel dike swarm features, which are interpreted as dewatering paths formed soon after landslide events, enable estimation of slide direction in time-slice images. Such analysis also allows differentiation of landslide deposits from background sediments and estimation of landslide volume. Landslides exceeding 50 km 3 in volume have occurred numerous times in the past 6 my. Landslides directions are observed from southwest to northeast over this entire period, whereas slides trending northwest to southeast started at 2 Ma. Although the landslide sizes vary greatly, the average landslide volumes are roughly constant throughout Pliocene and Quaternary time. Such shifts in long-term trends suggest a change in tectonics in the landslide source region. These unique long-term records (over 6 my) are enabled by the specific conditions in the study region, which include translational landslides, parallel dike swarms, and monotonous lithology.

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Section: Geological Settingmentioning

confidence: 99%

Change in slide direction of submarine landslides in the Pliocene‐Quaternary deposits near the Shimokita Peninsula, northeast Japan, using 3D seismic data

2020

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Possible Ground Instability Factor Implied by Slumping and Dewatering Structures in High-Methane-Flux Continental Slope

Morita

Nakajima

Hanamura

2011

Submarine Mass Movements and Their Consequences

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Submarine slump sediments and related dewatering structures: Observations of 3D seismic data obtained for the continental slope off Shimokita Peninsula, NE Japan

Morita

Nakajima

Hanamura

2011

Jour. Geol. Soc. Japan

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Abstract:The results of a three-dimensional seismic survey of the continental slope off Shimokita Peninsula, NE Japan, reveal the detailed features of typical slumps and related fluid-migration paths in Pliocene and Quaternary formations. Dewatering structures, which are strongly dependent on the development of imbricate structures within slump sediments, acted to drain excess fluid that accumulated upon the slip planes related to slumping. Damped and dimmed refl ections in the dewatering structures and in the slumps indicate that the distribution of natural gas is strongly related to fluid circulation in and around the slump sediments. Slumping and dewatering structures are probably typical phenomena in such a continental slope of high methane fl ux.

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Unusual BSRs and methane activity off Shimokita Peninsula in the western North Pacific

Cited by 3 publications

References 2 publications

Change in slide direction of submarine landslides in the Pliocene‐Quaternary deposits near the Shimokita Peninsula, northeast Japan, using 3D seismic data

Change in slide direction of submarine landslides in the Pliocene‐Quaternary deposits near the Shimokita Peninsula, northeast Japan, using 3D seismic data

Possible Ground Instability Factor Implied by Slumping and Dewatering Structures in High-Methane-Flux Continental Slope

Submarine slump sediments and related dewatering structures: Observations of 3D seismic data obtained for the continental slope off Shimokita Peninsula, NE Japan

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