Preferential formation of a slide plane in translational submarine landslide deposits in a Pleistocene forearc basin fill exposed in east-central Japan
Published:September 30, 2019
Masayuki Utsunomiya, Atsushi Noda, Makoto Otsubo, 2019. "Preferential formation of a slide plane in translational submarine landslide deposits in a Pleistocene forearc basin fill exposed in east-central Japan", Subaqueous Mass Movements and their Consequences: Assessing Geohazards, Environmental Implications and Economic Significance of Subaqueous Landslides, D.G. Lintern, D.C. Mosher, L.G. Moscardelli, P.T. Bobrowsky, C. Campbell, J. Chaytor, J. Clague, A. Georgiopoulou, P. Lajeunesse, A. Normandeau, D. Piper, M. Scherwath, C. Stacey, D. Turmel
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Tephra beds are considered to be potential failure planes for submarine landslides. Here, we report on an example of a coarse-ash/lapilli-tuff bed influencing translational slides. The studied mass-transport deposit (MTD) is intercalated in the Pleistocene forearc basin fill exposed in east-central Japan. This MTD consists of stacked siltstone blocks resulting from repeated imbricate thrusts branching from the décollement. The basal slide plane is located immediately below a pumice-rich coarse ash/lapilli-tuff bed. The material comprising the slip zone is injected into the overlying coarse-ash/lapilli-tuff bed, suggesting an upwards escape of excess porewater that resulted from elevated pore pressure. To explain this mode of occurrence, we propose that the detachment preferentially occurred at the top and base of the coarse-ash-tuff-rich interval which appears to have been stronger relative to the adjacent silt-dominated interval. The pumiceous coarse-ash and lapilli-tuff bed behaved as a rigid plate on top of the high-pore-pressure slip zone, which sustained the translational slide on the gentle continental slope. Therefore, in translational submarine landslides, the preferential formation of a slide plane is caused by differing frictional resistances in the layered sediments.
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Subaqueous Mass Movements and their Consequences: Assessing Geohazards, Environmental Implications and Economic Significance of Subaqueous Landslides
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The challenges facing submarine mass movement researchers and engineers are plentiful and exciting. This book follows several high-profile submarine landslide disasters that have reached the world's attention over the past few years. For decades, researchers have been mapping the world's mass movements. Their significant impacts on the Earth by distributing sediment on phenomenal scales is undeniable. Their importance in the origins of buried resources has long been understood. Their hazard potential ranges from damaging to apocalyptic, frequently damaging local infrastructure and sometimes devastating whole coastlines. Moving beyond mapping advances, the subaqueous mass movement scientists and practitioners are now also focussed on assessing the consequences of mass movements, and the measurement and modelling of events, hazard analysis and mitigation. Many state-of-the-art examples are provided in this book, which is produced under the auspices of the United Nations Educational, Scientific and Cultural Organisation Program S4SLIDE (Significance of Modern and Ancient Submarine Slope LandSLIDEs).