Japan Geoscience Union Meeting 2023

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[J] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS16] Tsunami deposit

Tue. May 23, 2023 1:45 PM - 3:15 PM 106 (International Conference Hall, Makuhari Messe)

convener:Masaki Yamada(Department of Geology, Faculty of Science, Shinshu University), Takashi Ishizawa(International Research Institute of Disaster Science, Tohoku University), Koichiro Tanigawa(Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology), RYO NAKANISHI(Atmosphere and Ocean Research Institute, The University of Tokyo), Chairperson:Masaki Yamada(Department of Geology, Faculty of Science, Shinshu University), Koichiro Tanigawa(Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology)

2:30 PM - 2:45 PM

[MIS16-04] Geological evidence of coastal erosion generated with unusually large tsunamis in a beach ridge plain, eastern Hokkaido

*Yuki Sawai1, Toru Tamura1, Yumi Shimada1, Koichiro Tanigawa1 (1.National Institute of Advanced Industrial Science and Technology)

Keywords:Tsunami, Erosion, Kuril trench

Scour ponds generated from unusually large tsunamis reamed out a beach ridge in Kiritappu marsh, on the Pacific coast of Hokkaido. Ten scour ponds were imaged by photogrammetry as elongate topographic depressions. GPR and observation of sediment samples show that the ponds are underlain by unconformities. Sediment samples in the ponds contain peat and volcanic ash layers. Radiocarbon ages of plant macrofossils obtained from sediment samples just above peat-over-sand contact suggest that the scouring occurred during tsunamis generated by spatially extensive thrust ruptures along the southern Kuril trench.