Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS11] tsunami deposit

Tue. May 22, 2018 9:00 AM - 10:30 AM 102 (1F International Conference Hall, Makuhari Messe)

convener:Tetsuya Shinozaki(Center for Research in Isotopes and Environmental Dynamics (CRiED), University of Tsukuba), Takashi Chiba(Maritime Disaster Prevention Center), Daisuke Ishimura(首都大学東京大学院都市環境科学研究科地理学教室), Chairperson:Shinozaki Tetsuya(Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba)

9:45 AM - 10:00 AM

[MIS11-04] Grain size feature and there origin of 3.11 Tsunami deposit at Hirota bay, Iwate pref.

*Yuka Yokoyama1, Izumi Sakamoto1, Kosuke Tsutsumi1, Rihoko Saito1, Naoki Haramiishi1 (1.School of Marine Science and Technology, Tokai University)

Keywords:Tsunami deposit, Sanriku coast, 2011Tohoku earthquake

The recent 2011 Tohoku earthquake affected Tohoku area and coastal area of Pacific coast were strongly damaged by Tsunami. A lot of bay of Sanriku coast became deposited new sediment composed by coarse-grained material (sand to sandy gravel sediments), and estimate of the sedimentation model about Tsunami deposit are carried out at coastal area. But, we didn’t understand about origin of Tsunami deposits at coastal area. So, in this study we will try to estimate the origin of Tsunami deposits using by grain size features.

We took the columnar core samples at water depth from 8 to 30 m. The columnar core samples were able to sectionalize into mainly two units by lithofacies, Unit1 (sand layer) and Unit2 (muddy layer) from the top, and some core have sand layer under the Unit3. Yokoyama et al. (2014) estimated Unit1 were 2011 Tsunami deposit, Unit2 were normal sediment in this bay, and Unit3 were paleo-event sediment. Unit1 were able to sectionalize into some sub-units by lithofacies and grain size analysis.

Correlation diagram of median diameter and sorting value show that Unit1 is different from Unit2 in distribution, and Unit1 distribute between Unit2 and coast sand. So, Unit1 are estimated to origin in Unit2 and coast sand. Especially, most coastal area core distribute at coastal sand area, it’s origin in coastal sand. Correlation diagram of median diameter and sorting value have possibility about estimate the source of supply field of Tsunami deposits. In presentation time, we will show about chemical analysis data about Tsunami deposit in addition to grain size feature.