distribution pattern of tsunami
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We studied a distribution pattern of tsunami deposits beneath Lake Mochirippu, a lagoon fingering a few km from the coast with narrow entrance on the Pacific coast of eastern Hokkaido. Eastern Hokkaido has been suffered by tsunamis from Kuril subduction zone, and many tsunami deposits from historical and prehistoric tsunamis have been reported from coastal marshes and lagoons. However, detailed distributional pattern of the tsunami deposits has not been established. From over 100 cores in Mochirippu, we identified two prehistoric tsunami deposits. One is from 17th-century giant earthquake, and the other lower one is undated yet. Detailed sedimentological characteristics of the 17th-century tsunami deposit can be summarized as follows; The tsunami deposit can be subdivided into four units named Unit 1 to Unit 4 in ascending order. Unit 1 is composed of poorly sorted medium to fine sand containing many plant fragments and rip-up clasts, and erosionally overlies the peat or mud layers. Unit 2 is composed of well-sorted medium sand, and overlies Unit 1. This unit has coarsest sediments in the four units. Unit 3 gradationally overlies Unit 2, and is composed of fine alternation of plant fragment laminae and fine to very fine sand layers. Unit 4 gradationally overlies Unit 3, and is composed of sandy silt with plant fragment seams. This unit is gradationally covered by mud or peat. This tsunami deposit ranges several cm to 30 cm in thickness. This tsunami deposit extends at least about 2 km from the bay mouth, and shows landward decreases in the thickness.
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Title:
A Distribution Pattern of Tsunami Deposits in Inter-tidal Zone at Mochirippu, Eastern Hokkaido, JapanAuthors:
Kamataki, T.; Sawai, Y.; Satake, K.; Yamaguchi, M.; Shishikura, M.; Matsumoto, D.Affiliation:
AA(Active Fault Research Center, GSJ/AIST (National Institute of Advanced Industrial Science and Technology), Site C7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan [email protected]), AB(Active Fault Research Center, GSJ/AIST (National Institute of Advanced Industrial Science and Technology), Site C7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan ;), AC(Active Fault Research Center, GSJ/AIST (National Institute of Advanced Industrial Science and Technology), Site C7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan ;), AD(Graduate School of Frontier Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan ;), AE(Active Fault Research Center, GSJ/AIST (National Institute of Advanced Industrial Science and Technology), Site C7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan ;), AF(Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto, 606-8502 Japan ;)Publication:
American Geophysical Union, Fall Meeting 2004, abstract id. T13C-1388Publication Date:
12/2004Origin:
AGUKeywords:
3022 Marine sediments: processes and transportBibliographic Code:
2004AGUFM.T13C1388K
Abstract
We studied a distribution pattern of tsunami deposits beneath Lake Mochirippu, a lagoon fingering a few km from the coast with narrow entrance on the Pacific coast of eastern Hokkaido. Eastern Hokkaido has been suffered by tsunamis from Kuril subduction zone, and many tsunami deposits from historical and prehistoric tsunamis have been reported from coastal marshes and lagoons. However, detailed distributional pattern of the tsunami deposits has not been established. From over 100 cores in Mochirippu, we identified two prehistoric tsunami deposits. One is from 17th-century giant earthquake, and the other lower one is undated yet. Detailed sedimentological characteristics of the 17th-century tsunami deposit can be summarized as follows; The tsunami deposit can be subdivided into four units named Unit 1 to Unit 4 in ascending order. Unit 1 is composed of poorly sorted medium to fine sand containing many plant fragments and rip-up clasts, and erosionally overlies the peat or mud layers. Unit 2 is composed of well-sorted medium sand, and overlies Unit 1. This unit has coarsest
sediments in the four units. Unit 3 gradationally overlies Unit 2, and is composed of fine alternation of plant fragment laminae and fine to very fine sand layers. Unit 4 gradationally overlies Unit 3, and is composed of sandy silt with plant fragment seams. This unit is gradationally covered by mud or peat. This tsunami deposit ranges several cm to 30 cm in thickness. This tsunami deposit extends at least about 2 km from the bay mouth, and shows landward decreases in the thickness
A Distribution Pattern of Tsunami Deposits in Inter-tidal Zone at Mochirippu, Eastern Hokkaido, JapanAuthors:
Kamataki, T.; Sawai, Y.; Satake, K.; Yamaguchi, M.; Shishikura, M.; Matsumoto, D.Affiliation:
AA(Active Fault Research Center, GSJ/AIST (National Institute of Advanced Industrial Science and Technology), Site C7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan [email protected]), AB(Active Fault Research Center, GSJ/AIST (National Institute of Advanced Industrial Science and Technology), Site C7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan ;), AC(Active Fault Research Center, GSJ/AIST (National Institute of Advanced Industrial Science and Technology), Site C7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan ;), AD(Graduate School of Frontier Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan ;), AE(Active Fault Research Center, GSJ/AIST (National Institute of Advanced Industrial Science and Technology), Site C7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan ;), AF(Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto, 606-8502 Japan ;)Publication:
American Geophysical Union, Fall Meeting 2004, abstract id. T13C-1388Publication Date:
12/2004Origin:
AGUKeywords:
3022 Marine sediments: processes and transportBibliographic Code:
2004AGUFM.T13C1388K
Abstract
We studied a distribution pattern of tsunami deposits beneath Lake Mochirippu, a lagoon fingering a few km from the coast with narrow entrance on the Pacific coast of eastern Hokkaido. Eastern Hokkaido has been suffered by tsunamis from Kuril subduction zone, and many tsunami deposits from historical and prehistoric tsunamis have been reported from coastal marshes and lagoons. However, detailed distributional pattern of the tsunami deposits has not been established. From over 100 cores in Mochirippu, we identified two prehistoric tsunami deposits. One is from 17th-century giant earthquake, and the other lower one is undated yet. Detailed sedimentological characteristics of the 17th-century tsunami deposit can be summarized as follows; The tsunami deposit can be subdivided into four units named Unit 1 to Unit 4 in ascending order. Unit 1 is composed of poorly sorted medium to fine sand containing many plant fragments and rip-up clasts, and erosionally overlies the peat or mud layers. Unit 2 is composed of well-sorted medium sand, and overlies Unit 1. This unit has coarsest
sediments in the four units. Unit 3 gradationally overlies Unit 2, and is composed of fine alternation of plant fragment laminae and fine to very fine sand layers. Unit 4 gradationally overlies Unit 3, and is composed of sandy silt with plant fragment seams. This unit is gradationally covered by mud or peat. This tsunami deposit ranges several cm to 30 cm in thickness. This tsunami deposit extends at least about 2 km from the bay mouth, and shows landward decreases in the thickness
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