TY - JOUR
T1 - Spatial thickness variability of the 2011 Tohoku-oki tsunami deposits along the coastline of Sendai Bay
AU - Goto, Kazuhisa
AU - Hashimoto, Kohei
AU - Sugawara, Daisuke
AU - Yanagisawa, Hideaki
AU - Abe, Tomoya
N1 - Funding Information:
We especially thank the agricultural division of Miyagi Prefecture, Midori-net Miyagi and K. Sasaki for providing the dataset for Sendai Plain. The copyright of the thickness dataset belongs to the Miyagi Prefecture and Midori-net Miyagi. We also thank anonymous reviewers for their valuable suggestions and comments. This research was supported by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (K. Goto, 22241042 ) for field survey and data analysis.
Publisher Copyright:
© 2014 Elsevier B.V.
PY - 2014/12/1
Y1 - 2014/12/1
N2 - Soon after the 2011 Tohoku-oki event, approximately 1300 tsunami deposit thickness data were collected spatially by the governors to cover the entire tsunami affected area (Sendai Plain) along the Sendai Bay coastline. This dataset, along with high-resolution and high-precision data of flow depth and pre-tsunami and post-tsunami elevation, enables us first to conduct a direct comparison of the sedimentation and erosion volumes as well as the tsunami hydrodynamic features (e.g., flow depth) and sediment thickness. The total balance of sedimentation and erosion volumes revealed that the volume of tsunami-deposited sediments can be explained roughly using the erosion volumes at the beach and sand dunes for sandy deposits and at rice paddy fields for muddy deposits. Both the flow depth and sediment thickness showed positive correlations with the distance from the shoreline while sediment thickness is no correlation to the elevation except in the zone closest to the shoreline where erosion is present. In addition, a statistical relation was found between the flow depth and sediment thickness. In fact, the frequency distribution of sediment concentration, defined here as the sediment thickness divided by the maximum flow depth at each survey site, fits well with the logarithmic normal distribution with geometric average of about 2%. This fit indicates that the tsunami deposits on the Sendai Plain can be explained generally if we simply assume that the saturated level of the sediment concentration in the flow is limited to about 2% on average, irrespective of the grain size. Such a simple explanation might be applicable only for the tsunami deposits on the Sendai Plain because the topography is remarkably flat and low. Therefore, the tsunami inundation process is relatively simple. Nevertheless, a possible relation between tsunami flow depth and sediment thickness suggested here would be very useful to consider the ideal sedimentary process of the tsunami deposits and to improve forward and inverse modelings.
AB - Soon after the 2011 Tohoku-oki event, approximately 1300 tsunami deposit thickness data were collected spatially by the governors to cover the entire tsunami affected area (Sendai Plain) along the Sendai Bay coastline. This dataset, along with high-resolution and high-precision data of flow depth and pre-tsunami and post-tsunami elevation, enables us first to conduct a direct comparison of the sedimentation and erosion volumes as well as the tsunami hydrodynamic features (e.g., flow depth) and sediment thickness. The total balance of sedimentation and erosion volumes revealed that the volume of tsunami-deposited sediments can be explained roughly using the erosion volumes at the beach and sand dunes for sandy deposits and at rice paddy fields for muddy deposits. Both the flow depth and sediment thickness showed positive correlations with the distance from the shoreline while sediment thickness is no correlation to the elevation except in the zone closest to the shoreline where erosion is present. In addition, a statistical relation was found between the flow depth and sediment thickness. In fact, the frequency distribution of sediment concentration, defined here as the sediment thickness divided by the maximum flow depth at each survey site, fits well with the logarithmic normal distribution with geometric average of about 2%. This fit indicates that the tsunami deposits on the Sendai Plain can be explained generally if we simply assume that the saturated level of the sediment concentration in the flow is limited to about 2% on average, irrespective of the grain size. Such a simple explanation might be applicable only for the tsunami deposits on the Sendai Plain because the topography is remarkably flat and low. Therefore, the tsunami inundation process is relatively simple. Nevertheless, a possible relation between tsunami flow depth and sediment thickness suggested here would be very useful to consider the ideal sedimentary process of the tsunami deposits and to improve forward and inverse modelings.
KW - 2011 Tohoku-oki tsunami
KW - Sendai Bay
KW - Tsunami deposit
UR - http://www.scopus.com/inward/record.url?scp=84914172606&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84914172606&partnerID=8YFLogxK
U2 - 10.1016/j.margeo.2013.12.015
DO - 10.1016/j.margeo.2013.12.015
M3 - Article
AN - SCOPUS:84914172606
SN - 0025-3227
VL - 358
SP - 38
EP - 48
JO - Marine Geology
JF - Marine Geology
ER -