Hydro-sedimentological study on running-up currents by the 2011 Tohoku-Oki tsunami

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I have studied the tsunami deposits produced by the 869 Jogan and the 2011 Tohoku-Oki earthquake tsunamis for the purpose of making clear the hydro-sedimentological effect of vegetation and micro-topography on running-up currents. Micropareontological data were very useful for identifying the origin of sediments by the tsunamis. The results infer the laminated sand layer found at the base of the tsunami deposits to represent deposition under supercritical flow conditions. Each layer of the laminated sand shows inverse grading, and lamina sets display a stack of thin layers, which are produced by flows with high grain concentrations. The dominant occurrence of saltwater and brackish water species and the high percentage of perfect frustules indicate that the laminated sand was deposited by flows of water originating in the foreshore. The results has confirmed the hydrogeological framework of running-up currents by the 2011 Tohoku-Oki tsunami.