Numerical modeling of the 2011 Tohoku-oki tsunami in the offshore and onshore of Sendai Plain, Japan

This paper examines the results of a numerical modeling of the 2011 Tohoku-oki earthquake tsunami to investigate its offshore propagation and inundation along a shore-normal transect located in the center of the Sendai Plain. The inundation distance, flow depth, and flow speed were compared with the available data measured during a post-tsunami field survey and estimated from the video records. The calculated inundation distance reached 4.5–5.5 km from the coastline, which is comparable to the actual inundation distance. The variation of tsunami heights from 2.4–6 m and flow speeds from 3.4–6.2 m/s along the transect is generally consistent with the measured heights and estimated speeds. The waveform on the beach showed that the wave train was composed of a high (10–11 m) first wave followed by low (~ 4 m) waves. Considering the waveform and the topographic change, the erosion of the beach and the sedimentation inland are explained mainly by the first wave. In addition, the calculated flow speed and friction velocities in the offshore may account for the formation of the possible tsunami deposits, which were reported recently by a sea-bottom survey. The modeling results are generally consistent with the available data and are considered to be useful for understanding the inundation pattern and sedimentation process of the Tohoku-oki tsunami on the Sendai Plain.