Influence of Edge Waves on Tsunami Characteristics along Kujukuri Beach, Japan

The 2011 Tohoku Earthquake and Tsunami generated a massive tsunami that devastated Kujukuri Beach in Chiba Prefecture, Japan. The possibility that edge waves were involved in the propagation mechanism of the tsunami was investigated by using a numerical method. To detect the components of edge waves, the fluctuations of the simulated sea level, the variations of the power spectral and the phase, coherences, as well as the dispersed relations of the wavelength and the period, were analyzed. As a result, it was possible to conclude that there is a high probability that edge waves could have propagated around this coastline. In addition, to analyze the various types of edge waves that could be expected three additional earthquake scenarios were considered, each of them with a different magnitude and epicenter: The 1896 Sanriku Earthquake, the 1677 Empo Boso-oki Earthquake, and the 1703 Genroku Kanto Earthquake. This comparison indicates that there is a particular risk that edge waves can be generated by large earthquakes with their epicenter in the northern part of the Japan Trench.