2023 Volume 79 Issue 17 Article ID: 23-17032
On January 15, 2022, at around 13:00 JST, a massive eruption occurred at Hunga Tonga-Hunga Ha’apai volcano in the Tonga Islands, South Pacific Ocean. The eruption was accompanied by rapid atmospheric pressure changes and tsunamis along the Pacific coast. Along the Japanese coast, tsunami waves were observed several hours before the expected arrival time due to the pressure change of about 2 hPa, and the subsequent tsunami heights exceeded 1 m at some stations. These are caused by the pressure waves that excited the sea surface waves, but the external force factor that can fully explain the maximum amplitude has not been clarified. This study performed tsunami simulations for the area around Japan and estimated the factors that could explain the maximum amplitude of the tsunami along the coast of Japan by comparing the results of the simulations under several patterns of external force conditions with the observed records. The results showed that a component corresponding to the resonant period caused continuous amplification in bays along the coast of the Tohoku region. On the other hand, in Amami and Shikoku, the amplification mechanism generated by the propagation on the water surface may have contributed to the amplification and to the excitation of the water surface by the external barotropic force.
