A Numerical Study of Tsunami Generation by Horizontal Displacement of Sloping Seafloor

Tsunamis are generated primarily by the vertical displacement of the seafloor if the seafloor is flat. If the seafloor is slanted, the horizontal motion also contributes to the generation of tsunamis. A previous study proposed that such effects can be estimated by simply calculating the elevation of water due to the horizontal displacement of the slope. Two more studies later argued that the horizontal motion also results in horizontal momentum of the water, which amplifies the tsunami generation. In this study, we numerically simulate the tsunami generation process of flat and sloping seafloor. It is found that, for the flat seafloor, the initial water elevation equals the vertical seafloor displacement. For the sloping seafloor, the initial water elevation deviates from the vertical seafloor displacement, and the difference can be accurately evaluated by the horizontal seafloor displacement. Thus, the initial horizontal momentum of the water is negligible for tsunami generation.