ИСТИНА

The subject of this study is the comparative analysis of the 2D and 3D approaches to the tsunami simulation. For this analysis an outer-rise earthquake along the Japan Trench was chosen. The vertical bottom displacement caused by this earthquake produces short-wavelength waves, so in this case the 2D model may not be able to predict tsunami accurately. We performed 2D tsunami simulations with the use of the JAGURS code [1], based on the nonlinear shallow water equations with Boussinesq terms. In these 2D simulations we ignored the horizontal displacement effect [2], but we applied the Kajiura filter [3] in estimating the sea surface displacements from the vertical displacement of the seafloor. In the 3D tsunami simulation we used Combined Potential Tsunami Model (CPTM), based on the linear wave equation with respect to the flow velocity potential for the homogenius compressible ocean [4]. The equations of the 3D model were written in the curvilinear non-orthogonal depth-normalized sigma-spherical coordinate system. The 2D and 3D results coincides well, but in some points there are small discrepancies between them. To find the cause of these discrepancies we performed additional numerical experiments. First numerical experiment was focused on the tsunami generation process and especially on the applying of the Kajiura filter in the 2D model. In the second numerical experiment we studied the role of the number of the vertical layers in 3D calculations in reproducing the dispersive effects of the tsunami propagation. This work was supported by the Russian Foundation for Basic Research (Projects 20-35-70038, 19-05-00351, 20-07-01098). References: 1. Baba, T., Allgeyer, S., Hossen, J., Cummins, P.R., Tsushima, H., Imai, K., Yamashita, K., Kato, T., 2017. Accurate numerical simulation of the far-field tsunami caused by the 2011 Tohoku earthquake, including the effects of Boussinesq dispersion, seawater density stratification, elastic loading, and gravitational potential change. Ocean Model. 111, 46–54. https://doi.org/10.1016/j.ocemod.2017.01.002. 2. Tanioka, Y., Satake, K., 1996. Tsunami generation by horizontal displacement of ocean bottom. Geophysical Research Letters, 23(8), 861–864. https://doi.org/10.1029/96GL00736. 3. Kajiura, K., 1963. The leading wave of a tsunami. Bull. Earthquake Res., Inst. Univ. Tokyo 41, 535–571. 4. Sementsov, K. A., Nosov, M. A., Kolesov, S. V., Karpov, V. A., Matsumoto, H., Kaneda, Y., 2019. Free Gravity Waves in the Ocean Excited by Seismic Surface Waves: Observations and Numerical Simulations. Journal of Geophysical Research: Oceans, 124(11), 8468-8484.