Tsunami Modeling for the Deep Sea and Inside Focal Areas

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This article reviews tsunami modeling and its relation to recent developments of deep-ocean observations. Unlike near-coast observations, deep-ocean observations have enabled the capture of short-wavelength dispersive tsunamis and reflected waves from the coast. By analyzing these waves, researchers can estimate tsunami sources and earthquake slip distributions more reliably with higher spatial resolution. In addition, fractional tsunami speed reduction due to the elasticity of the Earth medium is now clearly detected. Densely and widely distributed tsunami sensors make it possible to observe tsunamis inside the earthquake focal area, and understanding tsunami generation mechanisms is increasingly important. In order to describe the generation field, we should consider seismic waves overlapping tsunami signals in addition to vertical and horizontal displacements at the sea bottom. The importance of elastic dynamics, in addition to fluid dynamics, is increasing in order for researchers to fully understand tsunami phenomena using the new offshore and inside focal area observations. ▪ Deep-ocean observations have advanced tsunami propagation modeling. ▪ New deep-ocean observations in earthquake focal areas are expected to detect in situ tsunami generation caused by megathrust earthquakes. ▪ The importance of elastic dynamics, in addition to fluid dynamics, is increasing to help researchers fully understand mechanics in tsunami generation and propagation. ▪ Tsunami modeling including earthquake rupture and seismic waves contributes to mega-thrust earthquake investigation and disaster mitigation.