Models of Tsunami Sources of Seismic Origin

Abstract

The review presents basic concepts of earthquake sources, including empirical relationships that link the size of the fault area, the slip value, and the energy of seismic waves with the earthquake’s magnitude. The complex and ambiguous relationship between earthquake magnitude and tsunami intensity according to the Soloviev–Imamura scale is discussed. Some empirical relationships connecting the size of the tsunami source, the height of the initial disturbance of the water surface, and the energy of the tsunami with the earthquake’s magnitude are provided. Based on the analytical solution to the problem of gravity wave generation by bottom movements and physical assessments, it is shown that the leading role in the generation of tsunami waves by seismic bottom movements belongs to residual bottom displacements which occur in the direction normal to the bottom surface. A model is described that approximates the tsunami-generating earthquake source as a rectangular fault area, as well as an approach to describing tsunami generation using data on the structure of slip distribution in the earthquake source. Based on data on the structure of slip distribution in the sources of strong underwater earthquakes (200 sources), empirical relationships between the amplitude of bottom displacement in the tsunami source, the displaced water volume, and tsunami energy with the earthquake’s moment magnitude have been established. It is shown that the fraction of the earthquake’s energy transferred to the tsunami increases with magnitude and ranges from 0.004\(\%\) (at \(M_{W}=7\)) to 0.1\(\%\) (at \(M_{W}=9\)). It is shown that horizontal displacements of the bottom, as a rule, provide an additional contribution to the displaced water volume and energy of the tsunami.