Near shore modifications

As a tsunami nears the shoreUne, its height increases and becomes comparable with the water depth ( shallow water see footnote 27). The shallow water equations including the effect of bottom friction should be applied. The theory still assumes the hydrostatic pressure but it takes into consideration the finiteness of the wave amplitude. The second order phase velocity includes the effect of the elevation of the water surface. This effect causes the higher part of the wave to proceed faster. The frontal slope of the wave thus becomes steeper. If the velocity of the water particles at the front exceeds the local phase velocity, the water projects into the air consequently, a breaking bore is formed. 

Significant oscillations of a water body (seiches) can be excited by tsunamis. When the frequency of the incoming tsunami matches one of the local oscillation modes, resonant amplification leading to large motions of the water may occur. Oscillations of a water body also arise from the continuous application of an excitation either to the water column at an entrance or over the water surface. The maximum wave height can therefore often be observed not at the arrival of the first wave but after several waves. To evaluate the 

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