Tsunami change significantly as they propagate, principally due to water depth variations, but they can be described in terms of wavelength, period, velocity and amplitude.

		Devastation of Pagaraman, on Babi Island, Indonesia where 700 were killed in 1992.

The amplitudes of tsunamis decrease with distance from the source owing to geometrical factors (divergence of waves on the surface of the Earth) and dispersion (energy loss, mainly in shallow water).

Once a tsunami arrives at a coastline, the energy that has been carried by the waves from the source is liberated as kinetic and potential energy. This movement of water onto the land is sometimes tranquil but is more commonly violent, with large breaking waves at or close to the shore converting into turbulent bores or surges of water. Tsunamis cause losses by a wide variety of direct and indirect processes, some of which produce losses well outside the inundation zone.