How do tsunami differ from other water waves?
Tsunamis are unlike the wind-generated waves on local lakes or coastal beaches, in that they are characterized as shallow-water waves, with long periods and wavelengths. The wind-generated swell like the one at a California beach spawned by a storm out in the pacific and rhythmically rolling in, one wave after another might have a period of about 10 seconds and a wavelength of 150 m. A tsunami, on the other hand, can have a wavelength in excess of 100 km and period on the order of one hour. As a result of their long wave lengths tsunami behave as shallow-water waves. A wave becomes a shallow water wave when the ratio between the water depth and its wave length gets very small. Shallow-water waves move at a speed that is equal to the square root of the product of the acceleration of gravity (9.8 m/s/s) and the water depth. This means, in the Pacific Ocean, where the typical water depth is about 4000m, a tsunami travels at about 200m/s, or over 700 700km/hr. Because the rate at which a w
