Figure 3. Image showing the characteristics of a tsunami as it passes through the mid-ocean and approaches a coastline. Note the high speed (>400 mph in 4000 m depth), large wavelength (213 km), and low amplitude (usually a meter or less) of the wave as it passes through deep water. Because of their large wavelength and deep water (thus low amplitude), most tsunamis pass in the mid-ocean unnoticed. However, as the wave encounters shallower water, its velocity slows, wavelength decreases, and its amplitude increases (image from GlobalSecurity.org).
Last updated on October 6, 2005