The massive security operation surrounding Barack Obama's inauguration showed that he will be the most protected president in the history of the United States. Photo: REUTERS.
The physics of a tsunami. Tsunamis can have wavelengths ranging from 10 to 500 km and wave periods of up to an hour. As a result of their long wavelengths, tsunamis act as shallow-water waves. A wave becomes a shallow-water wave when the wavelength is very large compared to the water depth. where g is the acceleration due to gravity (= 9.8 m/s2) and H is the depth of water.
A shallow water wave is one that travels through water having a depth less than 1/20 of its wavelength. Knowing that the average Pacific Ocean depth is roughly three miles, oceanographers can determine the speed of the tsunami, and calculate the time it will take to travel between any two points. This information led to the development of travel-time charts that make it possible to predict the arrival time of a tsunami wherever it is generated.