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.
These earthquakes occur anywhere from 60 miles to 12,000 miles. So over there is where you can get a range of times from as little as 5 minutes to as much as 24 hours! So, the average time is about 6 hours, but can be as short as 5 minutes or as long as 24 hours. The time to react simply depends on whether or not a computer was able to detect the earthquake. It's very hard to know how much time you have to react after an earthquake creates a tsunami.