Physics of tsunami

In deep ocean
 

The speed of tsunami is proportionate to the square root of the ocean depth. In the middle 

of the ocean(4000m),  a tsunami travels with a speed of 200m/s of over 700km/hr.   It takes 
only about 6-7 hours a tsunami generated in Gulf of Alaska to reach to Hawaii.
 

Their wavelengths are hundreds of kilometers and their heights are 1m or less, therefore 

tsunamis pass unnoticied by people in ships or planes in the region.
 
 

wcatwc.arh.noaa.gov

This map is showing travel time of a tsunami generated in Hawaii. Each band is for one hour.

At the coast
 

As a tsunami arrives the coast, the speed of the tsunami decreases with decreasing depth. But,

the change of total energy of the wave remains the same, therefore the height of  the wave grows.
 

A tsunami at the coast appears as a rapidly rising or falling tide or a series of breaking waves.

 

Runup(height) - the maximum height of the wave observed above a reference sea level