Altezza dell’onda e propagazione in direzione e nel tempo. Clic sull’immagine per vederla in movomento. La velocità di 400 km orari non è da poco.

In deep water, tsunami move about 400 km/hr and the surface displacement (wave height) is relatively small. That’s why, if it’s known that a tsunami is on its way, boats will leave harbor and head out to deep water. As the tsunami approaches the shore, it slows and the wave heights increase. The Japanese word tsunami actually means “harbor wave”, because it is only close to shore that it is easily spotted.

via RDF