What is the highest rate a tsunami can go?

Answer 1

In the deep ocean a tsunami wave travels at well over 800 kilometres per hour (500 mph). As the tsunami approaches the coast and the waters become shallow its velocity slows to below 80 kilometres per hour (50 mph) and it becomes taller.

Answer 2

Tsunami waves can travel at speeds up to 500-600 miles per hour (800-960 kilometers per hour) in the open ocean, although they can slow down as they approach shallow water near Coastlines.