The 1960 Valdivia earthquake ( '' M '' w 9.5 ) , 1964 Alaska earthquake ( '' M '' w 9.2 ) , 2004 Indian Ocean earthquake ( '' M '' w 9.2 ) , and 2011 Tōhoku earthquake ( '' M '' w9 .0 ) are recent examples of powerful megathrust earthquakes that generated tsunamis ( known as teletsunamis ) that can cross entire oceans . Smaller ( '' M '' w 4.2 ) earthquakes in Japan can trigger tsunamis ( called local and regional tsunamis ) that can devastate stretches of coastline , but can do so in only a few minutes at a time
1964 Alaska earthquake
1964 Alaska earthquake
Tsunami