The first rudimentary system to alert communities of an impending tsunami was attempted in Hawaii in the 1920s . More advanced systems were developed in the wake of the April 1 , 1946 ( caused by the 1946 Aleutian Islands earthquake ) and May 23 , 1960 ( caused by the 1960 Valdivia earthquake ) tsunamis which caused massive devastation in Hilo , Hawaii . While tsunamis travel at between 500 and 1,000 km/h ( around 0.14 and 0.28 km/s ) in open water , earthquakes can be detected almost at once as seismic waves travel with a typical speed of 4 km/s ( around 14,400 km/h ) . This gives time for a possible tsunami forecast to be made and warnings to be issued to threatened areas , if warranted . Until a reliable model is able to predict which earthquakes will produce significant tsunamis , this approach will produce many more false alarms than verified warnings
1946 Aleutian Islands earthquake
1946 Aleutian Islands earthquake
Tsunami warning system