Official Tsunami Warnings

Tsunami warning systems detect earthquakes large enough to cause a tsunami and send warning bulletins before the waves arrive so that local authorities can evacuate vulnerable populations.

The United States operates two tsunami warning centers, the Pacific Tsunami Warning Center in Hawaii covers Hawaii, the U.S. Pacific territories, and provides guidance to many other counties. The National Tsunami Warning Center has the responsibility of warning Canada and the rest of the United States, including California. 

Official tsunami warnings are most effective when the tsunami source is more than 1,000 miles away, such as Alaska, Japan, or Chile. If the earthquake is located on a local fault, such as the Cascadia Subduction Zone, there is too little time for the National Tsunami Warning Center to get a warning to you. Ground shaking that lasts for a long time or other natural warning signs will be your only warning during an earthquake you feel. Know what areas are hazardous and immediately head to high ground or away from the coast in these situations.

Based on earthquake size and location, the National Tsunami Warning Center will issue alerts corresponding to the relative tsunami threat:

Tsunami Alert Levels Graphic

More details

warning graphic triangle
Tsunami Warning – A tsunami warning is issued when a tsunami with the potential to generate widespread inundation is imminent, expected, or occurring. Warnings alert the public that dangerous coastal flooding accompanied by powerful currents is possible and may continue for several hours after initial arrival. Warnings alert emergency management officials to take action for the entire tsunami hazard zone. Appropriate actions to be taken by local officials may include the evacuation of low-lying coastal areas, and the repositioning of ships to deep waters when there is time to safely do so. Warnings may be updated, adjusted geographically, downgraded, or canceled based on updated information and analysis.


tsunami advisory triangle
Tsunami Advisory – A tsunami advisory is issued when a tsunami with the potential to generate strong currents or waves dangerous to those in or very near the water is imminent, expected, or occurring. The threat may continue for several hours after initial arrival, but significant inundation is not expected for areas under an advisory. Appropriate actions to be taken by local officials may include closing beaches, evacuating harbors and marinas, and the repositioning of ships to deep waters when there is time to safely do so. Advisories may be updated, adjusted geographically, upgraded to a warning, or cancelled based on updated information and analysis.

 
Tsunami watch triangle
Tsunami Watch – A tsunami watch is issued when a tsunami may later impact the watch area. The watch may be upgraded to a warning or advisory or canceled based on updated information and analysis. Emergency management officials and the public should prepare to take action. 


 
Tsunami Information Statement – A tsunami information statement is issued when an earthquake or tsunami has occurred of interest to the message recipients. In most cases, information statements are issued to indicate there is no threat of a destructive basin-wide tsunami and to prevent unnecessary evacuations. Information statements for distant events requiring evaluation may be upgraded to a warning, advisory, or watch based on updated information and analysis.

Previous » Learn about Natural Warnings

The National Tsunami Warning Center also issues tsunami statements when an earthquake occurs near the coast that people may have felt, but does not pose a tsunami threat.

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Demo of Sound

  Listen to an explanation of what official tsunami messages mean