Tsunami News & Photos

What is the difference between a Tsunami Watch and a Tsunami Warning?

A Tsunami Watch is automatically declared by the warning center for any earthquake having a magnitude of 7.5 or larger on the Richter scale (7.0 or larger in the Aleutian Islands) and located in an area where a tsunami can be generated. Notification of and Civil Defense agencies begins, followed by limited public announcements by the local media. Data from tidal gauge stations is awaited for confirmation of the actual existence of a tsunami.

Reports on wave activity from the tide-gauging stations nearest to the earthquake epicenter is requested by the warning center. If the stations report that there is no observed tsunami activity, the Tsunami Watch is canceled. If these stations report that a tsunami has been generated, a Tsunami Warning is issued for areas which may be impacted in the next hour. At this time the public is informed of the ensuing danger by the emergency broadcast system. Evacuation procedures are implemented, and sea going vessels are advised to head out to sea, where in deep waters they will not be affected by the tsunami.