How Are Tsunamis Detected?

To help identify and predict the size of a tsunami, scientists can look at the size and type of the underwater earthquake that precedes it. That is often the first information they receive, because seismic waves travel faster than tsunamis. 

This information is not always helpful, however, because a tsunami can arrive within minutes after the earthquake that triggered it.
And not all earthquakes create tsunamis, so false alarms can and do happen.
That’s where special open-ocean tsunami buoys and coastal tide gauges can help—by sending real-time information to tsunami warning centers in Alaska and Hawaii. In areas where tsunamis are likely to occur, community managers, educators and citizens are being trained to provide eye-witness information that is expected to aid in the prediction and detection of tsunamis.
In the United States, NOAA has primary responsibility for reporting tsunamis and has created a Center for Tsunami Research.
Following the Sumatra Tsunami in 2004, NOAA stepped-up its efforts to detect and report tsunamis by:

• Developing tsunami models for at-risk communities
• Staffing NOAA warning centers around the clock
• Expanding the warning coverage area
• Deploying Deep-ocean Assessment and Report of Tsunamis (DART) buoy stations
• Installing sea level gauges
• Offering expanded community education through the TsunamiReady program

To see where tsunamis have been reported, check NOAA’s Interactive Map of Historical Tsunami Events.