Tsunami Detection and Warning

How Are Tsunami's Detected?

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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. This 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

The DART system has been criticized, however, for its high failure rate.

It appears the buoys frequently degrade and stop functioning in the harsh marine environment. Sending a ship to service them is very expensive, and failed ones are not replaced promptly.

Detection Is Only Half the Battle

Once a tsunami is detected, that information has to be communicated effectively and rapidly to vulnerable communities.

In the event a tsunami is triggered right along the coastline, there is very little time for an emergency message to be relayed to the public. People living in earthquake-prone coastal communities should view any large earthquake as their warning to act immediately and head for higher ground. For earthquakes triggered far away, in the United States NOAA has a tsunami warning system which will alert the public via news outlets, television and radio broadcast, and weather radios. Some communities have outdoor siren systems which can be activated. 

Review NOAA's guidelines on how to respond to a tsunami warning. To see where tsunamis have been reported, check NOAA’s Interactive Map of Historical Tsunami Events.


Edited by Frederic Beaudry.