How the Tsunami Alert System Works

Tsunami alert systems are designed to identify earthquakes likely to produce tsunamis, detect tsunamis as early as possible and warn the affected public when a tsunami is likely to hit the area. The alert system includes detection, analysis and communication. Some parts of the world have extensive alert systems, while others are building new systems. Only a few parts of the world have no tsunami alert system at all.

How it works

A network of earthquake sensors and seismographs provides precise tectonic information on the location and intensity of an earthquake. A complementary network of ocean buoys provides further information on changes in sea level. The most sophisticated of these are effectively seafloor and sea surface observatories. GPS links provide precise geographical location. Together, these systems can quickly identify a newly generated tsunami and provide crucial information about its direction, speed and energy.

Once the earthquake or tsunami has been identified and analyzed, the communications infrastructure takes over. This part of the tsunami alert system issues appropriately scaled tsunami alarms to the regions under threat. The issued warnings will include the tsunami’s estimated time of arrival and likely height at locations covered by the warning.

Finally, any tsunami alarm must be effectively communicated to the public. Parts of this system may include public visual displays, sirens, smartphone messages, or an automated calling system which may interrupt previous calls. Bulletins may be sent to local media. All current warnings are also displayed on the tsunami alert system’s webpage.

For subduction zones which are just offshore, the amount of warning time may be 5 minutes or less. However, a tsunami’s reach is ocean-wide and in a few cases worldwide. With an effective tsunami warning system, most other locations which could be affected by that tsunami will probably have several hours advance notice that a tsunami is on its way.

Worldwide coverage

The most comprehensive tsunami alert systems in the world are located around the Ring of Fire. The Pacific Tsunami Warning Center operates out of Hawaii, and is complemented in North America by the West Coast and Alaska Tsunami Warning Center. In Japan, this is supplemented by an earthquake early warning system, which can provide up to a 1-minute warning for a severe earthquake. Japan also has the best public communications for earthquake and tsunami alerts of any country in the world.

In Indonesia and the Indian Ocean, tsunamis are monitored by the Distant Early Warning System (DEWS). In addition, the German-Indonesian Tsunami Early Warning System is an attempt to give better coverage to Indonesia and similar locations where tsunamis won’t strike almost immediately, but will still probably hit within 20 minutes. It issues alerts within 5 minutes, followed by either an update or a cancelation.

The Atlantic Ocean and Caribbean Sea are susceptible to tsunamis. However, as of the time of writing, there is no comparible tsunami warning system for these regions.