Tsunami warning system
From Freepedia
A tsunami warning system is a system to detect tsunamis and issue warnings to prevent loss of life. It consists of two equally important components: a network of sensors to detect tsunamis and a communications infrastructure to issue timely alarms to permit evacuation of coastal areas. See How the Tsunami Warning System works.
Many areas around the Pacific, notably Japan, Hawaii, French Polynesia, Alaska and the Pacific coasts of South America, have tsunami warning systems and evacuation procedures in case of a serious tsunami. However other oceans do not, and this contributed to major loss of life after the 2004 Indian Ocean tsunami. In the aftermath of this disaster, it is very likely that warning systems will be put in place in the Indian Ocean, Atlantic Ocean and Caribbean, and plans have started for an International Early Warning Programme. See also Indian Ocean Tsunami Warning System.
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Types
There are two distinct types: international tsunami warning systems, and regional warning systems. Both depend on the fact that, while tsunamis travel at between 500 and 1,000 km/h in open water, earthquakes can be detected almost at once as seismic waves travel with a typical speed of 5 km/s. This gives time for a tsunami forecast to made and warnings to be issued to threatened areas, if warranted. The first rudimentary system to alert communities of an impending tsunami was attempted in Hawaii in the 1920s. More advanced systems were developed in the wake of the April 1, 1946 and May 23, 1960 tsunamis which caused massive devastation in Hilo, Hawaii.
International tsunami prediction for the Pacific Ocean and early warning is over-seen by the US Pacific Tsunami Warning Center (PTWC) operated by NOAA in Ewa Beach, Hawaii. This centre was established in 1949, following the 1946 Aleutian Island earthquake and a tsunami that resulted in 165 casualties on Hawaii and Alaska. International coordination is achieved through the International Coordination Group for the Tsunami Warning System in the Pacific, established by the Intergovernmental Oceanographic Commission of UNESCO.
Regional warning systems
Regional (or local) warning system centres use seismic data about nearby earthquakes to determine if there is a possible local threat of a tsunami. Such systems are capable of issuing warnings to the general public (via public address systems and sirens) in less than 15 minutes. Although the epicenter and moment magnitude of a underwater quake and the probable tsunami arrival times can be quickly calculated, it is almost always impossible to know whether underwater ground shifts have occurred which will result in tsunami waves. As a result, false alarms can occur with these systems, but due to the highly localised nature of these extremely quick warnings, disruption is small.
International warning systems
The international Pacific Tsunami Warning Center also uses seismic data as its starting point, but then takes into account oceanographic data when calculating possible threats. Tide gauges in the area of the earthquake are checked to establish if a tsunami wave has formed. The centre then forecasts the future of the tsunami, issuing warnings to at-risk areas all around the Pacific basin if needed. There are never false alarms — if the PTWC issues a tsunami warning for a particular area, the wave is already on its way and will hit. As it takes more time for tsunamis to travel trans-oceanic distances, the PTWC can afford to take the time to make sure of its forecasts.
Deep ocean tsunami detection
In 1995 the US National Oceanic and Atmospheric Administration (NOAA) began developing the Deep-ocean Assessment and Reporting of Tsunamis (DART) system. By 2001 an array of six stations had been deployed in the Pacific Ocean. [1]
Tsunami happened in Minicoy on 12th December 2005.
Beginning in 2005, as a result of heightened awareness due to the tsunamis caused by the 2004 Indian Ocean earthquake, plans were announced to add 32 more DART buoys to be operational by mid-2007. [2]
These stations give detailed information about tsunamis while they are still far off shore. Each station consists of a sea-bed bottom pressure recorder (at a depth of about 6000 m) which detects the passage of a tsunami and transmits the data to a surface buoy via sonar. The surface buoy then radios the information to the PTWC via the GOES satellite system. The bottom pressure recorder lasts for two years while the surface buoy is replaced every year. The system has considerably improved the forecasting and warning of tsunamis in the Pacific.
Conveying the warning
Detection and prediction of tsunamis is only half the work of the system. Of equal importance is the ability to warn the populations of the areas that will be effected. All tsunami warning systems feature multiple lines of communications (such as e-mail, fax, radio and telex, often using hardened dedicated systems) enabling emergency messages to be sent to the emergency services and armed forces, as well to population alerting systems (eg sirens).
Shortcomings
No system can protect against a very sudden tsunami. A devastating tsunami occurred off the coast of Hokkaido in Japan as a result of an earthquake on July 12, 1993. As a result, 202 people on the small island of Okushiri, Hokkaido lost their lives, and hundreds more were missing or injured. This tsunami struck just three to five minutes after the quake and most victims were caught while fleeing for higher ground and secure places after surviving the earthquake.
While there remains the potential for sudden devastation from a tsunami, warning systems can be effective. For example if there were a very large subduction zone earthquake (magnitude 9.0) off the west coast of the United States, people in Japan, for example, would have more than 12 hours (and likely warnings from warning systems in Hawaii and elsewhere) before any tsunami arrived, giving them some time to evacuate areas likely to be affected.
See also
External links
- Space Applications for Disaster Monitoring
- How does the Tsunami Warning System Work? from the NOAA Tsunami website
- Pacific Tsunami Warning Centre
- West Coast and Alaska Coast regional Warning Centre
- DART
- Tsunami Alarm System to mobile phones for everybody
