The Pacific Tsunami Warning Center (PTWC) is one of two

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explo ...

warning centers that are operated by

NOAA The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...

in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

. Headquartered on Ford Island, HI, the PTWC is part of an international tsunami warning system (TWS) program and serves as the operational center for TWS of the Pacific issuing bulletins and warnings to participating members and other nations in the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

area of responsibility. It is also the regional (local) warning center for the State of

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

. The other tsunami warning center is the National Tsunami Warning Center (NTWC) in Palmer, Alaska, serving all coastal regions of Canada and the United States except Hawaii, the Caribbean Sea and the Gulf of Mexico. The PTWC was established in 1949, following the 1946

Aleutian Island earthquake The 1946 Aleutian Islands earthquake occurred near the Aleutian Islands, Alaska on April 1, 1946. The shock had a Moment magnitude scale, moment magnitude () of 8.6, a Seismic_magnitude_scales#Tsunami_magnitude_scales, tsunami magnitude of 9.3, ...

and a tsunami that resulted in 165 casualties in Hawaii and

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

. The PTWC uses seismic data as its starting point, but then takes into account oceanographic data when calculating possible threats.

Tide Tides are the rise and fall of sea levels caused by the combined effects of the gravity, gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide t ...

gauges in the area of the earthquake are checked to establish if a tsunami has formed. The center then forecasts the future of the tsunami, issuing warnings to at-risk areas all around the Pacific basin if needed.

Bulletins

Depending on the seismic data, PTWC will issue the following types of bulletins: ;Tsunami Information Bulletin :At this time, though a threat exists, there is no evidence that a tsunami is making its way across the Pacific. ;Tsunami Watch :PTWC has determined the earthquake may very likely have created a tsunami and is advising parties to be alert as PTWC awaits tide data to support tsunami generation. A watch may be upgraded to an advisory or a warning. ;Tsunami Advisory :PTWC has determined the earthquake has created a tsunami with strong currents or waves dangerous to those in or very near the water. ;Tsunami Warning :PTWC finds conditions serious enough to issue immediate concern to parts of the Pacific. The message will include approximate arrival times for various parts of the Pacific.

Deep-ocean tsunami detection

In 1995,

began developing the

Deep-ocean Assessment and Reporting of Tsunamis Deep-ocean Assessment and Reporting of Tsunamis (DART) is a component of an enhanced tsunami warning system. By logging changes in seafloor temperature and pressure, and transmitting the data via a surface buoy to a ground station by satellit ...

(DART) system. By 2001, an array of six stations had been deployed in the

. Beginning in 2005, as a result of the tsunami caused by the

2004 Indian Ocean earthquake An earthquake and a tsunami, known as the Boxing Day Tsunami and, by the scientific community, the Sumatra–Andaman earthquake, occurred at 07:58:53 local time (UTC+7) on 26 December 2004, with an epicentre off the west coast of northern Suma ...

, plans were announced to add 32 more DART buoys to be operational by mid-2007. 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 1000–6000 m) which detects the passage of a tsunami and transmits the data to a surface

buoy A buoy () is a floating device that can have many purposes. It can be anchored (stationary) or allowed to drift with ocean currents. Types Navigational buoys * Race course marker buoys are used for buoy racing, the most prevalent form of yac ...

via acoustic modem. The surface buoy then radios the information to the PTWC via the

GOES Goes () is a city and municipality in the southwestern Netherlands on Zuid-Beveland, in the province of Zeeland. The city of Goes has approximately 27,000 residents. History Goes was founded in the 10th century on the edge of a creek: de Korte ...

satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...

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 Ocean.

Final transmission

Local populations in the United States of America receive tsunami information through radio and television receivers connected to the

Emergency Alert System The Emergency Alert System (EAS) is a national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via cable, satellite, or broadcast television, and both ...

, and in some places (such as Hawaii)

civil defense siren A civil defense siren, also known as an air-raid siren or tornado siren, is a siren used to provide an emergency population warning to the general population of approaching danger. It is sometimes sounded again to indicate the danger has pas ...

s and roving loudspeaker broadcasts from police vehicles. The public can subscribe to the

RSS feed RSS ( RDF Site Summary or Really Simple Syndication) is a web feed that allows users and applications to access updates to websites in a standardized, computer-readable format. Subscribing to RSS feeds can allow a user to keep track of many di ...

or email alerts from the PTWC web site, and the UNESCO site. Email and text messages are also available from the USGS Earthquake Notification Service which includes tsunami alerts.

References

External links

{{portal, Oceans, Tsunamis
US Tsunami Warning SystemNational Tsunami Warning CenterDARTHow the US Tsunami Warning System works
Warning systems Tsunami Earthquake and seismic risk mitigation Seismological observatories, organisations and projects Disaster preparedness in the United States Disaster preparedness in Oceania 1949 establishments in Hawaii