Pacific Tsunami Warning Center

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Tsunameter and buoys used by DART system

The Pacific Tsunami Warning Center (PTWC), operated by NOAA in Ewa Beach, Hawaii, USA, is one of two tsunami warning centers in the United States. 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 area of responsibility . It is also the regional (local) warning center for the State of Hawai'i. The other tsunami warning center is the West Coast/Alaska Tsunami Warning Center (WC/ATWC) in Palmer, Alaska, serving all coastal regions of Canada and the United States except Hawai'i.

PTWC was established in 1949, following the 1946 Aleutian Island earthquake and a tsunami that resulted in 165 casualties in Hawaii and Alaska. After the Indian Ocean tsunami, PTWC has extended its warning guidance to include the Indian Ocean, Caribbean and adjacent regions until regional capability is in place for these areas. These regional systems will form a global tsunami warning system once they are in operation.

The Center 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.

Depending on the seismic data, PTWC will issue the following type 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.

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.

[edit] Deep ocean tsunami detection

In 1995 the US National Oceanic and Atmospheric Administration 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]

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 acoustic modem. 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.