Pacific Tsunami Warning Center

Up until the late 1940s, the United States had no way to warn the public about tsunami threats. After the 1946 Aleutian Islands earthquake, which generated a tsunami and killed more than 170 people in Hawaii, a plan was devised to warn the public of possible tsunami inundation. The facility became operational in 1948 and was called the Seismic Sea Wave Warning System (SSWWS), headquartered at the Coast and Geodetic Survey's seismological observatory in Honolulu, Hawaii. Initially, the Seismic Sea Wave Warning System covered only the Hawaiian Islands and was limited to teletsunamis (distant events), using data from 4 seismic stations and 9 tide gages. The expanded system became operational in April 1965 but, like its local predecessor, was limited to teletsunamis – tsunamis which are capable of causing damage far away from their source. The system covered all countries of the Pacific Ocean with data from 20 seismic stations around the world and 40 tide stations. The 1975 Hawaii earthquake and tsunami, which killed several people, highlighted the threat of tsunamis caused by nearby events. As a result, PTWC began issuing tsunami warnings for local events near Hawaii. In October 2014, the authority to issue official tsunami warnings for coastlines in the Pacific was delegated to individual member states. This happened because warnings and watches issued by PTWC caused confusion when they conflicted with a country's independently derived level of alert. As a result, the center now issues advice rather than official warnings for all non-U.S. coastlines, with the exception of the British Virgin Islands. In 2015, the annual operating cost of the Pacific Tsunami Warning System was estimated to be between 50 and 80 million U.S. dollars. As of 2023, the Pacific Tsunami Warning System has access to about 600 high-quality seismic stations around the world and about 500 coastal and deep-ocean sea level stations. It has 46 member states: Brunei, Cambodia, Canada, Chile (including Easter Island and the Juan Fernández Islands), China (which is considered to include Hong Kong and Macau), Colombia, Costa Rica, East Timor, North Korea, Ecuador (including the Galapagos Islands), El Salvador, Guatemala, Honduras, Indonesia, Japan, Malaysia, Mexico, Nicaragua, Panama, Peru, Philippines, South Korea, Russia, Singapore, Thailand, United States (including Guam, Northern Mariana Islands, and the Minor Outlying Islands), Vietnam, Australia (including Norfolk Island), Cook Islands, Fiji, France (including French Polynesia, New Caledonia and Wallis and Futuna), Kiribati (including the Gilbert Islands, the Phoenix Islands and Kiritimati), the Marshall Islands (including Kwajalein Atoll and Majuro), the Federated States of Micronesia, Nauru, New Zealand (including the Kermadec Islands), Niue, Palau, Papua New Guinea, Samoa, the Solomon Islands, Tokelau, Tonga, Tuvalu, the United Kingdom (including the Pitcairn Islands), and Vanuatu. ==Coverage area==

Official tsunami warnings and watches are limited to U.S. coastlines, with the exception of the British Virgin Islands. PTWC messages for other regions do not include alerts, but rather advice, as the authority to issue tsunami warnings was delegated to member states in 2014 to avoid confusion among the public. and the UNESCO site. Email and text messages are also available from the USGS Earthquake Notification Service which includes tsunami alerts. ==Deep-ocean tsunami detection==

In 1995, 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. Beginning in 2005, as a result of the tsunami caused by the 2004 Indian Ocean earthquake, 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 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 Ocean. ==References==