NOAA's two Tsunami Warning Centers (PTWC and WC/ATWC) have separate areas of responsibility, which are the geographical areas within which each Center has the responsibility for the dissemination of messages and the provision of interpretive information to emergency managers and other officials, news media, and the public.
As the primarly operational headquarters for the Pacific Tsunami Warning System, PTWC provides warnings for Pacific basin teletsunamis (tsunamis that can cause damage far away from their source) to almost every country around the Pacific rim and to most of the Pacific island states. This function is carried out under the auspices of the UNESCO/IOCInternational Coordination Group for the Pacific Tsunami Warning System. A few destructive teletsunamis are generated each century by great earthquakes around the Pacific rim. Such tsunamis can propagate across the entire Pacific in less than 24 hours, and cause widespread destruction along shorelines located thousands of miles from the source. With ever-increasing population and development along most coastlines, there is a corresponding increase in risk. The last destructive teletsunami occurred in 1964 following the great Alaska earthquake.
As a U.S. National Tsunami Warning Center, PTWC provides warnings for teletsunamis to Hawaiʻi, Guam, American Samoa, Wake Island, Johnston Island, the Commonwealth of the Northern Marianas, the Federated States of Micronesia, the Republic of the Marshall Islands, and all other U.S. interests in the Pacific located outside WC/ATWC's area of responsibility (Alaska, British Columbia, Washington, Oregon, and California). PTWC serves as a backup to WC/ATWC.
PTWC is the interim warning center to nations bordering the South China Sea (China, Macao, Hong Kong, Taiwan, Philippines, Malaysia, Brunei, Indonesia, Singapore, Thailand, Cambodia, Vietnam).
As the Hawaiʻi Regional Tsunami Warning Center, PTWC provides a more rapid warning for local tsunamis generated in Hawaiian waters. Two significant local tsunamis have been generated in Hawaiʻi in historical times, one in 1868 and one in 1975. Both were caused by major earthquakes that displaced the sea bottom along the southeast flank of the island of Hawaiʻi. Although these tsunamis caused damage and casualties only on that island, a future local tsunami could have adverse effects further up the island chain. Local tsunamis strike nearby shores almost immediately after being generated by the earthquake. Consequently, the earliest warning for a local tsunami is the strong shaking of the ground, and persons near the shoreline that feel strong shaking should evacuate immediately without waiting for an official warning.
PTWC is the interim warning center to countries in the Coastal Hazards Warning System for the Caribbean and Adjacent Regions (CARIBE).
From 2005-2007, PTWC was the interim warning center to U.S. Interests (Puerto Rico, Virgin Islands) in the Caribbean Sea. The WC/ATWC now provides this service to U.S. interets in the Caribbean.
From 2005-2013, PTWC provided an interim tsunami warning service to the Indian Ocean Tsunami Warning and Mitigation System (IOTWS). Service is now being provided by Regional Tsunami Service Providers in Australia, India, and Indonesia.
The WC/ATWC is the authoritative tsunami warning center for the western and eastern coasts of the United States mainland and Canada.