The Richard H. Hagemeyer Pacific Tsunami Warning Center (PTWC) serves as the international warning center for tsunamis that pose a Pacific-wide threat. This international warning effort became a formal arrangement in 1965 when PTWC assumed responsibility as the operational center for the Tsunami Warning System in the Pacific (TWSP).

The ICG/ITSU, a subsidiary body of the IOC comprised of 25 international Member States, oversees TWSP operations and facilitates coordination and cooperation in all other international tsunami mitigation activities.

   The initial objective of PTWC is to detect, locate and determine the seismic parameters of potentially tsunamigenic earthquakes occurring in the Pacific Basin or its immediate margins. To accomplish this, it continuously receives seismographic data from more than 150 stations around the Pacific through cooperative data exchanges with the U.S.

 Geological Survey, Incorporated Research Institutions for Seismology, International Deployment of Accelerometers, GEOSCOPE, the U.S. West Coast/Alaska Tsunami Warning Center (WC/ATWC), and other international agencies running seismographic stations and networks.
   If the earthquake location, depth, and magnitude criteria needed to generate a tsunami are met, a tsunami warning is issued to warn of an imminent tsunami hazard.

 Initial warnings apply only to areas the tsunami could reach within a few hours and bulletins include the predicted tsunami arrival times at selected coastal communities within those areas.

 Communities located outside those areas are put into either a tsunami watch or advisory status.
  Warning center scientists then monitor incoming sea level data to determine whether a tsunami has occurred. If a significant tsunami with long-range destructive potential is detected, the tsunami warning is extended to the entire Pacific Basin.

 PTWC receives sea level data from more than 100 stations through cooperative data exchanges with the U.S. National Ocean Service, WC/ATWC, the University of Hawaii Sea Level Center, Chile, Australia, Japan, Russia, and other international sources.

Tsunami warnings, watches, and information bulletins are disseminated to appropriate emergency officials and the general public by a variety of communication methods.
   In addition, individual countries may operate National or Regional Warning Centers to provide warning information on regional or local tsunami threats. The Japan Meteorological Agency provides tsunami warnings Japan, and additionally to Korea and Russia for events occurring in the Sea of Japan or East Sea.

The Centre Polynesien de Prevention des Tsunamis provides warnings in French Polynesia, and Chile (Sistema Nacional de Alarma de Maremotos) and Russia (Russian Hydrometeorological Service) operate national warning systems.
   In the United States, WC/ATWC provides tsunami warnings to the U.S. West Coast and Canada, and PTWC provides tsunami warnings to Hawaii and all other U.S. interests in the Pacific. Other countries, including Australia, Colombia, Nicaragua, Peru, and Korea, are also developing warning capabilities.