Familiarize yourself with these terms to help identify a tsunami hazard:
When major earthquakes occuring in the Pacific Rim have magnitudes large enough to warrant concern..., NOAA's Pacific Tsunami Warning Center will notify authorities and others through advisory messages. These messages are information bulletins, warnings or watches. In any case the message will be posted at the PTWC Web site. The type of messages, will depend on the situation as interpreted initially from seismic data:
Tsunami Warning / Watch / Advisory Warnings issued by the National Weather Service's tsunami warning centers are alphanumeric products providing tsunami warning, watch and advisory warning information for potentially damaging tsunamis. The center?s operational objectives are to: a) locate and size major earthquakes in the Pacific basin, b) determine their tsunamigenic potential, c) predict tsunami wave arrival times and, when possible, run-up on the coast, and d) provide timely and effective tsunami information and warnings to the population of the Pacific to reduce the hazards of tsunamis, especially to human life.
These bulletins are prepared by each of two Tsunami Warning Centers. The West Coast/Alaska Tsunami Warning Center (WC/ATWC), located at Palmer, Alaska, issues tsunami bulletins to its Area of Responsibility (AOR) that is Alaska, British Columbia, Washington, Oregon, and California. It also has the primary responsibility for the detection, location, and magnitude determination of magnitude of potentially tsunamigenic earthquakes occurring in its AOR.. The Richard H. Hagemeyer Pacific Tsunami Warning Center (PTWC). The PTWC, located at Ewa Beach, Oahu, Hawaii, has the responsibility for issuing tsunami bulletins to its AOR that includes Hawaii, all other U.S. interests in the Pacific, and most other countries within the Pacific and around its rim. It has the primary responsibility for the detection, location, and magnitude determination of magnitudes for potentially tsunamigenic earthquakes occurring anywhere in the Pacific Basin outside the WC/ATWC AOR.
Pacific-wide Tsunami Warning
A Pacific-wide tsunami warning bulletin is issued by the PTWC after confirmation has been received that a tsunami has been generated in the Pacific that has caused damage, or has the potential to cause damage, at distances greater than 1000 kilometers from the epicenter, and thus poses a widespread threat to any populated coastal area within the Pacific Basin. Subsequent bulletins are issued at least hourly or as conditions warrant to reiterate the threat and to provide sea level gauge readings and other reports of tsunami wave activity. When significant wave activity has subsided, a warning cancellation is issued.
Regional Tsunami Warning
A regional tsunami warning bulletin is a tsunami warning issued initially to coastal areas near the earthquake epicenter. It is usually based only on seismic information without tsunami confirmation, and is initially issued as a means of providing the earliest possible alert of a potentially destructive tsunami to the population near the epicentral area of a potentially tsunamigenic earthquake. Areas in a regional tsunami warning are generally less than three hours from the estimated tsunami arrival time. A list of estimated arrival times for warning areas is provided in the bulletin. This condition implies that all coastal areas in the region should be prepared for imminent flooding. Subsequent bulletins are issued at least hourly or as conditions warrant to continue the warning, to expand or restrict the warning area, or to end the warning. A regional tsunami watch and advisory may also be issued in the same bulletin.
Urgent Local Tsunami Warning
An urgent local tsunami warning is a tsunami warning issued by the PTWC to Hawaii for tsunamis generated in Hawaiian coastal waters. It may be based only on seismic information without tsunami confirmation, or on a combination of seismic and sea level data, and is issued as a means of providing the earliest possible alert of a potentially destructive local tsunami. Areas in an urgent local tsunami warning may have only minutes or seconds before tsunami waves arrive, so urgent action is required to save lives. Subsequent bulletins are issued as conditions warrant to continue the warning, to expand or restrict the warning area, or to end the warning.
Final Warning Supplement
A final warning supplement bulletin is issued following a damaging or potentially damaging tsunami within a Centers' AOR that may pose a continuing threat. A final warning supplement bulletin provides guidance to local officials on when they can consider the threat to have passed based on their local tsunami conditions. The cancellation or all clear decision must be made locally.
A warning cancellation is issued as the final bulletin indicating when there is no longer the threat of a damaging tsunami to a Centers' AOR. A cancellation is usually issued after an evaluation of sea level data confirms that a destructive tsunami will not impact the AOR. It may also be issued following a destructive tsunami when data indicate that the threat has largely subsided to non-destructive levels. In that case, it provides guidance to local officials regarding when they can consider the threat to have passed based on their local tsunami conditions. The all clear decision must be made locally.
Regional Tsunami Watch
A regional tsunami watch is a tsunami watch issued in conjunction with a regional tsunami warning to coastal areas near the earthquake epicenter, but outside the warning area. It is usually based only on seismic information without tsunami confirmation, and is issued as a means of providing the earliest possible alert of a potentially destructive tsunami. Areas in a regional tsunami watch are generally less than six hours from the estimated tsunami arrival time, and a list of estimated arrival times for watch areas is provided in the bulletin. Subsequent bulletins are issued at least hourly or as conditions warrant to continue the warning and watch, to expand or restrict the warning and watch areas, to upgrade the watch to a warning, or to end the warning and watch. A regional tsunami warning and advisory may also be issued in the same bulletin. The bulletin, usually based only on seismic information without tsunami confirmation, is issued as a means of alerting the population within 1 to 3 hours travel time beyond the tsunami warning area of an earthquake with the potential to have generated a tsunami that may affect that area. Subsequent bulletins are issued at least hourly or as conditions warrant to expand the watch area, upgrade it to a warning, or end the watch and warning. A Regional Tsunami Watch may be included in the text of the message that disseminates a Regional Tsunami Warning.
Tsunami Advisory Bulletin
A tsunami advisory bulletin is issued to areas not currently in either warning or watch status when a tsunami warning has been issued for another region of the Pacific. An Advisory indicates that an area is either outside the current warning and watch regions or that the tsunami poses no danger to that area. The Center(s) issuing the Advisory will continue to monitor the event, issuing updates at least hourly. As conditions warrant, the Advisory will either be continued, upgraded to a watch or warning, or ended.
Tsunami Information Bulletin
A tsunami information bulletin is issued for informational purposes for events that will not cause a destructive tsunami but were large enough in size to have been detected by the tsunami warning center?s seismic monitoring networks. Some of these earthquakes may have been large enough, however, to cause earthquake-related damage.
Source: Peter Pissierssens (http://www.tsunamiwave.info)