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The operational objective of the TWS in the Pacific is to detect and locate major earthquakes in the Pacific region, to determine whether they have generated tsunamis, and to provide timely and effective tsunami information and warnings to the population of the Pacific to minimize the hazards of tsunamis, especially to human life and welfare. To achieve this objective, the TWS continuously monitors the seismic activity and ocean surface level of the Pacific Basin.
The TWS is an international program requiring the participation of many seismic, tide, communication, and dissemination facilities operated by most of the nations bordering the Pacific Ocean. Administratively, participating nations are organized under the IOC as the International Coordination Group (ICG) for the TWS in the Pacific (ICG/ITSU). The ITIC was established upon request of IOC and serves many roles in assisting ICG/ITSU member nations in mitigating the effects of tsunamis throughout the Pacific. The PTWC serves as the operational center for the TWS of the Pacific. PTWC collects and evaluates data provided by participating countries, and issues appropriate bulletins to both participants and other nations, states or dependencies within or bordering the Pacific Ocean basin regarding the occurrence of a major earthquake and possible or confirmed tsunami generation.
Functioning of the System begins with the detection, by any participating seismic observatory, of an earthquake of sufficient size to trigger an alarm attached to the seismograph at that station. Personnel at the station immediately interpret their seismograms and send their readings to PTWC. Upon receipt of a report from one of the participating seismic observatories or as a consequence of the triggering of their own seismic alarm, PTWC personnel will (1) check the Internet for email from the National Earthquake Information Center (NEIC) regarding the event. If the automatic picker at NEIC has not yet sent an email report, PTWC geophysicists will log onto the NEIC system and use data from their National Seismic Network (NSN) to locate the earthquake. The alarm thresholds at PTWC are set so that ground displacements of the amplitude and duration associated with an earthquake of approximate magnitude 6.5 or greater anywhere in the Pacific region will activate them. This magnitude is below the threshold for issuing Warning/Watch and is the threshold for issuing Information Bulletins.
After the earthquake has been located and magnitude determined, a decision is made concerning further action. If the earthquake is within or near the Pacific Ocean basin and its magnitude is 6.5 or greater, but less than or equal to 7.5 (less than or equal to 7.0 in the Aleutian Islands), then a Tsunami Information Bulletin is issued to the Warning System participants. Tsunami Warning/Watch Bulletins are issued to the dissemination agencies for earthquakes of magnitude greater than 7.5 (greater than 7.0 in the Aleutian Island region), alerting them to the possibility that a tsunami has been generated and providing data that can be relayed to the public so that necessary preliminary precautions can be taken.
If the earthquake appears to be strong enough to cause a tsunami and is located in an area where tsunami generation is possible, PTWC will check water level data from automatic tide stations located near the epicenter for evidence of a tsunami. If they show that a tsunami has been generated that poses a threat to the population in part or all of the Pacific, the Tsunami Warning/Watch Bulletin is extended until there is no longer the threat of a destructive tsunami or it is upgraded to a Warning for the whole Pacific. The dissemination agencies then implement predetermined plans to evacuate people from endangered areas. If the tide station data indicate that either a negligible tsunami or no tsunami has been generated, PTWC issues a cancellation of its previously disseminated Tsunami Warning/Watch.
In some areas of the Pacific Basin national or regional tsunami warning systems function to provide timely and effective tsunami information and warnings to affected populations. For those coastal areas nearest the tsunami source region, the need for rapid data handling and communication becomes obvious. Because of the time spent in collecting seismic and tide data, the warnings issued by PTWC cannot protect all areas in the Pacific against tsunamis generated in adjacent waters. To provide some measure of protection within the first hour after generation for tsunamis in the local area, national and regional warning systems have been established by some countries. Among the most sophisticated of the national systems are those of France (French Polynesia), Japan, Russia, Chile and the U.S.A. Regional systems provide the earliest possible alert to the population within the immediate vicinity of the earthquake epicenter by issuing immediate warnings based on earthquake information without waiting for tsunami wave confirmation.
A Regional (or Local) Tsunami Warning Center is responsible for the detection of tsunamis originating within the regional area of responsibility, the prediction of their arrival time within the region and, if possible, coastal impact, and the provision of the earliest possible information and warnings to those national interests responsible for the life and safety of the population of those coastal areas nearest the tsunami source. To function effectively, these regional systems generally have data from a number of seismic and tide stations telemetered to a central headquarters. Nearby earthquakes are located, usually in 15 minutes or less, and a warning based on seismic evidence is released to the population of the area. Since the warning is issued on the basis of seismic data alone, one may anticipate that warnings occasionally will be issued when tsunamis have not been generated. Since the warnings are issued only to a restricted area and confirmation of the existence or nonexistence of a tsunami is obtained rapidly, disruptions are minimized while a higher level of protection is obtained.
To ensure the timely and effective operation of the TWS, communication facilities are essential which are capable of rapidly handling the data requests from PTWC, the seismic and tide reports to PTWC, and Tsunami Warning/Watch and Information Bulletins. Since such traffic is relatively infrequent, existing communication channels are used with some supplementation where absolutely necessary, instead of establishing a separate communication system that would, to a large extent, duplicate existing channels. Hence, the communication channels under the management and control of the United States Defense Information Systems Agency (DISA), Federal Aviation Administration (FAA), National Weather Service (NWS), Army, Navy, Air Force, Coast Guard, various international agencies, and private companies are be used to handle the message traffic involved between PTWC and the seismic and tide stations and dissemination agencies participating in the warning system.
PTWC maintains the following communications services:
AUTODIN U.S. Department of Defense and State Department facilities
AFTN U.S. Federal Aviation Administration and International affiliates
NMC National Weather Service forecast and data subscribers
NWW National Weather Service subscribers and U.S. emergency service agencies
HCD State of Hawai`i Civil Defense and NWS offices
TELEX Emergency service agencies in some South America and Pacific island states
INTERNET Most international and domestic government agencies and academic institutions
FAX All the above
NAWAS Emergency management agencies nationwide
HAWAS Emergency management agencies in State of Hawaii
To disseminate Tsunami messages to U.S. Department of Defense activities throughout the Pacific Basin, PTWC maintains an AUTODIN GateGuard teminal from which messages are uploaded directly to the Multilevel Messaging System (MMS) at NCTAMS EASTPAC in Wahiawa, Hawai`i. USCINCPAC maintains a collective address header (RUCRTWP) that contains the AUTODIN addresses of some 192 separate commands and agencies requiring Tsunami message products. As an alternative method of delivery of messages into the AUTODIN system PTWC can request the NMC operator to relay tsunami products via its AUTODIN terminal to Fort Detrick Maryland. Once there, the products will be disseminated with exactly the same distribution as if transmitted directly from the PTWC.
The Aeronautical Fixed Telecommunications Network (AFTN) is a world-wide system of circuits for the exchange of messages and/or digital data beween stations primarily for the safety of air navigation and for the regular, efficient and economical operation of air services. Since most flight service facilities must be cognizant of current weather forecasts, many weather forecast offices are provided with AFTN terminals.
The acronym "NMC" in the NWS can have two interpretations: the National Meteorological Center, in Washington D.C. or the NOAA Message Center in Silver Spring Maryland. The circuit referred to as the NMC circuit at the PTWC is a 300 baud dedicated ASCII serial communication line between PTWC in Ewa Beach, Hawai`i and the Honolulu Weather Service Forcast Office. From there the line is multiplexed onto a high speed dedicated service to the NMC in Silver Spring Maryland.
The NMC circuit is used as a PTWC's means of sending Tsunami Bulletins into the World Meteorological Organization's (WMO) Global Telecommunications System (GTS) and into the domestic NWS AFOS system. The primary audience for messages sent on NMC are meteorological agencies. Messages are transmitted with WMO headers. All WMO headers describe a weather broadcast product category. The NMC in Silver Spring MD maintains a database (the Switching Directory) that directs these products to the appropriate subscribers' circuits automatically. This is also the means by which PTWC receives all the tide data from the automatic water level staions throughout the Pacific Basin. Some meteorological agencies that operate and maintain seismic networks within their country submit seismic phase pick information to PTWC by the GTS.
The NOAA Weather Wire is a satellite broadcast service maintained by the NWS to disseminate weather products domestically. Both the Alaska Tsunami Warning Center and PTWC have uplink and downlink capability on the NWW system. Users of the NWW system are comprised of Weather Service Offices and emergency management agencies. Receiver sites can program their selector box to receive any number of selected NWS products (or messages).
The Hawai`i State Civil Defense maintains a telecommunications network that connects all the Weather Service Offices, State and County Civil Defense offices in the State of Hawai`i. Messages transmitted on this circuit are copied simultaneously at all the connected office terminals.
A commercial Telex service (MCI) is maintained. The primary audience for Telex messages are remote stations or dissemination agencies that do not have access to the other services available at PTWC.
PTWC is connected to the Internet by a high speed direct link. The Internet is used for: (1) day-to-day business using e-mail services over the net, and (2) direct computer link with the National Earthquake Information Center and other seismic observatories.
The National Warning System is a nationwide dedicated voice telephone system connecting selected national defense, emergency management, and Coast Guard agencies. The circuit is supported by the Federal Emergency Management Agency (FEMA). Control over transmissions on the circuit is maintained by the National Warning Center located in Berryville, Virginia.
The Hawai`i Warning System is a statewide dedicated voice telephone system connecting selected State Civil Defense, National Guard, Law Enforcement and Weather Service Offices. The circuit is supported by the FEMA and Hawai`i State Civil Defense. Control over transmissions on the circuit is maintained by the State Warning Point.
The PTWC issues four basic types of information, as summarized below:
A. Pacific-wide Tsunami Warning Bulletin - A message issued to all participants on a Pacific-wide basis after confirmation has been received that a tsunami capable of causing destruction beyond the local area has been generated and poses a threat to the coastal population for the entire Pacific Basin. Each hour updated information will be sent until the Pacific-wide Tsunami Warning is canceled.
B. Regional Tsunami Warning/Watch Bulletin - A message issued initially using only seismic information to alert all participants of the probability of a tsunami and advise that a tsunami investigation is underway. The area placed in Tsunami Warning status will encompass a 3-hour tsunami travel-time relative to the time of message issuance . Those areas within a 3 to 6-hour tsunami travel-time will be placed in a Watch status. A Tsunami Warning/Watch will be followed hourly by additional bulletins until it is either upgraded to a Pacific-wide Tsunami Warning or is canceled.
C. Tsunami Information Bulletin - A message issued to advise participants of the occurrence of a major earthquake in the Pacific or near-Pacific area, with the evaluation that either (a) A Pacific-wide tsunami was not generated based on earthquake and historical tsunami data. This will be the only bulletin issued. No Pacific-wide tsunami warning is in effect; or (b) An investigation is underway to determine if a Pacific-wide tsunami has been generated. Additional bulletins will be issued hourly or sooner as information becomes available. No Pacific-wide tsunami warning is in effect; or (c) No destructive Pacific-wide tsunami threat exists. However, some areas may experience small sea level changes. This will be the final bulletin issued unless additional information becomes available. No Pacific-wide tsunami warning is in effect.
If the event occurs in ATWC's area of responsibility and exceeds the ATWC Regional Warning threshold but is less than the PTWC Warning/Watch threshold an investigation will be initiated by PTWC and additional Tsunami Information Bulletins will be issued until the investigation is concluded.
D. Tsunami Communication Test - Test messages are issued by PTWC at unannounced times on a monthly basis to determine writer-to-reader delays in disseminating tsunami information, to test the operation of the warning system by the evaluation of two-way communications with interactive personnel response, and to keep communication operating personnel familiar with the procedures for handling message traffic pertaining to the TWS .
A summary outline of the operational procedures used by PTWC for the issuance of the above bulletins as related to earthquake magnitude on the Richter scale (Ms) is as follows:
EARTHQUAKE MAGNITUDE
*PTWC ACTION
A. Mwp greater than Alarm threshold. but less than 6.5
*Provide data and information to USGS/NEIC and/or other participating observatories
B. Mwp equal to or greater than 6.5. but less than or equal to 7.5 (7.0 in the Aleutian Islands)
*Issue TSUNAMI INFORMATION BULLETIN, with the evaluation that a Pacific wide tsunami was not generated.
C. For events in ATWC's area of responsibility exceeding ATWC Warning threshold, but less than PTWC Warning/Watch threshold.
*(1) Monitor pertinent tide stations.
*(2) Issue TSUNAMI INFORMATION BULLETIN with initiation of Investigation.
*(3) Based on tide station response:
*(a) Issue final TSUNAMI INFORMATION BULLETIN
*(b) Issue TSUNAMI WARNING.
*(c) Continue investigation by issuing additional TSUNAMI INFORMATION BULLETIN.
D. Mwp greater than 7.5 (or 7.0 for Alaska)
*(1) Issue REGIONAL TSUNAMI WARNING/WATCH BULLETIN. Issue E/Q ADVISORY or WATCH for State of Hawaii (see note below).
*(2) Monitor pertinent tide stations.
*(3) Based on tide station response:
*(a) Issue CANCELLATION of REGIONAL TSUNAMI WARNING/WATCH BULLETIN.
*(b) Issue PACIFIC-WIDE TSUNAMI WARNING BULLETIN.
*(c) Continue investigation by issuing additional REGIONAL TSUNAMI WARNING/WATCH BULLETINS until the tsunami warning/watch is canceled.
(4) On issuance of a PACIFIC-WIDE TSUNAMI WARNING, continue investigation by issuing TSUNAMI WARNING BULLETINS until the tsunami warning/watch is canceled.
Note: For the Hawaii Civil Defense only, a separate message text consisting of an EARTHQUAKE ADVISORY is issued for Mwp greater than 7.5 and ETA for Hawai`i greater than 6 hours. A WATCH is issued for Mwp greater than 7.5 (7.0 for Alaska) and ETA less than 6 hours. Hawai`i also is included in WATCH status for earthquakes from Tokyo to Kamchatka. A WARNING is issued upon tsunami confirmation.
When a major tsunami is detected, a Tsunami Warning Bulletin will be sent out to all participants in the Pacific. A Pacific-wide Tsunami Warning is transmitted on AUTODIN circuits with FLASH precedence, on AFOS with priority 1, and on AFTN circuits with SS priority. Pacific-wide Tsunami Warnings are issued by PTWC upon receipt of positive evidence that a potentially destructive tsunami exists. Pacific-wide Tsunami Warnings will contain estimated times of tsunami arrival (ETA) at tide stations and specific warning points in the warning system. Pacific-wide Tsunami Warning Bulletins normally will carry information on wave heights and other information as deemed appropriate by PTWC.
The Pacific-wide Tsunami Warning will be canceled when it is determined that the tsunami threat is over for the entire Pacific Basin. A cancellation will be issued if the Tsunami Warning was issued on the basis of erroneous data or if PTWC determines from subsequent information that only an insignificant wave has been generated. In addition, a Pacific-wide Tsunami Warning may be canceled on a selective basis when a significant wave that has been generated clearly poses no threat to one or more of the areas PTWC warns, either because of intervening continents or islands which screen them or because the orientation of the generating area causes the tsunami to be directed away from these areas.
At present, PTWC does not have enough data available to enable it to determine when danger has passed in many areas. Local conditions can cause wide variations in tsunami wave action. Consequently, all-clear determinations must be made by the local action agencies and not PTWC. In general, after receipt of a Tsunami Warning, action agencies can assume all-clear status when their area is free from damaging waves for 2 hours unless additional ETA's have been announced by PTWC or local conditions, particularly strong currents in channels and harbors, warrant continuation of the Tsunami Warning status. If no wave or only insignificant waves occur, action agencies may assume all-clear status 2 hours after the latest ETA announced by PTWC, again taking caution as to the presence of strong currents in channels and harbors.
A Regional Tsunami Warning/Watch Bulletin will be issued to all participants in the Pacific informing them of the occurrence of a major earthquake which could generate a potentially destructive tsunami for the Pacific community. A Regional Tsunami Warning/Watch Bulletin is transmitted to the same addressees and with the same precedence and priority as a Pacific-wide Tsunami Warning, i.e., FLASH precedence on AUTODIN circuits with priority 1 on AFOS, and with SS priority on AFTN circuits.
A Regional Tsunami Warning/Watch is issued based on earthquake location and magnitude, generally exceeding 7.5 moment magnitude (7.0 for the Aleutians). The area within 3 hours tsunami travel-time of the epicenter will be placed in a Tsunami Warning status, with the area within a 3-6 hour travel-time zone placed in a Watch status. Tsunami ETA's will be disseminated for the tide stations within the Tsunami Warning and Watch areas. Action agencies so designated should evaluate the probability of a tsunami having been generated and decide on appropriate action. It must be emphasized that a Tsunami Warning/Watch is issued by PTWC based on earthquake information only, without confirmation of wave activity. Meanwhile, PTWC will have initiated an investigation by sending queries to the nearest tide stations.
Bulletins subsequent to the first Tsunami Warning/Watch Bulletin will be issued on an hourly basis. This policy will be adhered to even when no new data are available. Additional bulletins will be issued until the Tsunami Warning/Watch is upgraded to a Tsunami Warning, or until PTWC determines that no tsunami was generated, at which time the Tsunami Warning/Watch will be canceled. If a small tsunami is detected, PTWC may extend the Tsunami Warning/Watch status until certain that no danger exists to further areas.
Note: For Alaska, British Columbia, Washington, Oregon and California. PTWC in its role as the international operational center for the TWS in the Pacific is the responsible warning center to all ICG/ITSU nations for tsunamis originating anywhere in the Pacific. PTWC in its role as the U.S. National Tsunami Warning Center is the responsible warning center to all U.S. national interests for tsunamis originating anywhere in the Pacific. The Alaska Tsunami Warning Center (ATWC) functions as the Regional Tsunami Warning Center for Alaska and for the west coast of North America for tsunamis generated from Attu, Alaska to the southern California border. For tsunamis generated in the region from Attu to the southern California border PTWC Regional Tsunami Warning/Watch Bulletins will include a statement that the ATWC has issued a Regional Tsunami Warning. This is to minimize possible confusion for those dissemination agencies receiving both a Regional Tsunami WARNING/WATCH from PTWC and a Regional Tsunami WARNING from ATWC. Because ATWC is the Regional Tsunami Warning Center and as such should have the most specific and timely information, its message should be acted upon first by agencies in those areas.
When a major earthquake occurs in a coastal or near-coastal location, or within the Pacific basin, with a moment magnitude from 6.5 to 7.5 (7.0 for the Aleutians) on the P-wave, PTWC will issue a Tsunami Information Bulletin, with the evaluation that a Pacific-wide tsunami was not generated. If PTWC's evaluation is such that tsunami generation is possible, the nearest tide stations will be monitored. A Tsunami Information Bulletin is transmitted on AUTODIN circuits with IMMEDIATE precedence, on AFOS with priority 1, and on AFTN circuits with SS priority. If ATWC issues a Regional Tsunami Warning for an event that is less than PTWC's Warning/Watch threshold, a Tsunami Information Bulletin will be issued by PTWC advising that an investigation is underway, and acknowledging that ATWC has issued a Regional Warning/Watch for (area).
On initiation of a tsunami investigation, additional bulletins will be issued hourly until the investigation is canceled, or positive information is received that a potentially destructive tsunami has been generated, at which time a Regional Warning/Watch or Pacific-wide Warning will be issued.
Tsunami Communication Test messages are sent at unannounced time on a monthly basis to various selected dissemination agencies to test the operation of the warning system, to keep communication operating personnel familiar with the procedures for handling message traffic pertaining to the system, and to determine transmission times.
Tsunami Communication Test messages from PTWC to dissemination agencies are transmitted via SS priority for AFTN circuits, priority 1 for AFOS, and FLASH precedence for AUTODIN circuits to evaluate the effectiveness communications during a real event. Responses from dissemination agencies may use a routine priority or Precedence for test messages.
The text of test messages, and ONLY test messages, will begin with the words "TSUNAMI COMMUNICATION TEST " to distinguish these messages from other action bulletins transmitted by PTWC.
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