Since 1978, in-depth discussions have been carried out by the International Coordination Group for the Tsunami Warning System in the Pacific (the ICG/ITSU, now renamed the ICG/PTWS) on the establishment of regional tsunami warning centers to issue tsunami advisories tailored to particular regions in the Pacific. With regard to the Northwest Pacific region, the Republic of Korea proposed at the 14th session of the ICG/ITSU (Tokyo, 1993) that a center could be assumed by the Japan Meteorological Agency (JMA). This triggered an ICG/ITSU feasibility study to set up the regional center for the Northwest Pacific.
At the 17th ICG/ITSU session (Seoul, 1999), based on a survey of the regional requirements and state-of-the-art technology in predicting tsunami wave amplitude, JMA submitted a proposal to the session to establish a regional tsunami warning center for the Northwest Pacific at JMA, and the proposal was accepted by the session. After concentrated efforts in research and development to fully meet the requirements of the center, JMA submitted a report at the 19th ICG/ITSU session (Wellington, 2003) to demonstrate its readiness for the operation of the center. At its 37th session (Paris, 2004), the Executive Council of the Intergovernmental Oceanographic Commission (IOC) adopted a resolution to implement the services of the regional center at JMA by March 2005.
On such an international consensus, JMA initiated operation of the regional Tsunami Forecast Center at its headquarters in March 2005 to provide tsunami advisories to countries in the Northwest Pacific. At the 20th ICG/ITSU session (Vina del Mar, October 2005), the Agency reported the establishment of the Northwest Pacific Tsunami Advisory Center (NWPTAC), and those present at the session expressed their appreciation to Japan for undertaking the responsibilities of the organization. At the same session, the Group asked JMA to provide an interim tsunami advisory service for the South China Sea region. Accordingly, JMA upgraded its system and started the service as requested in April 2006.
ADVISORY SERVICE STATUS
The provision of Northwest Pacific Tsunami Advisory Center (NWPTAC) service is aimed at allowing recipient countries to take timely and appropriate action against tsunami threats in conjunction with tsunami bulletins from the Pacific Tsunami Warning Center (PTWC). It should be noted, however, that NWPTAs are simply advisories to be considered by recipients in alerting the people, and that the issuance of actual evacuation notices is the responsibility of each recipient. The accuracy of the estimated amplitude and arrival time of tsunamis in NWPTAs, as well as the time taken for forecast operation, are dependent on the availability of seismic data and technologies for hypocenter determination and quantitative tsunami forecasting. It is therefore highly advisable for recipient countries to make the best use of NWPTAs based on a full understanding of the technological background conditions as described below and in the annexes of the Users Guide.
NWPTAC makes every effort to disseminate NWPTAs as quickly as possible. However, people need to be alerted in advance of advisory receipt if a strong earthquake occurs in a coastal area, as tsunamis may form and reach the coast rapidly.
NWPTAs do not refer to the cancellation of warnings in subsequent issues because NWPTAC itself does not issue warnings. The Center holds the view that warnings should be officially issued and cancelled by the authorities of the countries concerned under their own responsibility because tsunami conditions vary with each nation's coastal terrain.
If there is a significant difference in the evaluation of tsunami severity between a PTWC bulletin and an NWPTA, the more severe version should be given priority.
Although the operational system for JMA's NWPTA service is duplicated in case of partial system malfunction, the possibility of a major system failure cannot be ruled out. If an NWPTA is not issued due to such unforeseen circumstances, the recipient countries/organizations of NWPTAs should take appropriate action in line with bulletins from PTWC.