SENAT
Report n° 117 (2007-2008) by M. Roland COURTEAU, Senator (for the parliament office for the evaluation of scientific and technological choices) - Appendix to the minutes of the 7 December 2007 session
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2. ... that relies on effective national systems
The three national systems here presented constitute the most successful warning systems to date. While they may not be perfect, they endeavour to meet the three preconditions for setting up an effective warning system: 1) an operational warning centre, 2) a pre-defined, emergency action plan that has been pre-tested on the ground, and 3) a population informed and made aware of the threat.
a) The American model
(1) Two warning centres
The Hawaiian centre has already been discussed above; however, it is necessary to emphasize the fact that this centre has retained its original warning mission for the United States. Indeed, the US National Tsunami Warning Center issues tsunami warning bulletins for Hawaii, Guam, American Samoa, Wake Island, Johnston Island, the Northern Mariana Islands and all other American interests in the Pacific not covered by the Alaskan warning centre.
What's more, as the regional tsunami warning centre for Hawaii, PTWC rapidly issues warning bulletins in the event of a local tsunami generated in the Hawaiian waters.
According to the information gathered by your rapporteur, there are 70 seismic stations located in Hawaii. PTWC requires 10 seconds to detect an earthquake, 15 seconds more for its localization, and 1.5 minute to determine its magnitude. However, considering the very short time lapse between the generation of a tsunami and its arrival on the coasts (10 minutes for the local tsunami of 29 November 1975), teaching the concerned population the right reflexes remains the most effective protective measure: when someone along the coast feels the ground shake, he/she must immediately seek higher ground, without waiting for an official warning.
In addition to PTWC, the United States created a second warning centre for Alaska in 1967, following the teletsunami of 27 March 1964 which originated in this region. 14 ( * )
In 1982, the geographical zone for which the centre issues its warning bulletins was extended to the states of California, Oregon, Washington and British Colombia, in the event of a tsunami-generating earthquake occurring in their coastal zones.
In 1996, the Alaskan centre once again had its mission extended, for it is now in charge of warning the four previously mentioned states in the event of a tsunami originating anywhere in the Pacific.
Following the devastating Sumatra tsunami of 26 December 2004, the WC/ATWC could also issue tsunami warnings to the Atlantic coast of the United States, as well as the Gulf of Mexico region, Puerto Rico, the Virgin Islands and the Atlantic coast of Canada.
Therefore, the United States has two tsunami warning centres which ensure the protection of its coasts and can replace one another if need be (should one centre encounter technical difficulties which prevent it from functioning correctly, or should several tsunamis originate in different areas at the same time).
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Tsunamis on the American coasts: local or transoceanic tsunamis? The zones most at risk of local and transoceanic tsunamis are the Hawaiian islands and the Pacific coasts of California, Oregon and Washington. Alaska and the Caribbean islands (Puerto Rico and the Virgin Islands) are, for the most part, threatened by local tsunamis. |
* 14 The West Coast/Alaska Tsunami Warning Center (WC/ATWC).