Weigel (1974) notes that management of the tsunami warning system 

 was transferred to the Environmental Research Laboratories, NOAA, in 

 1971, then to the National Weather Service in 1973. 



1 . The Tsunami Warning System . 



The Intergovernmental Oceanographic Commission (IOC) maintains an 

 International Coordination Group for the Tsunami Warning System in the 

 Pacific. Member countries are Canada, Chile, China, Ecuador, France, 

 Guatemala, Japan, Korea, New Zealand, Peru, Philippines, Thailand, 

 U.S.S.R., and the United States. The warning system is based on 51 

 tide stations and 32 seismograph stations (1976 IOC data) . The tsunami 

 warning system in the United States is based at the Honolulu Observatory 

 and receives data, from 18 seismograph stations and 16 tide states in the 

 United States (including Alaska and Hawaii, but excluding Pacific Ocean 

 territories), as well as the remaining 14 seismograph and 35 tide sta- 

 tions of the Tsunami Warning System in the Pacific (including Pacific 

 Ocean territories) . Tsunami warnings for the United States are based 

 primarily on the stations in the United States and on those stations 

 located in both North and South America. Stations in the Pacific Ocean 

 territories of the United States and those in the remainder of the 

 Pacific provide additional information on the tsunamis; but generally, 

 tsunamis that would create a hazard on the coastlines of the United 

 States do not arrive from those directions . 



The tsunami warning system functions best for distantly generated 

 tsunamis, i.e., tsunamis where the arrival time is several hours after 

 the initial wave generation. However, the warning system can also alert 

 the population to the possibility of tsunami generation from nearby 

 seismic activity. As the period of the tsunami varies from several min- 

 utes to approximately 30 to 40 minutes, continuously recording tide gages 

 are required. Modern, digital tide gages which provide a tide height 

 every several minutes will not provide sufficient data for recording 

 tsunamis . 



An alarm attached to the seismograph at Honolulu Observatory is 

 triggered by the arrival of seismic waves, initiating activity in the 

 Tsunami Warning System. The 1964 Alaska earthquake began at 0336 G.m.t. 

 (Spaeth and Berkman, 1972), and the alarm sounded at Honolulu Observatory 

 at 0344 G.m.t. (G.m.t. times are used to provide a uniform time at all 

 points in the system.) After the alarm, inquiries are sent to various 

 seismic observatories in the system to obtain seismic readings. After 

 receiving and evaluating initial data, a decision is made as to whether 

 or not an advisory bulletin should be issued. If there is a possibility 

 of tsunami generation, an advisory bulletin is sent to dissemination 

 agencies in the warning system. 



Charts showing tsunami traveltimes between various coastal points 

 and tsunami-generating areas have been prepared. These charts are 

 used to predict the arrival time of a potential tsunami at the various 

 coastal points after the epicenter of the earthquake has been determined. 



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