be balanced against the high cost of casualties to the local population 

 if a tsunami occurs without sufficient warning. 



Cox and Stewart (1972) discuss the particular problems of providing 

 tsunami warnings to areas near a tsunami source. Tsunami warnings must 

 be timely to be effective. To reduce the hazards on particular coast- 

 lines, a policy of regional evaluation was adopted in 1966. Adams (1978) 

 discusses the local tsunami warning system used in Hawaii. Seismic 

 detection instruments have been placed in police and fire stations and 

 similar locations. Seismic activity with a magnitude which may generate 

 a tsunami triggers an alarm. A decision is then made at the local level 

 as to whether or not the local population should be alerted and evacuated. 



Various investigators have called attention to phenomena occurring 

 just before a tsunami. These include the unusual feeding habits of 

 fish before a tsunami due to the presence of large quantities of bottom- 

 adherent diatoms in the upper layer of the sea (Suyehiro, 1934) and 

 increases in the Earth's magnetic field preceding an earthquake (Moore, 

 1972). The study of such phenomena has not been developed enough to be 

 included in a formal tsunami warning system. 



2. Human Response . 



Spaeth and Berkman (1972) note that the response of a local population 

 to a tsunami warning may be slow unless the population is well trained to 

 respond. Approximately 30 minutes after the Alaska earthquake of 1964, 

 the U.S. Fleet Weather Central at Kodiak Naval Station received word of 

 a large tsunami at Cape Chiniak, Alaska, and had the Armed Forces Radio 

 Station broadcast a tsunami warning. Military and government personnel 

 promptly evacuated the endangered areas. Although reasonably prompt, 

 the evacuation of the city of Kodiak was not as well carried out (there 

 were eight deaths at Kodiak) . The first large tsunami wave crest arrived 

 at Kodiak about 30 minutes after the warning, so a prompt response to the 

 warning was essential. 



Haas (1978) separates tsunamis into the following four types (summa- 

 rized in Table 7) : 



(a) Type I. Shoreline slumping, earthslides, and large rock 

 and ice falls coincident with the earthquake. Large waves gener- 

 ated onto the shoreline almost immediately. 



(b) Type II. Very heavy Earth temblors can be felt by the 

 local population for a period up to several minutes. The tsunami 

 arrives within 10 minutes. 



(c) Type III. Noticeable Earth shocks felt by the local popu- 

 lation for a period up to several minutes. Severe Earth temblors 

 not present. Tsunami arrives within 30 minutes. 



(d) Type IV. No local Earth shocks. The tsunami is generated 

 at a distant source. 



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