Table 7. Typology of tsunami events (after Haas, 1978) 



Tsunami 

 type 



Physical 

 clues 



Approximate time 

 for evacuation 



Maximum credible 

 preventive action 



I 



Visible 

 slumping 

 or sliding 



Less than 1 

 minute 



Almost none 



II 



Severe 



Earth 



temblors 



5 to 10 minutes 



Ambulatory persons 

 can be evacuated 



III 



Noticeable 



Earth 



shocks 



15 to 30 minutes 



Some persons can be 

 evacuated 



IV 



None 



45 minutes to 

 12 hours 



Most persons can be 

 evacuated and up to 

 75 percent of all 

 movable property 



Haas notes that while no effective warning can be given for a type 

 I tsunami, the possibility of warnings for types II, III, and IV will 

 depend on the education of the public and the effectiveness of warning 

 systems. Evacuation for a type II tsunami requires prompt response by 

 the population based on their individual sensing of strong earthquake 

 shocks, and little time is available for an organized warning system to 

 operate. Therefore, there is almost total reliance on prior education. 



For a type III tsunami, public education alone is insufficient because 

 the physical evidence of a possible tsunami is not as strong. A reliable 

 local warning system is needed to alert the public, and the population 

 must be educated to respond to the alert. For a type IV tsunami, a large 

 warning system, such as the Tsunami Warning System in the Pacific, is 

 required. 



Weller (1972) cites a number of instances of human response during 

 the 1964 earthquake and tsunami in Alaska. At Seward, the initial slump- 

 ing of the waterfront gave warning to the residents of the town, and most 

 people evacuated the low areas; but 11 people were killed by a wave 9 to 

 12 meters (30 to 40 feet) in height. At the village of Kaguyak on Kodiak 

 Island, residents moved to high ground when they observed the initial 

 signs of a tsunami; but three people were killed when they returned to 

 low areas before the arrival of the largest wave. At Ouzinkie, on Spruce 

 Island, the residents evacuated the town when they observed the initial 

 development of wave action offshore, and there was no loss of life. 



Many lives are lost either because some residents do not respond to 

 visible signs of a possible tsunami, such as at Seward, or residents 



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