278 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1947 



It appears inevitable that future tsunamis will cause loss of property 

 on Hawaiian shores, but loss of life from all except tsunamis of local 

 origin could be largely or entirely avoided. A system of stations 

 could be established around the shores of the Pacific and on mid- 

 Pacific islands, which would observe either visually or instrumentally 

 the arrival of large long waves of the periods characterizing tsunamis. 

 The arrival of these waves should be reported immediately to a central 

 station, whose duty it would be to correlate the reports and issue warn- 

 ings to places in the path of the waves. It should be possible in this 

 way to give the people of the Hawaiian Islands enough warning of the 

 approach of a tsunami to permit them to reach places of safety. The 

 effectiveness of the warning, however, would depend on education of 

 the public on the necessity for leaving areas of danger, and on the 

 efficiency of the local organization in spreading the warning and evacu- 

 ating the threatened areas. Eventually it should also be possible to 

 state, at the same time, which areas are likely to suffer the most damage. 

 Before that can be done, however, we need more knowledge of the 

 behavior of tsunamis on Hawaiian shores, particularly tsunamis from 

 sources in the eastern and western Pacific, and a more complete picture 

 of the submarine topography around the Hawaiian Islands. 



SUMMARY 



The tsunami which reached the shores of the Hawaiian Islands on 

 April 1, 194G, was the most destructive in the history of the Islands. 

 Generated by a sudden shifting of the sea bottom on the northern 

 slope of the Aleutian trough, the waves traveled southward to Hawaii 

 with an average speed of 490 miles an hour, an average wave length 

 of about 122 miles, and a height over the deep ocean of about 2 feet. 

 Effects on Hawaiian shores varied greatly. Locally the water dashed 

 more than 50 feet above sea level and swept as much as half a mile 

 inland. Elsewhere the rise in water level was very small, and waves 

 were gentle. Property damage was heavy but loss of life was moderate. 



The heights and intensities of the waves at different points were in- 

 fluenced by position on the island toward or away from the source 

 of the waves, offshore submarine topography, presence or absence of 

 coral reefs, shore-line configuration, mutual reinforcement or inter- 

 ference by waves traveling different paths, and the presence or absence 

 of storm waves. Loss of property during future tsunamis can be 

 reduced by proper construction, by erection of sea walls, and by re- 

 stricting or prohibiting construction in certain especially dangerous 

 areas. Loss of life can be nearly or entirely eliminated by the estab- 

 lishment of a suitable system for warning of the approach of waves. 



