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ANNUAL REPORT SMITHSONIAN INSTITUTION, 1947 



direction of wave advance, it should be somewhat less than twice the 

 wave height. This measure represents the height of dash of solid 

 water, but very abundant spray may be thrown much higher. More- 

 over, storm waves riding on the crest of the broader swells of the 

 tsunami undoubtedly added in places to the height to which water 

 dashed on shore. There are places where normal trade-wind waves 

 are flung to a height nearly as great as that reached by the tsunami, 

 and many places, particularly on shores facing away from the origin 



FiGTjBE 4. — Map of the island of Oahu, showing the heights reached by the water 

 during the tsunami of April 1, 1946. Heights are in feet above lower low 

 water. 



of the tsunami, where waves of heavy storms reached appreciably 

 higher than did the waves of the tsunami. 



It is not possible to make reliable estimates of the magnitudes of 

 these complicating factors, as there are too many unknown elements 

 involved. However, it is probable that most of the water heights 

 recorded for the tsunami on the northern and eastern sides of the 

 islands were appreciably increased by these factors. 



FACTORS INFLUENCING THE HEIGHTS AND INTENSITIES OF THE 



WAVES 



It may be assumed that the size and speed of the waves approaching 

 the islands from the open ocean to the north were essentially the same 

 throughout the length of the Hawaiian Archipelago. Differences in 



