258 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1947 



who furnished descriptions of the wave effects on Niihau and Lanai, 

 respectively; the Hawaii County engineer's office, which supplied a 

 map showing the extent of flooding in Hilo; and the United States 

 Coast and Geodetic Survey, which supplied data on the earthquake 

 and the record of the Honolulu tide gage, and permitted the use, in 

 advance of publication, of C. K. Green's manuscript on the tsunami 

 along the shores of North and South America, Howard A. Powers, 

 seismologist of the Volcano Observatory at Hawaii National Park, 

 aided greatly in the investigation on the island of Hawaii. Miss 

 Maude Jones, archivist of the Territory of Hawaii, and Miss Margaret 

 Titcomb, librarian of the Bishop Museum, aided in locating records 

 of past waves. C. K. Wentworth and H. S. Palmer aided greatly 

 in discussions. Wentworth and Walter Munk read and criticized the 

 manuscript. J. Y. Nitta prepared the illustrations. 



DEFINITION OF "TSUNAMI" 



The name "tsunami" - is applied to a long-period gravity wave 

 in the ocean caused by a sudden large displacement of the sea bottom 

 or shores. A tsunami is accompanied by a severe earthquake, but 

 the earthquake does not cause the tsunami. Rather, both are caused 

 by the same sudden crustal displacement. The waves of a tsunami 

 have a period of several minutes to an hour as contrasted with sev- 

 eral seconds for ordinary storm waves caused by wind, a wave length 

 of scores of miles as contrasted with less than 500 feet for wind waves, 

 and a speed of hundreds of miles an hour as contrasted with less than 

 60 miles an hour for wind waves. Tsunamis are also sometimes termed 

 "seismic sea waves," and are popularly known as "tidal waves." The 

 latter term is patently undesirable, as the waves have no connection 

 whatever with the tides. "Tsunami" is used herein in preference to 

 "seismic sea wave" because of its greater brevity, and because the 

 etymological correctness of the term "seismic sea wave" appears open 

 to question.^ 



HISTORY OF TSUNAMIS IN HAWAII 



Tsunamis probably reach Hawaiian shores on an average of more 

 than one a year. Most of these are small, however, and generally 

 escape notice except when their record is recognized on tide gages. 

 Earlier tsunamis in Hawaii have been discussed by Jaggar (1931) 



' Also spelled "tunami," the Japanese equivalent of the letter "t" being pronounced 

 "ts" in English. It appears preferable, however, to use the phonetic spelling in English, 

 avoiding thereby much Incorrect pronunciation. 



' The adjective "seismic" is derived from the Greek root seismos, meaning earthquake, 

 and Is defined as pertaining to, produced by, or characteristic of an earthquake. The 

 waves in question are not, however, cliaracteristic of most earthquakes, even those of 

 submarine origin, and are not produced by earthquakes. 



