APPENDIX C 



TSUNAMI CHARACTERISTICS AND RUNUP - THEIR PREDICTION 

 RELATED TO THE ABILITY FOR DAMAGING STRUCTURES 



Alf T?$rum 



The damaging effect of tsunamis of the same wave height may vary 

 to a great extent. Isaacs (cf. Wiegel , 196k), in regard to the damage 

 at Oahu during the tsunami of April 1, 19^6, suggested the damage caused 

 by tsunamis may be roughly screened into the following three categories: 



1. Damage or effect of tsunami did not exceed that which would 

 be expected from an equal tidal inundation without surf. 

 Typical houses would be floated from their foundations or 

 merely flooded, but moved little; vegetation not disturbed 

 greatly. 



2. Damage or effect of tsunamis was intermediate between 1 and 3 

 conditions. Houses were moved some distance and damaged. 

 Ground was somewhat eroded. 



3. Damage or effect of the tsunami seemed disproportionately 

 great compared with that which would be expected from a 

 tidal inundation of similar height. Evidence of high 

 velocity everywhere. Buildings destroyed, reef coral 

 carried far inland, automobiles rolled about, escarpment 

 and stripping produced, and in level regions invasion of 

 the water for great distance inland. 



These same categories are also applicable to the tsunami of the 

 196k Alaskan earthquake. 



What determines the category of damage seems to be primarily whether 

 the waves break or not, and to what extent they break. A nonbreaking 

 wave will presumably cause mostly damage according to the first category, 

 light breaking waves cause damage according to the second, and the most 

 violent breaking wave causes damage according to the third category. 



It is not within the scope of this study to deal in detail with the 

 problem of nonbreaking and breaking of waves and the related problem of 

 runup. However, we would like to go into this question to the extent 

 it shows the deficit in the theory when trying to understand the behavior 

 of the tsunamis at different places. 



If a wave does not break, its energy is assumed to be completely 

 reflected when neglecting friction; while in fully breaking waves, the 

 wave energy is assumed to be completely transformed into heat by 



C-l 



