TSUNAMIS 



G. F. Carrier 



Harvard University 

 Cambridge^ Massaohusetti 



I. INTRODUCTION 



An understanding of the coastal inundation caused by Tsunamis 

 requires the piecing together of several studies. Among the poten- 

 tially important characterizing features of the phenomenon are: the 

 temporal and spatial distribution of the ground motion which initiates 

 the Tsunam,i, the distance from the source to the target area in ques- 

 tion, the bottom topography of the intervening ocean, and the topag- 

 raphy of the coastal area itself. These are all discussed in some 

 detail in [ i] , a nnanuscript which was prepared in conjunction with 

 a longer series of lectures than this one. In order to avoid excessive 

 duplication of publication, we content ourselves here with a brief 

 summary of that material. As will be evident, many details remain 

 to be explored; unfortunately, there is no evidence to suggest that 

 even a miore comprehensive understanding of the phenomena will sug- 

 gest procedures for alleviating the intensity of Tsunami inundation. 



II. INITIATION AND DEEP WATER PROPAGATION 



The wave generated by a submarine earthquake is large 

 enough in lateral extent and small enough in amplitude so that a 

 linear theory is completely adequate for an analysis of the propaga- 

 tion over deep water. However, the propagation path is so long that 

 dispersion and its attendant changes in wave shape cannot be ignored. 

 Accordingly one can adopt either the classical linear theory of 

 gravity waves or the Boussinesque formalism to study the early 

 stages of the wave propagation. When either is done, for a basin of 

 constant depth, H, it is convenient to present the results in terms 

 of a particular family of initicd ground motions. We discuss here 

 the waves which result when the ground motion is given by 



Fo(x,t) = (irL^r'^^xp [- xV] 6(t). 



When the half width, L, of the distrubed region is "small," the 

 wave which arrives at a distance Xg will have been greatly affected 

 by dispersion; when the width of the generating ground motion is 



