242 Long Waves in Canals and Standing Waves in Closed Basins 



Lagrange wave velocity. With this V equation (VI. 151) takes the form 



J_ 



dx 



T = T\At- 



(VI. 152) 



in which At = t — t . The two latter values can be computed numerically, 

 when the bottom profile along the path of travel is given. One particular 

 form of the solution (VI. 152) is T = l/a(At — J/T 2 ), where a is an arbitrary 

 constant. In this case one has a cubic equation in T. The simplest solution is 

 found by setting a = 0, and T— [/[//(*— f«)]. 



The application of these theoretical computations to the tsunami of 

 1, April 1946, gave a qualitatively good agreement between the theory and 

 observations. Theoretically the wave period must increase with distance of 

 travel, but decreases with time at each station, as the observations actually 

 show. The observed periods seem to be somewhat shorter in the northern 

 Pacific Ocean and somewhat longer in Valparaiso than those computed by 

 the theory. However, in view of the incorrectness in the determination of 

 the periods from marigraphs, one can be satisfied with the quantitative 

 results. 



In the development of the "tidal" wave on a shore the configuration of 

 the coast plays a great part. The waves approaching the coasts from the free 

 ocean initiate eigen-oscillations of the bays (seiches) and of parts of the 

 shelf which add to the wave disturbances and confuse in this way the basic 



Fig. 102. Area inundated by Tsunami of 3 March 1933 in Bay of Sasu. (Numbers 

 indicate the height of the flood in meters.) 



