From this 



d = _J i 000_ = 4 

 L 154,350 



and 



kd = 0.0194(2tv) = 0.122 

 Therefore, kd < 1.363 and the wave is stable. 

 ************************************* 



Galvin (1970) investigated waves propagating through water of uniform 

 depth in a laboratory wave tank. He found that the initial generated 

 waves broke down into several waves which are called solitons. Figure 24 

 illustrates an example where, for a water depth of 0.15 meter (0.5 foot) 

 and a generator period of 5.2 seconds, each of the initial waves broke 

 down into five solitons. Taking these waves as shallow-water waves, the 

 wavelength is approximately 6.4 meters, and kd '^ 0.15 which would indicate 

 that the waves are stable. However, it may be assumed that the generated 

 waves were not actually single waves, but rather a combination of several 

 solitons. Galvin noted that if a group of such waves traveled over a 

 sufficiently long distance, the solitons would recombine into single 

 waves, separate again into solitons, etc. There are commonly two or 

 thre'e solitons, but as many as seven could exist in some instances. If 

 a generated tsunami had the characteristics of a group of solitons, it 

 could appear differently at various coastal points, depending on the 

 distance from the generating area. 



Zabusky and Galvin (1971) compared numerical and experimental 

 results for solitons, using the Korteweg-deVries equations, for cases 

 where 22 < U < 777, where U is defined as (H/d)(L/d) 2 . They found 

 good comparisons for slightly dissipative waves. Hammack and Segur 

 (1974) also studied numerical and experimental results. They found that 

 soliton generation is dependent on the net volume change in the body of 

 water. When the net volume of the initial wave system was positive 

 (e.g., from uplifting of the sea bottom), solitons evolved followed by 

 a dispersive train of oscillatory waves. If the initial generating 

 mechanism was negative everywhere (sea bottom subsidence), no solitons 

 evolved. 



Byrne (1969) made field observations of waves passing over a near- 

 shore bar. He noted that a wave passing over a bar would sometimes 

 produce a second, trailing wave as shown schematically in Figure 25. 

 As these additional waves developed near the shoreline, he was unable 

 to determine if such waves would recombine with the waves in the initial 

 wave train. 



84 



