Table 3-5. Tidal Ranges 



Tsunamis cross the sea as very long waves of low amplitude. A wave- 

 length of 100 miles and an amplitude of 2 feet is not unreasonable. The 

 wave may be greatly amplified by shoaling, diffraction, convergence, and 

 resonance when it reaches land. Sea water has been carried higher than 

 35 feet above sea level in Hilo, Hawaii by tsunamis. Tide gage records 

 of the tsunami of 23-26 May 1960 at these locations are shown in Figure 

 3-38. The tsunami appears as a quasi-periodic oscillation, superimposed 

 on the normal tide. The characteristic period of the disturbance, as well 

 as the amplitude, is different at each of the three locations. It is 

 generally assumed that the recorded disturbance results from forced oscil- 

 lations of hydraulic basin systems, and that the periods of greatest re- 

 sponse are determined by basin geometry. 



3-74 



