J 



This wave ostensibly had a continuous front over a distance 

 of approximately 65O kilometers and propagated mainly north- 

 west and southeast. 



The inferred heights of the tsunami at or near the source 

 confirm an empirical-statistical result (Equation (6), 

 p. 62), based on Japanese data, which permits approximate 

 prediction of tsunami height near an earthquake source in 

 terras of earthquake magnitude . 



k. The tsunami propagated outward across the Pacific Ocean as 

 a fairly pure system of virtually non-dispersive, long 

 waves with a period averaging 1.8 hours. 



1. This period of the tsunami waves confirms an empirical- 

 statistical result (Equation (l9), p. lOH ) based on Pacific 

 Ocean data, which permits approximate prediction of primary 

 tsunami wave period for any given earthquake magnitude. 



m. The empirical results mentioned under items (g) and (l) 

 indicate that tsunami period T is directly proportional 

 to source region size (equivalent diameter S), a result 

 which is verified theoretically. 



n. The proportionality relationship bet'^reen T and S yields a 



value of T(= 1.99 hours) for the value of S(=U25 kilometers ! 

 in fair agreement with the average tsunami period (T = 1.8 

 hours) found in tide records. 



2. Tsunami Propagation Characteristics 



a. The tsunami appears to have propagated across the Pacific 

 as a system of modulated waves with five waves in the first 

 beat. The modulation shape was probably related to the 

 transverse profile shape of the vertical tectonic earth 

 movement . 



b. Changes in beat-modulation shape of the primary tsunami 

 waves result from interference of tsunami wave trains, 

 probably through "caustic" effects of wave refraction. 



c. On propagation of the tsunami waves over a continental or 

 insular shelf there appears to be immediate transfer of 

 energy to higher harmonics which seem restricted to the 

 odd harmonics . 



d. Particular coastlines, inlets, and bays of the Pacific 

 Ocean boundary are resonators for the primary and/or odd 

 harmonics of the tsunami waves and amplify the effects to 

 large proportions. 



374 



