Section IV. EFFECTS OF THE MAIN TSUNAMI AND OF 

 LOCAL SEISMIC SEA WAVES IN ALASKA 



1. Tsunami at Kodiak City, Kodiak 



We return to consider the effects of the tsunami on the coastal 

 communities of Alaska commencing with Kodiak in particular. We have seen 

 in Section III-2 that the Kodiak Island group was assailed by gigantic 

 waves of about 2.5 hours period (Figure 38c), whose first effect was 

 negative, according to location, and resulted in a relative withdrawal 

 of water in the initial stages of arrival. This withdrawal was not evi- 

 dent in some cases, particularly at Womens Bay, apparently because the 

 land sank, and with it the sea. The extent of this subsidence has been 

 given as 5.5 to 5.8 feet (Brown, 196U; Plafker and Kachadoorian, 1966; 

 Kachadoorian and Plafker, 196?; Bryant, I96I+ ) . The U. S. Coast and 

 Geodetic Survey and the U. S. Army Corps of Engineers have accepted 

 5.8 feet. 



The general topography of the region suggests that the direct path 

 of the tsunami toward Womens Bay and Kodiak would have been via Chiniak 

 Bay, with the wave front initially parallel to the hinge line of zero 

 vertical earth movement (Figures 87 and 88). In the absence of long- 

 wave refraction diagrams, it is difficult to determine exactly how such 

 long waves would have reached Kodiak City. We may infer, however, that 

 the deep channel running between Woody Island and Near Island (Figure 

 8Tb) would have favored the waves reaching Kodiak first from the northeast 

 via the channel between Near Island and Kodiak City. 



At Kodiak City, only about 5 nautical miles (in direct line) from 

 Kodiak Naval Station (about 10 nautical miles in terms of wave distance 

 via Womens Bay) (see Figure 87), there were conflicting opinions about 

 how the water behaved immediately after the earthquake (Chance, I968; 

 Plafker and Kachadoorian, I966 ; Kachadoorian and Plafker, I967). Many 

 claim that the first wave was a fast-rising tide noticeable at about 

 6:10 p.m., AST, or about 1/2 hour after the earthquake, which would 

 accord with what Lt . Barney had logged for Womens Bay (Figure 38). A 

 few have contended that the first wave came much earlier - within 10 

 minutes of the earthquake. The most convincing evidence for this early 

 wave comes from Jerry Tilley, a crewman on the shrimpboat Fortress^ which 

 was tied at the city dock, Kodiak (Figure 89). What happened, according 

 to Tilley, reproduced from Kachadoorian and Plafker (1967 ), follows : 



5:35 or 5:36 p.m. - Shock felt aboard boat. Boil of reeking black 

 water arose from beneath boat. 



5:U5 p.m. - Approximately 13-foot tide at dock when predicted tide 

 should have been +0.5 feet. (The 13-foot level is prequake 

 elevation above MLLW. Since land level dropped 5.5 to 5.8 

 feet postquake elevation above MLLW would be 7.2 to 7.5 feet.) 



5:50 p.m. - Cut loose from dock as water began to recede. 



137 



