I 



Homer suffered mainly from the regional subsidence (2 to 3 feet), 

 ifferential compaction, and lateral spreading (l to i| feet) (Waller, 

 966; Gronewald and Duncan, I965). Wave damage, confined to inundation, 

 as slight. Figure 131 shows the general effect of the subsidence on 

 he Spit. 



At Seldovia, the earth motion appears to have been predominantly 

 ast-west (Berg, et al, 196^+; Chance, 1968), Numerous waves were re- 

 orted by different eyewitnesses which suggest that waves 12 to 15 feet 

 bove tide level, of a period of about 2 minutes, developed during the 

 arthquake, but did no damage because their reach was below high tide 

 evel (Chance, 1968). Other waves, after the earthquake, appear to have 

 ccurred at intervals of 15 minutes and U5 minutes . The surges of 3 to 

 feet high at intervals of 15 minutes could very well be related to 

 ransverse oscillations of the water body across Seldovia Bay (Figure 

 32), which may be likened to a semi-quartic basin (Wilson, 1966) of 

 0,000 feet length and 35 feet maximum depth (at Seldovia). Such a 

 asin would have first and second mode oscillations of about 25 and 12.5 

 inutes, respectively. Without extended analysis of the whole bay, the 

 5 minute period waves are unexplained. 



Strong tides were observed to occur at 7=00 (Berg, et al, I96U), at 

 i:00 and 9:00 p.m. (Chance, 1968). The tide at 9:00 p.m. may have reached 

 lose to normal high tide level for the area. On its recession at about 

 1:10 p.m. this wave carried away some boat floats (Chance, 1968). This 

 s presumed to be the same wave that reached Homer at 11:30 p.m. 



A second major wave is presumed to have arrived at about 11:10 to 

 1:30 p.m. and again at about 2:00 a.m. March 28, on the high astronomical 

 dde (Berg, et al, 196U). The tsunami elevation above normal tide level 

 t this time was estimated by Berg, et al, to be about h feet. 



Wave damage at Seldovia, mostly by inundation, was relatively slight, 

 lome boat floats were lost, and the breakwater suffered some damage from 

 ompaction due to the earth tremors and from waves (see Eckel, I96T). 



Halibut Cove (a wide bay almost due east of the end of Homer Spit, 

 'igure 130) also reported a wave of 2U feet at 11:35 p.m. (Waller, I966) 

 'hich could have been the same one that hit Seldovia at 11:10 p.m. If 

 -hese waves were tsunamis coming in from the Gulf of Alaska, Homer was 

 >robably also hit by these waves although no high waves had been reported 

 t Homer at that time. The reason could be simply that nobody was at the 

 'aterfront to report any waves. 



We have remarked that the tsunami would encounter a strong refractive 

 Jid diffractive effect on entering Cook Inlet. The exact effect of this 

 s difficult to assess, but it seems realistic to assume a diffraction 

 oefficient of approximately O.U at Seldovia and Homer, which could explain 

 'hy the tsunamis were not more seriously felt at these places. 



203 



