A Study of the Source Mechanism of the Alaska Earthquake and 
Tsunami of March 27, 1964 
Part I. Water Waves 1 
George Pararas-Carayannis 
ABSTRACT: The geologic history and the general geomorphology of the area 
affected by the March 27, 1964 Alaska earthquake are given. The tsunami-generat- 
ing area is determined and the extent of crustal displacement and the limits of the 
areas of subsidence and uplift, as revealed by geologic evidence, are discussed. The 
dimensions of this tsunami-generating area, its volume of crustal displacement, 
and the energy associated with the tsunami are calculated. Wave activity within 
and outside the generating area and the possible generating mechanisms for the 
tsunami are discussed. A wave refraction diagram of the Alaska tsunami for the 
north Pacific Ocean area is presented in 
The Aleutian Island Arc and the Aleutian 
Trench extend for 2800 km from Kamchatka 
to south-central Alaska along remarkably smooth 
curves which are convex toward the south (Fig. 
1). The Arc forms the Alaska Peninsula and, 
according to Wilson (1954), intersects, north 
of Cook Inlet, a second tectonic arc that ex- 
tends northward from the vicinity of the 
Wrangell Mountains. However, Plafker (1965) 
regards this second segment as a continuation 
of the Aleutian Arc. Where the trench im- 
pinges on Alaska it loses its identity, although 
an offshore range of seamounts suggests it may 
once have extended around to the south to 
parallel the continental slope, as postulated by 
Menard and Dietz (1951). Concavity in the 
former shape of the trench on its eastern seg- 
ment is also suggested by the sedimentary arc 
defined by Wilson (1954), which embraces 
Kodiak Island and the Kenai Peninsula. As 
shown by Wilson, such concavity is to be ex- 
pected where two arcs meet at an acute angle, 
as is well exemplified where the Aleutian and 
Kuril-Kamchatka arcs intersect. It is also quite 
possible that large horizontal movements of 
crustal blocks have helped to change the shape 
of the Trench and Arc on their eastern seg- 
ments. However, no such evidence was found 
in a field study following the Good Friday 
earthquake (Berg et ak, in preparation). 
1 Hawaii Institute of Geophysics Contribution No. 
184. Manuscript received June 22, 1966. 
Figure 6. 
The nature of the termination of the eastern 
segment of the Aleutian Trench is obscured 
by thick sediments washed in from the conti- 
nental shelf against which it abuts offshore 
from Cape Suckling. The sediments are of geo- 
synclinal-dimensions in the sedimentary arc 
on Kodiak Island (Menard and Dietz, 1951) 
and as shown by drilling on the Kenai Penin- 
sula. Woollard et al. (I960) show there is 
geophysical evidence for at least 7 km of sedi- 
ments in Cook Inlet, a graben separating the 
primary arc from the offshore sedimentary arc. 
Sediment is about 2 km thick off Kodiak Island 
along the Aleutian Trench, thinning out to 
about 0.7 km south of Unimak Island in the 
deep water area, according to seismic measure- 
ments by Shor (1962). 
THE GENERATING AREA OF THE ALASKA 
TSUNAMI 
According to Van Dorn (1964), the tectonic 
dislocations associated with the Alaska earth- 
quake of March 27, 1964 ranged over a dis- 
tance of 800 km, from the upper portion of 
Prince William Sound to southwest of the 
Trinity Islands. The dislocations follow a di- 
pole pattern of positive and negative displace- 
ments on either side of a zero-line which, 
intersecting the east coast of Kodiak Island, 
continues northeast to the western side of Prince 
William Sound. There, changing direction, it 
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