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PACIFIC SCIENCE, Vol. XXI, July 1967 
Fig. 1 . Generating area of the Alaska tsunami. Crossbatched area indicates ( — ) area of subsidence and 
( + ) area of uplift. Heavy dashed lines indicate the backward-refracted wave fronts. Solid line marked by a 
zero is the axis of rotation (no elevation change). Other solid lines indicate tectonic axes. 
runs east along the upper part of the sound. 
The line roughly parallels the Aleutian Trench 
axis and separates the Kodiak geosyncline from 
the shelf geanticline. 
The areas north and west of this line have 
undergone negative elevation changes, whereas 
the east and south underwent positive changes. 
An extensive pattern of positive surface dis- 
locations under the sea is suspected to lie east 
of the island of Kodiak and along the conti- 
nental shelf bordering the Gulf of Alaska. 
The extent of these dislocations still needs to 
be confirmed by detailed bathymetric surveys 
of the area, although large positive displace- 
ments have been observed as far south as 
Middleton Island and southwest to Sitkinak 
Island. Wave refraction studies, described 
here, also strongly indicated that the tsunami- 
generating area was mainly in the belt of uplift 
and included a large segment of the conti- 
nental shelf and slope. 
The zone between the known areas of tec- 
tonic uplift closely corresponds to a major 
crustal fault defined by crustal seismic mea- 
surements conducted by the Department of 
Terrestrial Magnetism of the Carnegie Insti- 
tution of Washington (Woollard et al., I960). 
In view of the shallowness of the earthquake 
(20 km), it was concluded that the crustal 
dislocations occurred alongside a zone of tilt- 
ing or a surface rupture (Grantz et al., 1964), 
but a survey of the area failed to identify such 
a feature. The focal depth corresponds, how- 
ever, to the base of the granitic layer defined 
by Woollard’s analysis of the crustal measure- 
ments made by the Carnegie Institution. 
The total area of tectonic displacements asso- 
ciated with the Alaska earthquake of March 
27, 1964 is estimated to be approximately 
215,000 km 2 . This is the largest area known 
to be associated with a single earthquake within 
historic time. 
The magnitude of the Alaska earthquake 
was estimated to be from 8.4 to 8.75, which 
