The Alaska Earthquake 

March 27, 1964 

Regional Effects 

Ground Breakage in 

the Cook Inlet Area 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 543-F 

THE ALASKA EARTHQUAKE, MARCH 27, 1964: 

REGIONAL EFFECTS 

Ground Breakage and 

Associated Effects in the 

Cook Inlet Area, Alaska, 

Resulting from the 

March 27, 1964, Earthquake 

By HELEN L. FOSTER and THOR N. V. KARLSTROM 

A description of the ground cracks ,and 

deposits from ground-water eruptions 

and crustal changes, particularly in the 

Kenai Lowland 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 543-F 
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEW ART L. UDALL, Secretary 

GEOLOGICAL SURVEY 

William T. Pecora, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1967 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 
THE 

ALASKA EARTHQUAKE 

SERIES 

The U.S. Geological Survey is publishing theresults of investigations of the earthquake in a series 

of six Professional Papers. Professional Paper 543 

describes the regional effects of the earthquake. 

Other Professional Papers describe the history of 

the field investigations and reconstruction effort; the 

effects of the earthquake on communities; the effects 

on hydrology; and the effects on transportation, 

communications, and utilities. 

CONTENTS 

Page Page Page 

Abstract_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ F 1 Ground breakage-Con. Causes of ground breakage_ _ _ _ _ F24 

Introduction__________________ 1 Kenai Lowland______________ F3 Crustal changes in the Cook InScope of report and source of Northeast-trending zone____ 3 let region_________________ 25 

data_____________________ 1 Coasts_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 12 Observed coastal changes_____ 25 

Acknowledgments___________ 2 Large lakes_______________ 14 Tilting of lake basins________ 26 

Regional geologic setting_____ 2 Southern interior__________ 17 Pattern of subsidence________ 27 

Geologic history and local geo- Northern Cook Inlet area_ _ _ _ 19 Conclusions___________________ 28 

logic setting______________ 2 Northwest side of Cook Inlet_ 23 References______________ _ _ _ _ _ _ 28 

Ground breakage______________ 3 Southeast side of Kachemak 

Types of breakage___ _ _ _ _ _ _ _ _ 3 Bay______________________ 24 

ILLUSTRATIONS 

PLATES 

[Plates are in pocket] 

1. Map showing ground breakage reSJUlting from the 1964 Alaska earthquake in the Kenai Lowland. 

2. Map of Cook Inlet area. 3. Map of dis:ruption on outwash delta of Tustumena Lake. 

1. Index map ________________ _ 

2. Azimuth-frequency diagram 

showing dominant trend of 

ground cracks in the Kenai 

Lowland ________________ _ 

3, 4. Sketch maps of ground 

cracks in Kenai Lowland _________________ _ 

5-17. Photographs: 

5. Tree split by ground 

crack __________ _ 

6. Typical large ground 

crack in Kenai 

Lowland ________ _ 

7. Vertical displacement __________ _ 

8. Sand ridges deposited along ground 

crack __________ _ 

9. Large fissure ______ _ 

10. Large ground crack 

with vertical displacement ______ _ 

11. Microrelief features 

formed in extruded silt ______ _ 

Page 

VI 

F4 

5,6 

7 

8 

9 

9 

10 

10 

11 

FIGURES 

5-17. Photographs-Continued 

12. Small vent which 

extruded watery silt ____________ _ 

13. Detrital coal extruded with sand_ 

14. Ground cracks at 

Kasilof _________ _ 

15. Collapse pits at 

Kasilof _________ _ 

16. Outwash delta at 

head of Tustumena Lake a few 

days after the 

earthquake _____ _ 

17. Crack between delta 

front and bedrock 

at Tustumena 

Lake __________ _ 

18. Diagramshowingtypeof ground 

disruption on the north shore 

of Tustumena Lake _____ _ 

19. Diagram showing a type of 

slumping on south shore 

of Tustumena Lake _____ _ 

20. Sketch map of Eklutna valley ____________________ _ 

Page 

Fll 

13 

13 

14 

15 

15 

16 

17 

18 

21-23. Photographs of Eklutna 

valley: 

21. Sites of avalanche 

activity ___ - ___ _ 

22. Dust cloud ______ _ 

23. A crack in gravel 

outwash _______ _ 

24. Photograph of failure of the 

delta front at Troublesome 

Creek, Lake George ____ - -

25. Sketch map of Lake George area ___________________ _ 

26-27. Photographs of Lake 

George: 

26. Wall of silt punched up on the 

emerged bottom_ 

27. Silt squeezed up 

along cracks in 

the emerged bottom sediments __ 

28. Photograph of postearthquake high-tide mark along 

Turnagain Arm sea bluffs near Hope _____________ _ 

v 

Page 

F19 

19 

20 

21 

21 

22 

22 

25 
6Qo 

164° 160° 156° 152° 

~~ 

-11\' 

Active volcano 

Fault 

-=-}...--+-_.:..--~Dashed where approximate 

148° 

---/5000----

Submarine contour, in feet 

144° 

1.-Index map showing location of Cook Inlet area. 

140° 
THE ALASKA EARTHQUAKE, MARCH 27, 1964: REGIONAL EFFECTS 

GROUND BREAKAGE AND ASSOCIAT:ED EFFECTS IN THE COOK 

INLET AREA, ALASKA, RESULTING FR.OM THE 

MARCH 27, 1964, EARTHQUAKE 

By Helen L. Foster and Thor N. V. Karl strom 

The great 1964 Alaska earthquake 

caused considerable ground breakage 

in the Cook Inlet area of south-central 

Alaska. The breakage occurred largely 

in thick deposits of unconsolidated sediments. The most important types of 

ground breakage were ( 1) fracturing 

or cracking and the extrusion of sand 

and gravel with ground water along 

fractures in various types of landforms, 

and (2) slumping and lateral extension 

of unconfined faces, particularly along 

delta fronts. 

The principal concentration of 

ground breakage within the area covered by this report was in a northeasttrending zone about 60 miles long and 

6 miles wide in the northern part of the 

Kenai Lowland. The zone cut across 

diverse topography and stratigraphy. 

The great 1964 Alaska earthquake oaused considerable ground 

breakage in the Cook Inlet area of 

south -central Alaska. Cook Inlet 

is the major marine reentrant of 

the Gulf of Alaska; it extends inland between the Kenai and Chugach Mountains and the Alaska 

Range (fig. 1). It is bordered by 

extensive lowlands on the east, 

northwest, and north. The epicenter of the earthquake (fig. 1) was 

to the east and northeast of Cook 

Inlet and separated from it by 

ABSTRACT 

Cracks were as much as 30 feet across 

and 25 feet deep. Sand, gravel, and 

pieces of coal and lignite were extruded 

along many fissures. It is suggested that 

the disruption in this zone may be due 

to movement along a fault in the underlying Tertiary rocks. 

The outwash deltas of Tustumena 

and Skilak Lakes in the Kenai Lowland, of Eklutna Lake and Lake George 

in the Chugach Mountains, of Bradley 

Lake in the Kenai Mountains, and at 

the outlet of upper Beluga Lake at the 

base of the Alaska Range showed much 

slumping, as did the delta of the 

Susitna River. Parts of the flood plains 

of the Skilak River, Fox River, and 

Eagle River were extensively cracked. 

A few avalanches and slumps occurred along the coast of Cook Inlet in 

INTROD1UCTION 

part of the Chugach Mountains 

~and the Kenai Mountains. The 

greatest ground breakage outside 

of the Anohorage and Portage 

areas was in the Kenai Lowland, 

about 115 air miles west of the 

epicenter. 

SCOPE OF REPORT AND 

SOURCE OF DATA 

This report is concerned primarily with the ground breakage 

and related phenomena in the lowland areas of Cook Inlet-parscattered localities. Some tidal flats 

were cracked. However, in view of the 

many thick sections of unconsolidated 

sediments and the abundance of steep 

slopes, the cracking was perhaps less 

than might have been expected. 

Observations along the coasts indicated changes in sea level which, although caused partly by compaction of 

unconsolidated sediments, may largely 

be attributed to crus1tal deformation accompanying the earthquake. Most of 

the Cook Inlet area was downwarped, 

although the northwest side of Cook 

Inlet may have been slightly unwarped. 

Maximum change in the Cook Inlet area 

was probably less than 6 feet. Little or 

no regional tilting was detected in the 

lake basins of Tustumena and Skilak 

Lakes. 

ticularly the more populated and 

accessible Kenai Lowland. Descriptions of the damage in the 

Anchorage and Portage areas are 

available in previously published 

reports (Grantz and others, 1964; 

Hansen, 1965). Some observations 

of ground breakage in the northwestern part of the Chugach 

Mountains are included here. 

Most of the information on 

earthquake effects presented in 

this report is based on field observations made by K a r 1 s t r o m 

F1 
F2 

between May 10 and July 15, 1964, 

and by Foster from May 10 to the 

end of May. Ground observations 

were made in the parts of the 

I\.:enai Low land accessible by road 

and along beaches. I\.:ar lstrom 

made boat traverses along the 

shores of Tustumena Lake, Skilak 

Lake, and Lake George. The 

ground observations were supplemented by reconnaissance from 

fixed-wing planes and by the study 

of aerial photographs made after 

the earthquake by the U.S. Army, 

the U.S. Coast and Geodetic Survey, and the U.S. Geological Survey. Localities near the head of 

Cook Inlet were checked primarily 

by road traverses. On the west side 

of Cook Inlet only one ground 

traverse was made near Tyonek. 

Other observations there were 

from fixed-wing planes. 

Ground breakage is difficult to 

detect from the air, especially in 

wooded areas. Consequently, some 

localities with ground breakage 

undoubtedly have been overlooked, 

particularly west of Cook Inlet. 

ACKNOWLEDGMENTS 

Special acknowledg1nent is due 

Mr. David M. Spencer, Mr. Robert 

Ward, Mr. Avery Thayer, and Mr. 

Will Troyer of the U.S. Fish and 

Wildlife Service in Kena.i, Alaska, 

who provided essential logistic 

support and supplied personal observations on changes in areas not 

visited by U.S. Geological Survey 

personnel. Thanks are also due Mr. 

Joe Magargl and Mr. George 

Calvin of Kasilof for their assistance during the boat traverse 

around the shores of Tustumena 

Lake, and to numerous members 

of the U.S. Geological Survey sta.-

tioned in Anchorge and Palmer, 

who supplied critical information 

based on personal observations of 

the earthquake effects. George 

Plafker, David McCulloch, Roger 

Waller, and Reuben I\.:achadoorALASKA EARTHQUAKE, MARCH 2·7, 1964 

ian, all of the U.S. Geological Survey, made their unpublished data 

available and gave assistance during the preparation of the manuscript. 

REGIONAL GEOLOGIC 

SETTING 

The Cook Inlet area is near the 

juncture of the western Pacific 

island arc system and the orogenic 

belts of the western part of North 

America. Just northeast of Cook 

Inlet the trends of the mountain 

ranges abruptly change from 

northwest to southwest and extend 

in broad subparallel arcs (fig. 1). 

Near the apices of these arcs the 

granite-cored Talkeetna Mountains separate the Chugach Mountains from the Alaska Range and 

form the divide between the head 

of Cook Inlet and the in termontane Copper River basin to the 

east. Several arcuate fault zones 

have been 1napped in central and 

southern Alaska; these in part follow and in part transect the mountain-·range structures. One of the 

faults, the Lake Clark-Castle 

Mountains fault, cuts the Alaska 

Range just north of Cook Inlet 

(Dutro, 1957), there having a 

northeasterly trend. A belt of high 

seismicity, coincident with the 

a pi cal zone of the arcuate mountain structures, extends from 

Prince William Sound beyond 

Fairbanks north of the Alaska 

Range and includes the epicenter 

of the main shock of the 1964 

earthquake. 

GEOLOGIC HISTORY AND 

LOCAL GEOLOGIC SETTING 

The geologic structure of the 

Cook Inlet area is highly complex. 

The rocks of the region record a 

history of repeated geosynclinal 

sedimentation, deformation, and 

intrusion beginning in Paleozoic 

time and extending through the 

Tertiary. Near the end of the 

Cretaceous, there was downwarping and subsidence of the Cook 

Inlet trough and, in the Tertiary, 

rocks that are now locally more 

than 15,000 feet thick were deposited. By the end of Tertiary 

time, the major topographic elements of the area were established. 

The subsequent geologic history 

has consisted largely of erosion 

and modification of the mountainous areas during repeated glacialinterglacial cycles ·and of pa~tia;} 

filling of lowland area.s and valleys 

with glacial drift and associated 

deposits (l{arlstrom, 1964). Offsets of surficial deposits, along preexisting faults in bedrock, indicate 

continuing sporadic tectonism in 

the region through the Quaternary and to the present. In the 

Cook Inlet area, it was primarily 

the thick m1consolidated deposits 

of Quaternary age that locally 

failed by fissuring, slumping, and 

subsidence during the 1964 Alaska 

earthquake. 

The Kenai Lowland part of the 

Cook Inlet area had the most 

ground breakage and therefore 

was examined in more detail; it is 

a broad low shelf 20 to 50 miles 

wide and 106 miles long. Most of 

the low land is less than 400 feet 

above sea level, surfaces are flat to 

undulating, and local relief varies 

from a few feet to more than 200 

feet. The Caribou Hills, a broad 

glaciated upland north of Homer, 

rise abruptly 1,000 to 2,000 feet 

above the general low land surface. 

Remnants of this same upland surface occur as piedmont slopes 

adjacent to the Kenai Mountains 

between Skilak and Tustumena 

Lakes (I{arlstrom, 1964, p. 12). 

Drainage in the Kenai Low land 

is poorly integrated, and numerous lakes, marshes, and muskeg 

areas make up 1nore than a third 

of the total surface. Two major 

lakes, Tustumena and Skilak, 
GROUND BREAKAGE:, COOK INiLIET AREA, AL.A:S'KA F3 

occupy glacially scoured and moraine-dammed troughs and are 

drained respectively by the Kasilof 

and Kenai Rivers, which empty 

into Cook Inlet. Along the shoreline of l{enai Lowland are wavecut cliffs that range in height from 

800 feet in the Kachemak Bay area 

to less than 50 feet near the mouths 

of 1najor drainage lines (Karlstrom, 1964, p. 12) . Tertiary bedrock is exposed locally beneath glacial deposits in the cliffs, especially 

along the northwest shore of 

TYPES OF BREAKAGE 

Ground failures in the Cook Inlet area include most of the types 

that occurred elsewhere during the 

1964 earthquake and that are described in detail from adjoining 

regions in other chapters of the 

U.S. Geological Survey 1964 

Alaska earthquake series. Types of 

failure include ( 1) rock falls and 

avalanches resulting from dislodgement of bedrock, colluvium, 

and snow on steep rocky slopes; 

( 2) landslides on moderate to 

gentle slopes with downslope migration of surface materials giving 

rise to tensional cracking and folding (pressure ridges) ; (3) slumping and lateral extension of surficial deposHs toward steep unconfined faces (river banks, lake 

shores, delta fronts, and sea bluffs) 

that cause tensional and rotational 

fracture patterns; ( 4) transverse 

and longitudinal tensional cracking of surface gravel in va.Iley flood 

plains and valley trains ; and ( 5) 

concentric and transverse cracking 

of frozen surface layers of muskeg 

and elevated tidal flats resulting 

largely from differential compac262-870 0-67-2 

Kachemak Bay and along the 

Cook Inlet shoreline south of 

Kasilof. 

A complex of Quaternary moraines and associated drift and outwash deposits of several ages covers the greater part of the Kenai 

Lowland (pl. 1). Locally, the deposits are more than 400 feet thick. 

The moraines have been modified 

to different degrees by erosion, by 

an irregular cover of loess, and by 

mantling with proglaciallake sediments. Other proglacial lake sediGROUND BREAKAGE 

tion and downslope movements of 

underlying water-saturated finegrained deposits. 

There was also extensive ground 

breakage and extrusion of sand 

and gravel along fractures which 

cut across the topography and so 

seem, at least in part, unrelated 

to it. 

KENAI LOWLAND 

NORTHEAST-TRENDING ZONE 

Most localities of major ground 

breakage in the Kenai Low land 

are roughly alined northeastsouthwest in a zone 60 miles long 

and 6 miles wide which extends 

from Kasilof on the east shore of 

Cook Inlet to Chickaloon Bay on 

the south sho.re of Turnagain Arm 

(pis. 1, 2). 

The zone of ground breakage 

crosses an area of diverse landforms underlain by Quaternary 

surficial deposits of differing 

origin and age (Karlstrom, 1964). 

Included are elevated tidal flats of 

Recent age, end moraines of l{nik 

( preclassical Wisconsin) age near 

Kasilof and Chickaloon Bay, and 

an interlobate moraine of Eklutna 

(Illinoian?) age in the central 

ments underlie terraced and channeled surfaces between major morainal belts on coastal low lands and 

in mountain valleys. The lacustrine sediments range in thickness 

from a few inches to at least 100 

feet. Many of the streams have 

built large deltas; other smaller 

streams have deposited sediments 

to form alluvial fans and alluvial 

fan deltas. Thick and extensive 

elevated tidal-flat and beach deposits occur in places along the 

coasts (pl. 1), particularly near 

l{enai and l{asilof. 

part of the zone (pl. 1). The moraines are mantled by a variable 

thickness of proglacial lake silt, 

sand, and gravel of Naptowne 

(classical Wisconsin) age. The 

proglacial lake deposits are thinner and coarser on the flanks of 

the moraine and become thicker 

and finer grained in the intermoraine areas of the lowland. Interbedded glacial, glaJciolacustrine, 

and glaciofluvial deposits, generally hundreds of feet thick, underlie the surface drift units and overlie bedrock of Tertiary age. 

The intensity of ground cracking and ground-water eruption 

varies within the zone. The areas 

of broken ground are separated by 

large areas in which surface cracks 

are inconspicuous or absent. No 

consistent relationship is apparent 

between ground cracking and 

either the local topography or the 

underlying stratigraphy. Within 

the zone the ground-cracked localities ooour (1) on terraced morainal slopes and crests underlain 

by thick sections of compact till 

1nantled by thin sand and gravel 

deposits, ( 2) on channeled plains 

bordering moraines and underlain 
F4 ALASKA EARTHQUAKE, MARCH 2 7, 1 9 6 4 

N 

Number of 

measurements 

2.-Azimuth-frequency diagram showing dominant trend of ground cracks in the Kenai Lowland resulting from the 1964 Alaska earthquake. Includes measurements of 139 cracks in the central part of 

the northeast-trending zone of ground breakage in the Kenai Lowland. 

by thick sections of predominantly 

fine- to medium-grained sand, (3) 

in intermoraine depressions underlain by sand and silt, and ( 4) 

on elevated tidal flats underlain by 

estuarine silt and sand. The cracks 

cut undeflected across small hills 

and depressions In morainal 

topography. 

The broken ground is characterized by a mosaic of ground cracks 

that trend in many directions. Locally the cracks show topographic 

control by slumping on slopes, but 

in many places no such control is 

evident. In all localities observed 

on the ground, the northeasttrending cracks were the most persistent and in many places could 

be traced diagonaily across slopes 

and ridges without apparent deflections in trend. Measurements 

of the most conspicuous crack directions in the southern half of 

the zone suggest preferred fracture trends of N. 50°-55° E. (parallel to the zone itself), N. 20°-

250 E., N. 0°-5° W., N. 10°-15° 

W., N. 30°-35° W., N. 50°-55° W., 

and N. 75°-80° W. (fig. 2). Examples of broken ground patterns 

within the zone are shown in figures 3 and 4. In forested areas, 

cracking of the ground split numerous trees (fig. 5). 

Most of the cracks within the 

zone ranged in width from knife 

edge to a foot (fig. 6). They were 

generally very sharp, vertical, and 

straight with abrupt angular 

changes in direction and sharp 

angular intersections with other 

cracks (fig. 7). Major cracks had 

many smaller branch cracks that 

intersected the main cracks at 

sharp acute angles or sometimes at 

right angles. In places, major 

cracks abruptly changed direction 

at crack intersections. Vertical and 

horizontal displacements occurred 

along some cracks; most were less 

than a foot but a few were as much 

as 2 feet (fig. 7). Most displacements appeared to be primarily the 

result of adjustments in the surficial materials by slumping and 

differential compaction, or of removal of underlying materials by 

ground-water eruption. 

F e a t u r e s associated with 

ground-water eruptions were common throughout the zone. These 

features included ridges and 

mounds of sand alined along 

cracks (fig. 8) ; sand sheets as 

much as 2 feet thick, locally covering acres of ground associated 

with the cracks (fig. 9) ; vents from 

which erupted sand either spread 

in all directions or was extruded 

primarily in one direction-and 

made a sand apron extending from 

the vent; collapse pits, as much as 

30 feet in diameter; and fissures as 

much as 20 feet wide and 25 feet 

or more deep (figs. 9, 10), resulting from the removal of material 

by copious outpouring of ground 

water. In a few places great outpourings of sand were followed by 

small extrusions of watery silt 

which formed low ( 2 to 3 inches 

high) silt ridges and mounds and 

irregular microrelief features on 

the surface of the sand (figs. 11, 

12). These silt extrusions must 

have occurred in the very last 

stages of the ground-water eruptions and after the main shaking 
60°35'55" 

GROUND BRE'AKAGE., COOK IN1IJET AREA, ALASKA 

'\ 

' I 

I ''{ 

I 'l( 

~-- I ' 

I I ' 

150"52'40" 

I 

I 

I 

APPROXIMATE SCALE 

I 

I 

I 

I 

I 

I 

I 

0 100 200 FEET 

EXPLANATION 

D 

Terraced and channeled sand plain 

Muskeg 

Ground-water eruptive 

~ 

~ 

deposits of sand and silt with 

pebbles of clastic coal and lignite 

Trends of main ground crack sets 

'"'"'"'"''""'''""" 

Margin of well-drained ground 

Craterlet which erupted ground water and sand 

8 

Letter indicates location of photograph 

3.-Ground cracks (loc. 1, pl. 1), Kenai Lowland. 

F5 
F6 ALASKA EARTHQUAKE, MARCH 27, 1964 

I 

I 

y 

/I 

(I 

\I 

I 

150°49'20" 

EXPLANATION 

D 

Forested, terraced, and channeled moraines underlain by variable thickness of stratified silt, sand, 

and gravel over till 

~ -

-

Muskeg underlain by 6-20 feet of peat and organic 

silt 

Ground-water eruptive deposits of sand and silt with 

pebbles of clastic coal and lignite 

D 

u 

Fault 

U, upthrown side; D, downthrown side 

0 50 100 FEET 

I I I I 

Open ground cracks 1-16 inches wide, 2-6 feet deep; 

locally displacements of 1-16 inches form graben 

(G) and horsts (H) 

-----=-----

Thin ground cracks cutting forest turf and peat 

deposits 

Pressure ridges of forested turf and peat formed by 

landsliding 

Collapse pits and fissures associated with erupted 

sand deposits 

Open ground cracks 

~ 

with 

~ 

associated eruption of sand 

and ground water 

---250'---

Topographic contour 

B 

Letter indicates location of photograph 

4.-Ground cracks (loc. 2, pl. 1), Kenai Lowland. 
GROUND BRE1

AKAGE, COOK J:NIDET AREA, AL~SKA 

5.-Tree split by ground cracking (loc. 2, pl. 1), Kenai Lowland. The grow1d crack which trends into the 

split in the tree (loc. A, fig. 4) cuts ·across the top of a small knoll in moraine. 

F7 
F8 ALASKA EARTHQUAKE, MARCH 27, 1964 

G.- 1'ypical large ground crack ( loc. 1, pl. 1), Kenai Lowland. Crack was 4 inches 

to 1¥2 feet wide; it cut a sand plain. Sand was not extruded along this crack 

(loc. A, fig. 3). 
GROUND BREAKAGE., COOK INLIET ARE'A, ALASXA F9 

8.-Sand ridges deposited along a 

ground crack (loc. 2. pl. 1) by eruption 

of ground water during the earthquake. 

A sand ridge on the right side of the 

picture intersects the main ridge at 

nearly right angles. Person has right 

leg in deep crack (loc. C, fig. 4). 

7.-Vertical displacement (loc. 2, pl. 1). 

A scarp more than 200 feet long and 2 

to 3 feet high wa'S produced in a thick 

section of frozen peat and organic silt 

(loc. B, fig. 4). Crack at the base of the 

scarp was 6 inches to 1 foot wide. Another crack intersects scarp at right 

angles; this displacement probably resulted from differential compaction and 

downslope extension of silty deposits in 

a muskeg bordering a small lake. 
9.- Large fissure at locality 2 (pl. 1). 

This fissure was 25 or moro feet deep 

and as wide as 20 feet in places. A 

thickness of 2 or more feet of sand 

which was extruded from the fissure 

can be seen around the tree. Photograph was taken at locality D (fig. 4). 

10.- Large ground crack with vertical 

displacement (loc. 2, pl. 1). Thick deposits of sand border the left side of 

the crack. Photograph was taken near 

E (fig. 4). 
26~-870 0-67--3 

GROUND BREAKAGE, COOK INil.IEri' AREA, ALASKA Fll 

H.-Microrelief features formed in extruded silt (loc. 2, pl. 1) . Area pictured 

is about 48 inches wide) 3-inch-long 

jackknife is slightly above center of 

picture). The delicate silt mounds and 

ridges were formed in the last stages 

of ground-water eruption on the surface of previous sand extrusions. 

12.-Small vent which extruded watery 

silt (loc. 2, pl. 1). Jackknife is 3 inches 

long. Near locality D (fig. 4), watery 

silt from small vents such as this was 

extruded in the last stJages of eruption 

and spread out over the top of previously erupted sand. 
F12 ALASKA EARTHQUAKE, MARCH 2 7, 1964 

had ceased, otherwise the small 

delicate microrelief features would 

not have been so well preserved. 

Although the greatest outpourings 

of sand were in relatively flat areas 

or depressions, some sand was extruded from cracks extending up 

the sides of small morainal hills. 

The deposits laid down by 

ground-water eruption within the 

zone are predominantly fine- to 

medium-grained sand. In most localities the sand contains scattered 

pebbles and cobbles of detrital coal 

and lignite as much as 6 inches 

long (fig. 13). The largest amounts 

of sand and much of the coal were 

commonly concentrated at the intersection of two or more major 

cracks or at the intersection of a 

wide and a narrow one. Many, if 

not all, of the coal fragments carried to the surface during the 

earthquate by ground water could 

have been deriwed from near-surface deposits that contain detrital 

coal originally derived from underlying Tertiary coal beds. However, derivation of some of the coal 

from the Tertiary coal beds at 

depths of several hundred feet, 

though unlikely, is not excluded 

as a possibility by present evidence. 

The quantity of sand deposited 

locally indicates copious groundwater discharge during the earthquake and suggests the tapping of 

large reservoirs. Sand and silt deposited on tree branches indicate 

that water was ejected out of some 

cracks to a height of at least 20 

feet. Ground-water supplies in the 

general area of the central part of 

the zone are obtained from gravel 

aquifers under hydrostatic head. 

The aquifers are 100 to 200 feet 

below the surface and beneath the 

surface till units. It is probable 

that ground cracking penetrated 

through the surface till units at 

many places and tapped these deep 

ground-water reservoirs. 

In several, but not all, places 

where the northeast-trending zone 

crossed roads, cracks were found. 

The zone crossed the paved Sterling Highway east of Soldatna, 

and several cracks in the pavement 

mere noted together with minor 

slumping in fill. Large cracks 

and large outpourings of sand 

occurred where the zone crossed 

the oil-well access road and several 

of the side roads connecting with 

it (pl. 1). 

Although this zone of ground 

breakage passed along the southern margin of the Swanson River 

oil field, no ground breakage was 

noted or reported from the field 

itself. Apparently the oil wells 

were not damaged or significantly 

disturbed by the earthquake. 

In the spring-fed Finger Lakes 

(about one-half mile southwest of 

loc. 2, pl. I), there was a gradual 

lowering of water during the summer following the earthquake, an 

occurrence which had not been observ.ed in previous summers. It was 

suggested that the lowering might 

be due to fissures in the lake bottoms or to a restriction of the flow 

of spring water as a result of the 

compaction of sediments (Alaska 

Dept. Fish and Game, 1965, p. 29). 

The lakes are in glacial moraine 

and the earthquake caused slumping on the sides of the moraines 

along the margins of the lakes. 

At several places within the 

zone, ancient collapse pits and 

linear troughs covered by mature 

forest vegetation record previous 

episodes of ground cracking and 

ground-water eruption. 

COASTS 

Much of the western coast of 

the Kenai Peninsula mas examined, and few changes attributable 

to the earthquake mere found. Although steep high bluffs of unconsolidated glacial deposits line 

much of the coast, there were no 

large landslides and very little 

slumping. 

At Kasilof, which is approximately in line with the northeasttrending zone of ground breakage 

previously described (p. P3), 

cracks as much as 1 foot wide were 

formed. The cracks were traceable 

for several hundred feet and cut 

sand dunes and beach deposits at 

the coast (fig. 14). Crack walls 

were generally sharp-in fact, exceptionally sharp for occurrence 

in loose sand. Some had small 

vertical displacements as much as 

10 inches high. They had the usual 

pattern of many branches and 

cracks intersecting from several 

directions. Collapse occurred along 

some cracks where large amounts 

of sand had been extruded (fig. 

15). Pressure ridges a few inches 

high and 2 to 3 inches across were 

noted in silt on tidal flats; some 

radiated from a central point in 

several directions for distances of 

25 feet or more. 

At Chickaloon Bay a complex 

network of cracks extended seaward from the shore and perpendicular to it onto the tidal flats. 

Major crack systems also paralleled the shore, but these were observed only from the air. Although 

the tidal flats at Kasilof and 

Chickaloon Bay were considerably 

fractured, other tidal flats in 

similar geologic and topographic 

situations had no ground breakage. 

For instance, no ground cracking 

was observed on the tidal flats at 

Kenai, Moose Point, Point Possession, Stariski, or in the Ninilchick area. 

On the mainland near Homer, 

ground fissures occurred in the 

bluff on which the U.S. Bureau of 

Land Management station is located. However, as elsewhere on 

the coast, ground breakage due to 

the earthquake was slight and less 

than might have been expected 

where steep slopes in materials 
GROUND BREAKAGE, COOK INLET AREA, ALASKA F13 

14.- Ground cracks at Kasilof in elevated beach deposits. Cracks were as 

much as 1 foot wide. Vertical displacement is evident along crack near man. 

Considerable clastic coal was brought 

up from beneath the surface and deposited with the sand. 

13.-Detrital coal extruded with sand 

(loc. 1, pl. 1). Copious amounts of sand 

were extruded from a fissure cutting a 

gravel road ( loc. B. fig. 3). Pieces of 

coal and lignite as long as 6 inches 

(some indicated by arrows) were extruded with the sand. 
F14 ALASKA EARTHQUAKE, MARCH 27, 1964 

15.-Collapse pits at Kasilof formed after eruptions of ground water and sand. 

Pit in foreground is about 3 feet in diameter. Erupted sand covers the ground. A 

large crack extends from the pits in the middle background. 

susceptible to sliding abound 

(Waller, 1966, p. D6-D7). Damage 

to Homer Spit, due largely to submarine sliding and flooding, has 

been described by Waller ( 1966). 

LARGE LAKES 

Tustumena Lake and Skilak 

Lake are the two largest lakes in 

the Kenai Low land (pl. 1). Tustumena Lake is 25 miles long and 3 

to 6 miles wide; Skilak Lake is 14 

miles long and has a ma.ximum 

width of about 4 miles. Both lakes 

occupy glacially scoured troughs 

that hwve been dammed by 

moraines. 

Ground cracking around these 

lakes was extensive in the large 

outJwash deltas at the heads of the 

lakes. Damage elsewhere along the 

shores of the lakes was minor, although the lakes are surrounded 

primarily by thick unconsolidated 

deposits of Quaternary sediments. 

The several small occurrences of 

ground cracking which were observed along Tustumena and 

Skilak Lakes were mostly in unstable slopes of alluvial fan deltas 

or at the tips of peninsulas or 

spits projecting into deep water. 

TUSTUMENA OUTWASH DELTA 

The outwash delta at the head 

of Tustumena Lake is 411z miles 

wide; it partly buries two groups 

of ice-rounded bedrock hills that 

divide the outwash plain into two 

branches with separate delta 

fronts (pl. 3). During the earthquake, both delta fronts failed by 

fracturing and slumping into the 

lake. 

Photographs obtained after the 

earthquake (fig. 16) indicate that 

a major zone of fissures oriented 

N. 5°-10° '\¥.formed subparallel to 

the southern delta front about half 

a mile from the lake shore. This 

break defined the inland margin of 

the pa·rt of the delta most disrupted by the earthquake. Much 

sand was extruded along this fracture zone and flowed out upon the 

snow-covered surface (fig. 16). 

The fracture pattern in the disrupted part of the delta consisted 

of two sets of diagonal fractures 

formed on northwest and northeast trends and a less well developed set formed about perpendicular to the main fissured 

zone. It is believed that this fracture pattern formed during the 

earthquake when the lakeward unconfined face of the delta extended 

forward and pulled away from the 

main mass of the delta. McCulloch 

has described and explained similar crack patterns in Rocky Creek 

and Lakeview deltas at Kenai 

Lake {1966, p. A35). 

The ground cracks in the outwash delta ranged in width from 

a fraction of an inch to 4 feet (fig. 

17). Most cracks showed no vertical displacement, but a few indicated subsidence of several inches 

to 11/z feet on the lake side. Little 

overall evidence of subsidence of 

the delta front was observed, and 

it is estimated to have been less 

than 10 feet. 

The southern edge of the outwash delta is bordered by a low 

forested terrace (pl. 3, fig. 16). 

Cracks 3 to 4 feet wide and 2 to 3 

feet deep spaced at intervals of 10 

to 50 feet cut through the forested 

area in a north-south direction 

along the lake edge. Many trees 

were split and offset along cracks, 

the offset indicating a right-lateral 

ground displacement of 1 to 3 feet. 

The walls of the deeper cracks exposed the following terrace stratigraphy from top to bottom :vegetation mat and organic silt about 

1 foot thick over stratified pebbleto-boulder gravel containing lenses 

and beds of sand and silt. 

Sand, silt, and some gravel were 

brought to the surface by forceful 

ejection of ground water from the 

cracks. The extruded material 

spread out to form large sand 

sheets covering a few acres. Elsewhere sand ridges were deposited 
GROUND BREIAKAGE, COOK IN[)ET AREA, ALA:S:KA 

16.-0utwash delta at head of Tustumena Lake a few days after the earthquake. View is south (pl. 3). The 

ground was snow covered, and water 

and sand erupted along major cracks 

(dark-gray areas) partly removing 

the ·Snow and covering the ground surface with sand. The cracked ice-covered 

lake surface is to the right. A major 

fissure system paralleling the delta front 

is seen to the left of center. Photograph 

by Avery Thayer, Fish and Wildlife 

Service, Kenai, Alaska. 

17.-Crack between delta front and 

bedrock at Tustumena Lake (loc. A. 

pl. 3) . A wedge of outwash deposits 

pulled away from the stable bedrock 

face during the earthquake S·haking. 

F15 
[%Old beach 

ALASKA EARTHQUAKE, MARCH 27, 1964 

cracks 

Lake level 

APPROXIMATE SCALE 

0 - 50 100 150 FEE1 

18.-Diagram showing type 

along the margins of the cracks. 

Locally, boulders as much as 8 

inches in long dimension were 

brought to the surface from the 

underlying gravel beds by the 

ejecting ground water. 

Such forceful ejection at this 

single locality may have been 

caused by conditions which differed slightly from those in the 

delta to the north. Water moving 

through the outwash terrace under 

higher hydrostatic head (probably 

because the surface gradient of the 

terrace is steeper than that of the 

bordering outwash) may have been 

confined between more firmly 

frozen sediment layers. The firmer 

freezing could obtain because of 

the thicker organic silt layer, continuous vegetation mat, and extensive forest cover. The difference in 

the pattern of cracking between 

the terrace and the outwash delta 

may reflect differences in the underlying bedrock topography. Because of the general configuration 

of this valley, the bedrock slope 

under the terrace may be northwestward and that under the outwash delta may be more to the 

west. Slippage of the lake front 

sediments over a northwest-sloping bedrock floor would explain 

the observed displacement. 

of ground dis~uption on the north shore of Tustumena Lake (loc. 3, pl. 1). 

The northern delta front was 

fractured in a pattern similar to 

that of the southern front, but less 

severely. The diagonal and perpendicular crack sets and the subparallel fissure zone separating the 

extended block from the inland 

part of the delta were present, but 

the patterns mere not as strongly 

developed as in the southern front. 

A considerable amount of sand was 

extruded along many of the fractures. The fracturing was apparently caused by lateral spreading 

of the deltaic sediments toward the 

lake as a result of the earthquake 

shaking. 

OTHER TUSTUMENA LAKE GROUND 

CRACKING 

Local slumping at the fronts of 

alluvial-fan deltas occurred at the 

mouths of Indian Creek, Moose 

Creek, and Bear Creek (pl. 1). 

Slumping took place largely by 

v e r t i c a 1 displacement along 

ground cracks parallel to the lake 

margin. At Windy Point a block 

of beach and terrace gravel 50 by 

100 feet slumped into the lake 

largely submerging spruce and 

birch trees 40 to 60 feet tall. Subparallel fractures 1 to 6 inches 

wide developed landward of the 

slump-block scarp. At the western 

end of Caribou Island the narrow 

tip of beach gravel cracked but did 

not slump. Ground cracking occurred over fairly large areas on 

shoreline terraces on opposite sides 

of the narrowest part of Tustumena Lake. 

Near Tanya Lake (loc. 3, pl. 

I), a northeast-trending set of 

ground cracks spaced 10 to 30 feet 

apart cut the beach deposits and a 

low forested gravel terrace. A 

graben 10 to 30 feet wide, about 

100 feet long, and downdropped 

4 to 6 feet formed and filled with 

water (fig. 18). Gravelly terrace 

deposits underlain by lake silt apparently broke into blocks along 

northeast fractures and slid lakeward upon a slightly inclined slip 

plane in the silt (fig. 18). The forward translation and slumping of 

the lakeward blocks permitted the 

interior block to drop down. This 

mechanism is similar to that described for some of the landslides 

in the Anchorage area (Hansen, 

1965). The submerged block with 

mature spruce trees indicated vertical slump of at least 20 feet at the 

shore. 

On the opposite shore of the lake 

(loc. 4, pl. I), a section of a low 

forested terrace 500 feet long and 

100 feet wide slumped toward the 
GBOUND BRE~~E., COOK LN(IIET AREA, ALASKA F17 

lake. The disrupted block is defined by an arcuate set of large 

fractures that intersect the lake 

margin at both ends; however, no 

displacement of bhe terrace is visible where the fractures meet the 

lake shore. Tilted trees occur on 

low ridges that appear to have 

formed by slight rotation along 

subordinate cracks in the block 

(fig. 19). Visible vertical displacements were slight, and modern 

beach deposits fronting the block 

were probably lowered only a few 

inohes relative to the unaffected 

beaches to the north and south of 

the slumped area. 

SKILAK LAKE 

The entire outwash plain between the front of Skilak Glacier 

and Skilak Lake was extensively 

fractured, and the delta front at 

the head of Skilak Lake slumped 

into the lake. The amount of 

slumping of bhe delta front below 

lake level is not known, but examination of aerial photographs and 

ground observations suggest that 

a segment of the delta front about 

half a mile wide may have subsided sufficiently to be partially 

submerged during the low mean 

lake-level phase. Aspen and brush 

10 to 20 feet high were standing in 

water 3 to 10 feet deep as muoh as 

1,000 feet offshore from the new 

shore line. However, the fact that 

no freshly ice-scoured trees or 

other evidence of major waterlevel changes were observed anywhere along the shores in the upper part of the lake suggests that 

the amount of material that 

slumped from the delta front at 

the time of the earthquake was not 

large enough to generate large 

waves. Fracturing of the outwash 

plain drained a beaver-dammed 

lake along the south side of the 

valley about 2 miles from the head 

of the Skilak Lake (Avery 

Thayer, written commun., 1964). 

The beach fronting the Pipe 

Creek alluvial-fan delta (Iw. 5, pl. 

1) ms cut by a system of intersecting fractures one-half inch to 

3 inches wide. The most conspicuous cracks trended north or 

nortrheast, that is, transverse to 

rather than parallel to the shore. 

At the lower campground (loc. 

6, pl. 1) near the outlet of Skilak 

Lake, ground cracks, mole tracks, 

and pressure ridges formed on a 

low forested terrace. The pressure 

ridges, 6 inches to 2 feet high, 

border the muskeg back of the 

campground and trend northwestward. The mole tracks developed 

by overthrusting (or underthrusting) of the forest litter layer; they 

are slightly offset along transecting cracks which trend northeast. 

This pattern suggests formation 

under compression, but the mechanism is not clear. In the absence of subsurface data, it cannot be determined whether the 

surface deformation resulted from 

stresses set up by slumping confined to the upper layers of the 

unconsolidated deposits or whether 

the deformation resulted from accommodation of the unconsolidated section to displacements at 

depth. The possibility of formation by movement of the lake ice 

during the earthquake must also 

be considered. 

The north- to northeast-trending 

beaches at the lower end of the lake 

were fractured in two places. At 

locality 7 (pl. 1) the cracks are 3 

inches to 1 foot wide and are confined to the modern beach gravel 

deposits. The largest crack was at 

the base of the scarp defining the 

inner edge of the beach. It was 

intersected by a few transverse 

cracks that extended diagonally 

across the beach toward the lake. 

At locality 8 (pl. 1) a north- to 

northeast-trending crack 5 to 15 

inches wide cut diagonally across 

the beach and was traceable into 

higher ground a few hundred feet 

from the lake before being lost in 

dense forest. 

SOUTHERN INTERIOR 

Ground breakage in the interior 

of the Kenai Lowland outside of 

the northeast zone was limited to 

a few scattered localities (pl. 1) 

where the following types of disruption mere observed : 

1. Landslides in unconsolidated 

deposits on moderate to steep 

slopes. Northeast of Homer. 

2. Large - avalanches. Anchor 

River. 

3. Slumps in unconsolidated deLake level posits on or toward unconfined faces such as river 

banks, lake shores, and delta 

fronts. Chakok River, Box 

River, Tustwnena Lake, Ski- APPROXIMATE SCALE 

0 25 50 75 FEET lak Lake, and Stariski Creek. 

IIIIII I I 4. Ground cracks in lowlands cov19.-Diagram showing a type of slumping on the south shore of Tustumena Lake ered by silty lake deposits, 

(lot. 4, pl. 1). alluvium, or fluvioglacial de- 
F18 ALASKA EARTHQUAKE, MARCH 2 7, 1 9 6 4 

APPROXIM ATE SCALE 

1 M ILE 

L_L_~~~--~ 

N 

EXPLANATION 

Valley train 

Alluvial terrace and 

glacial moraine. Dark 

lobes are Recent moraines 

Rock glacier or moraine 

Area of slope deposits 

Ground cracks produced 

by earthquake; associated locally with 

ground-water eruptive 

deposits 

® 

Collapse pit produced by 

the earthquake 

••• 

Sites of unusually persistent avalanching 

20.-Sketch map of IDklutna valley showing sites of perSii.stent avalanching and location of ground breakage. 

posits. Upland in headwaters 

of Bear Creek. 

5. Ground ·cracks and pressure 

ridges in muskeg areas. Half 

a mile south of Clam Creek, 

Slikok Creek. 

6. Cracks in flood plains and valley trains underlain by sand 

and gravel. Skilak River, Fox 

River. 

The cracking in the Fox River 

flood plain was particularly spectacular on the alluvial fan formed 

'at the confluence between Sheep 

Creek and the Fox River. Copious 

amounts of sand erupted along an 

extensive mosaic of cracks. Along 

the channels of the Fox River, 

numerous alluvial deposits on 

slip-off slopes were broken along 

longitudinal and t r an s v e r s e 

cracks. The alluvial flats on the inside of meanders were cracked nnd 

channel banks sl urn ped at n umerous places. The cracking appeared to be concentrated along 

the axis of the Fox River valley. 

No flood-plain failures were apparent in tributaries heading m 

the Kenai MountJains. 
GROUND BRE1AKAGE, COOK INIJEfi AREA, ALA:SKA Fl9 

NORTHERN COOK INLET 

AREA 

The major ground breakage in 

the northern Cook Inlet ,area was 

in and around Anchorage and 

Portage. Ground cracks and landslides were abundant and destructive and have been described in 

de1Jail by Hansen ( 1965), McCulloch ( 1966) , Kachadoorian 

(1965) and others. Ground breakage in this area also occurred in 

the Eklutna valley, around Lake 

George, in valleys in the western 

Chugach Mountains, and west of 

Anchorage including the delta of 

the Susitna River. 

At the head of Eklutna valley, 

unusual avalan0he activity followed the earthquake. It began 

after the earthquake and continued throughout the summer of 

1964. Periodic observations made 

in the valley by U.S. Geological 

Survey personnel stationed in 

Anchorage indicate that it commenced again after the spring 

thaw in 1965 and continued 

throughout that summer. As late 

as August 2,1966, minor avalanche 

activity was reported (Ruth 

Schmidt, written commun., 1966). 

However, the total activity in tJhe 

summer of 1966 was apparently 

considerably less than that in 

1964, hut more than before the 

earthquake. 

In the early part of the summer 

of 1964, rock debris ca.scaded 

nearly continually from three 

principal places on the steep high 

cliffs above Eklutna valley (fig. 

20). Talus cones at the base of the 

cliffs were much enlarged (fig. 

21). Dense dust clouds emanated 

from the avalanches and resulted 

in erroneous reports of volcanic 

eruptions when spotted by airplane pilots (figs. 21, 22). Later in 

the summer, several of the avalanches became inactive, and by 

August 1965 activity was largely 

21.-Sites of avalanche activity in Eklutna valley. These talus cones were present 

before the earthquake but have been enlarged by avalanche activity since the 

earthquake. The dust clouds are created by the aV'alanching. 

22.- Dust cloud in Eklutna valley caused by avalanche activity. The avalanching 

has been persistent during the summers since the earthquake. 
23.-Cr<ack in gravel outwash iru Eklutna valley. Orack was about 10 inches wide 

and split a tree stump. The two halves of the stump were offset about 14 inches. 

restricted to one avalanche chute 

at the head of the Vlalley. Karl 

Gladys (oral commun., 1964) estimated that the normal avalanche 

activity, which usually lasts 2 to 

3 weeks after spring thaw, constituted less than 2 percent of the 

avalanche activity during the summer of 1964. The remainder is attributed to disruption caused by 

the earthquake along shear zones. 

Ground breakage was noted on the 

high terraces in the valley bottom 

below the northernmost avalanche 

source. One conspicuous set of 

cracks had a southeastward trend 

and crossed moraines, outwash, 

and colluvial deposits. An intersecting set trends northeast. 

Ground breakage was also present on the floor of the valley at 

the head of Eldutna Lake. An extensive mosaic of cracks was 

present in the gravel outwash, and 

much sand and gravel erupted with 

the ground water during the earthquake. Fissures were as wide as 

1% feet. Horizontal offsets as 

much as 2 feet and vertical offsets 

of 1 foot were observed. Trees were 

split and offset aJong some cracks 

(fig. 23). Circular pits 41;2 feet in 

diameter and as much as 12 feet 

deep squirted sand and water 

(Karl Gladys, written commun., 

1964). The main zone of cracking 

at the head of the lake covered an 

area of about 1 square mile. Additional damage in the Eklutna area, 

particularly to the power-plant installa.tions at the lower end of 

Eklutna Lake, is described by 

Logan (1967). 

Within the Lake George basin 

of the Chugach Mountains 28 

miles southeast of Palmer, damage 

resulting from the earthquake included failure along the fronts of 

deltas built at the mouths of two 

tributary valleys, and extensi'v.e 

cracking associated with eruptive 

deposits of emerged bottom sediments at the head of the lake. 

The most extensive disruption occurred along the front of the Troublesome Creek delta where slumping caused lakeward rotational 

displacements of frozen gravel 

blocks as much as 20 feet wide and 

100 feet long. Chaotic topography 

resulted (figs. 24, 25). The delta 

at the mouth of a creek entering 

the south end of upper Lake 

George failed by cracking along 

the margin of the delta front. 

Lateral extension, however, was 

slight, minor vertical or lateral 

displacements being evident along 

the cracks. 

A mosaic pattern of cracks developed in the exposed lake-bottom 

sediments near the head of the lake 

(lake-bottom sediments were exposed at the time of the observations because lake levels were low). 
24.-Failure of the delta front at Troublesome Creek, Lake George (loc. C, fig. 25). Man is standing on a large slumped and 

rotated block that is bounded front and back by large fissures. 

61° 15' 

EXPLANATION 

Outwash 

Moraine of Recent age 

Emerged lake bottom sediments; line pattern 

indicates areas of severely cracked sediments and eruptions of silt, sand, and water 

from cracks 

• 

Front of delta that failed during earthquake 

Earthquake cracks paralleling front of moraine 

l!!llllllll!!ll!!l!!l ! ! 

Margin of bedrock areas 

A 

Letter indicates location of photograph 

25.- Lake George area showing location of ground breakage. 
ALASKA EARTHQUAKE, MARCH 27, 1964 

26.-Wall of silt punched up on the emerged bottom of Lake George. The wall was 8 to 24 inches high, 30 

feet long, and 6 inches wide (loc. B, fig. 25). 

27.-Ridges of silt squeezed up along mclrs in the emerged bottom sediments of Lake George (lw. A. fig. 25). 
GROUND BREAKAGE:, COOK INILIET ARE'A, AL.AISKA F23 

Lake silt was squeezed out of the 

underlying water-saturated sediments and erupted through cracks 

in the seasonally frozen surface 

layer. At one locality a wall of 

frozen silt, 6 inches wide and about 

30 feet long, was punched up 8 to 

24 inches by pressures in the underlying unfrozen 1naterials during the earthquake (fig. 26). The 

undisturbed structure of the fine 

laminated silts exposed in the wall 

indicated that the silt must have 

been rigid and frozen at the time 

of displacement. Disruption and 

minor dislocation of the wall along 

northeast-trending cracks indicate 

subsequent development of and 

minor displacements along cracks 

that cut transversely the northwest 

set of parallel fractures that defined the wall structure itself. At 

several locations, mounds of silt 

1 to 2 feet high and 2 to 3 feet in 

diameter and showing internal 

flow structure formed at the intersection of the cracks. Unfrozen silt 

was squeezed up as ridges along 

some of the cracks (fig. 27). On 

the north side of the moraine along 

the south side of lower Lake 

George, some sand eruption occurred at the contact of the moraine with the lake sediments 

through cracks transecting the 

moraine. 

Reconnaissance observations 

within the Chugach Mountains between Knik Valley and Turnagain 

Arm revealed only two other localities of ground breakage: cracks 

cutting forest turf on thin alluvium over bedrock near the mouth 

of south fork valley of Campbell 

Creek and cracks in thick muskeg 

and alluvial deposits in the middle 

part of Eagle River valley (pl. 2). 

The major crack set in Eagle River 

valley was roughly parallel to the 

axis of the valley, and the most 

conspicuous transverse set of 

cracks trended at right angles to 

the valley axis. No ground damage 

was observed upvalley or downvalley from these cracked zones. 

Ground observations were not 

made in the other valleys of the 

mountain range. 

West of Anchorage, tidal flats 

were cracked and slumping occurred at the mouth of Knik Arm 

on the west side. The delta of the 

Susitna R i v e r was severely 

cracked; parts of its front subsided into Cook Inlet. In some small 

lakes in the Susitna River lowland, the sediments in the bottoms 

of the lakes were cracked. At the 

base of Mount Susitna along the 

projected trace of the Lake ClarkCastle Mountain fault, sand eruptions occurred along the margins 

of lake terraces cut in till. To the 

northeast about 18 miles, also 

along the trace of the Lake ClarkCastle Mountain fault, there was 

disruption and slumping along a 

bluff face. 

NORTHWEST SIDE OF 

COOK INLET 

Limited observations on the 

northwest side of Cook Inlet indicate that ground breakage was 

relatively minor and confined 

mostly to deltas, tidal flats, and 

alluvial flats, and occurred in 

widely scattered localities. Ground 

breakage was noted in the following places (pl. 2) : 

1. Beluga Lake. Beluga Lake is 

divided into upper and lower 

parts by deltaic outwash 

sediments d ep o sited by 

drainage f~om Capps Glacier. This outwash delta was 

considerably fractured. At 

the head of upper Beluga 

Lake, terraces along outwash 

channels cut below the main 

surface level of the large 

outwash delta were locally 

fractured. At the head of 

lower Beluga Lake a large 

block slumped into the lake 

submerging trees. M i n o r 

fracturing occurred at the 

outlet of lower Beluga Lake. 

2. Inland from Trading Bay, 15 

miles to the northeast. Extensive fracturing occurred 

in a zone extending northeast more or less parallel to 

the shore of Trading Bay 

and along the approximate 

postulated trace of the Lake 

Clark-Castle Mountain 

fault. The zone is about 12 

miles long. The dominant 

trend of the fractures is also 

northeast. Much sand was 

extruded along many of the 

fractures. 

3. Northeast shore of Chakatchama Lake. Cracks occurred in beach deposits 

along the shore of the lake 

(Gordon Giles, written commun., 1964). 

4. Tyonek. Lake ice and muskeg 

were cracked. About 5 miles 

north of Tyonek, old slumps 

along the coast were reactivated, but displacement was 

less than 1 foot. 

5. Trading Bay. On the coast Ph 

miles east of Kustatan, small 

slumps occurred in bluffs of 

glacial till (George Plafker, 

oral commun., 1966). 

6. Redoubt Bay. Cracks were 

common along the Drift 

River from the mouth inland 2 miles or more. All 

breakage was in alluvium. 

North from the mouth of 

Drift River, cracks associated with extruded sand occurred along the coast for a 

distance of about 2 miles 

(George Plafker, oral commun., 1966). 

7. Near the mouth of Tuxedni 

Channel. On the south side, 

cracks formed on steep 

slopes. Two months later, 

following spring thaw, landslides occurred in the cracked 

terrain (George Plafker, 

oral commun., 1966) . 

8. North shore of Tuxedni Bay. 

Along the east side of 
F24 

Squarehead Cove, the bluff 

:face sloughed off along the 

shore :for about 1 mile 

(George Pla:fker, oral commun., 1966). 

9. l{algin Island. Slumps developed in unconsolidated deposits on the south end. 

10. Augustine Island. Cracks more 

or less parallel to the coast 

were noted :from the air on 

the north end and on the 

northeast side. All appeared 

to be in recent unconsolidated deposits o:f volcanic 

sand, gravel, and bouldery 

gravel. Some o:f the cracks 

ALASKA EARTHQUAKE, MARCH 27, 1964 

were close to the shore, 

others were higher on the 

slope and subparallel to it. 

Slumps and small slides occurred in places along the 

cracks, and the surface was 

"stepped" downward toward 

the coast along some cracks 

(Bruce Reed and George 

Pla:fker, oral commun., 

1966). 

SOUTHEAST SIDE OF 

KACHEMAK BAY 

Ground breakage at two places 

along the southeast side o:f Kachemak Bay was noted by Pla.:fker in 

a reconnaissance flight in 1964 

(George Plafker, oral commun., 

1966; pl. 2). Extensive :fracturing 

resembling that o:f Skilak Lake 

occurred in the outwash delta at 

the head o:f Bradley Lake. Fine 

closely spaced cracks were noted 

in the tidal flats along the south 

shore o:f China Poot Bay. A rockfall took place on a steep cliff 

nearby. The outwash flats along 

the glacial drainage which enters 

China Poot Bay from the south 

were considerably fissured. Ground 

breakage extended :from the bay 

margin inland along the drain-

~age :for about 2 miles. 

CAUSES OF GROUND BREAKAGE 

The northeast-trending zone o:f 

ground breakage in the Kenai 

Lowland may not be caused entirely by simple lateral movements 

or compaction in unconsolidated 

sediments. Several :features indicate that additional :factors were 

involved. For example, in many 

places there is no consistent relationship between the cracks and 

either the local topography or 

stratigraphy; the cracks are unusually deep and are very persistent and have a marked linear 

trend. 

The :following explanations :for 

these :features are suggested : ( 1) 

The disrupted zone may have resulted :from movement triggered 

by the earthquake along a buried 

:fault. (2) There may have been 

differential compaction o:f Quaternary sediments along a buried 

ridge o:f Tertiary rock. (3) Gravity sliding may have taken place 

along the interface between the 

unconsolidated Quaternary deposits and the Tertiary bedrock. 

( 4) A combination o:f these processes could have been involved. 

The subsur£ace data available 

to the authors are insufficient to 

define clearly the bedrock structures beneath the Kenai Low land, 

but some o:f the data suggest a 

buried :fault; none preclude the 

possibility o:f such a :fault. Field 

mapping in the l{enai Lowlands 

(I{arlstrom, 1964) shows that the 

top o:f the Tertiary bedrock along 

the coast generally is above sea 

level south of, and below sea level 

north of, Kasilof. Thus there could 

be either an erosional break or a 

structural dislocation o:f the bedrock floor where the inferred :fault 

zone crosses the coast. 

In the Swanson River oil field, 

oil and gas have been produced 

:frmn the Tertiary sedimentary 

rocks northwest of the zone of disrupted ground. To date, all wells 

drilled south o:f the zone have been 

dry. This change in subsurface 

conditions may be due to a :fault, 

or it may indicate a :facies change. 

By report, seismic profiles obtained :from the northern part o:f 

the l{enai Lowland are difficult to 

interpret because o:f poor signal 

returns. They do suggest, however, 

an important subsurface discontinuity, either lithologic or structural, that approximately coincides in position with the zone of 

broken ground developed during 

the 1964 earthquake. At one place 

along the trace o:f this discontinuity the seismic data can be interpreted as recording a basement 

:fault o:f northeast strike, a steep 

southeast dip, and a downdropped 

south block (C. E. Kirschner, oral 

commun., 1964). 

The unusual avalanche activity 

at the head o:f Eklutna valley :following the earthquake and continuing into the summer o:f 1966 

might also be related to movement along faults. The rocks in 

this area are highly sheared and 

crushed. I:f these rocks were made 

unstable by small movements 

along :faults, the avalanche activity could have been set in motion. Furthermore, the continued 

avalanche activity might be due to 

minor readjustments in the disturbed blocks :following the main 

displacement. Although the bedrock o:f this looality has not been 

mapped in detail, the :fractured 

rock suggests that :faults are present. I:f simple displacement o:f 

sheared blocks took place as a result o:f the shaking o:f the earthquake without :faulting, it seems 
GROUND BRE'AKAGE, COOK SNILIE,T AREA, ALASKA F25 

unlikely that the avalanching 

would have continued so long. The 

disruption in the vialley floor at 

the head of Eklutna Lake and the 

damage to the powerplant facilities (Logan, 1967) also suggest 

that more than just the usual seismic effects from a distant earthquake were in operation here. 

On the northwest side of Cook 

Inlet northwest of Trading Bay, 

a concentration of cracks and sand 

extrusions in flood-plain deposits 

was noted near the projected trace 

of the Lake Clark-Castle Mountain fault. To the northeast of this 

locality along the trend of the 

fault, two other localities of disruption were noted within the 

Cook Inlet area. This ground 

breakage may be indicative of 

movement, along the Lake ClarkCastle Mountain fault, but other 

evidence of fault movement, particnlarly in bedrock, has not been 

detected. 

The remainder of the ground 

breakage in the Cook Inlet area 

can be explained by the presence 

of thick sections of silt and waterlogged sediments which are particularly susceptible to disruption 

by seismic activity when in topographically unfavorable situations. Despite many such unfavorable situations in the Kenai LOWland and the mountains bordering 

it, the overall ground breakage in 

this area was relatively minor. 

This stability may be explained, at 

least in part, by the fact that the 

ground was still firmly frozen at 

the time of the earthquake. 

CRUSTAL CHANGES IN THE COOK INLET AREA 

I 

I Crustal deformation that accompanied the 1964 earthquake affected an area of 65,600 to 77,200 1 square iniles in south-central 

Alaska. The deformation consisted 

I of two major northeast-trending 

I zones of uplift and subsidence bctween the Aleutian Trench and the 

i 

I Aleutian volcanic arc (Plafker, 

I 1965, p. 1686). Most of the Cook 

Inlet area is in the depressed area, I but the region also includes areas 

ranging from those with no detect- I able change to some on the northwest side of Cook Inlet that 

are slightly uplvarped. However, I maximum change in the Cook InI let area was small, probably not 

i more than 6 feet, as compared with 

50 feet to the southeast. 

OBSERVED COASTAL 

CHANGES 

I Coastal observations in the Cook 

I Inlet area indicate the following 

approximate changes in land-sea I 

levels : 

I 1. Along the south shore of Turnagain Arm near Hope, there 

was 4 to 6 feet of subsidence. 

Vegetated areas previously 

above storm beach levels were 

inundated during high tides 

following the earthquake. 

Houses in the low-lying parts 

of Hope were flooded. Inundation during high spring 

ticies extended to just be lo^^ 

the entrance of the General 

Store. High-water marks on 

forested slopes of a thick section of coarse alluvial fan east 

of Hope indicate inundations 

approximately 5 feet above 

the preearthquake high-tide 

mark (fig. 28). The coarse 

gravel substratum in the area 

and the absence of cracking 

or slumping along the coast 

suggest that most, if not all, 

of the recorclecl subsidence resulted from crustal subsidence and not from compaction or sl~lmping of the surficial deposits. 

2. Along the south shore of Turnagain Arm in Chickaloon 

Bay, there was 3 to 4 feet of 

subsidence. Vegetated elevated tidal flats previously 

above the reach of high tide 

were inundated following the 

earthquake. The estimate of 

3 to 4 feet of subsidence is 

based on observed changes in 

tidal levels in relation to the 

floor of a hunter's cabin in 

28.-Postearthquake high-tide rnnrlc along Turnagain Arm sea bluffs near Hope. 

Arrows indicate the pre- and postearthquake high-tide positions. The vertical distance of about 8 feet between these two pasiitions approximates the amount of 

crustal subsidence that accompanied the 1% earthquake. 
Fa6 ALASKA EARTHQUAKE, MARCH 2 7, 19 64 

the area that was for the first 

time partly inundated during 

the high tides (Avery Thayer, 

oral commun., 1965). However, a thick section of finegrained deposits underlies the 

tidal flats, so there is a possibility that part of the observed subsidence may have 

resulted from compaction. 

3. Along the east coast of Cook 

Inlet from Point Possession 

to Anchor Point, observed 

subsidence ranged from a little less than a foot to none 

it all. Undercutting of the 

stabilized and vegetated colluvial slopes along the sea 

bluffs was approximately the 

same as had been observed by 

Karlstrom during s p r i n g 

traverses in previous years. 

Vertical rellations between 

storm beaches, elevated tidalflat surfaces, and postearthquake high-tide levels appeared comparable to those 

observed in previous years 

near Point Possession, Moose 

Point, Kenai, Kasilof, Ninilchik, and Anchor Point. Local fishermen estimated a subsidence of about half a foot 

near Ninilchik on the basis of 

apparent changes in low tides. 

Careful observations on a pier 

gage at the cannery on the 

south side of the mouth of the 

Kenai River indicated that 

water levels during the spring 

high tides *following the 

earthquake did not quite 'attain the levels reached during 

the high tides of the preceding fall (Clarence Platt, oral 

comrnun., 1964). B 0 c a u s e 

high tides in this area are 

normally higher in fall than 

in spring, this observation is 

consistent with the geologic 

evidence of very little or no 

change in datum along the 

coast. A postearthquake resurvey of the highway from 

Kenai southwest to Ninilchik 

indicated no measurable 

change that could be attributed to regional warping during the earthquake (Alaska 

Highway Dept. personnel, 

oral commun., 1964). Shortterm postearthquake tidalgage records s u g g e s t a 

subsidence of 0.9 foot near 

Nikishka (Small, 1966, p. 20). 

4. Along the south coast of the 

Kenai Lowland between Anchor Point and Homer Spit, 

regional tilting ranged from 

none to less than 1 foot of 

subsidence at Anchor Point, 

2 feet at Homer, and 4 to 6 

feet at the tip of Homer Spit. 

These figures are based on a 

rapid resurvey of the highway after the earthquake by 

the Alaska Highway Department. Of the 4 to 6 feet of 

subsidence at the end of 

Homer Spit-a low sand and 

gravel bar that extends 5 

miles southeastward into Kachemak Bay from Homer-a 

minimum of 2 feet has been 

attributed to crustal subsidence and the remainder to 

differential compaction of 

the underlying unconsolid at e d materials (Grantz, 

Plafker, and Kachadoorian, 

1964, p. 9,24). 

5. Along the west shore of Cook 

Inlet from Point McKenzie 

to Kamishak Bay, there was 

1 to 2 feet of subsidence along 

the slumped front of the 

Susitna Delta area ; no change 

to slightly down near Tyonek; 1 to 2 feet of uplift 

along the coast of Kamishak 

Bay. The estimate of subsidence in the Susitna Delta area 

is based on observations of 

postearthquake tidal changes 

at a hunter's cabin by personnel of the Fish and Wildlife 

Service (Theron Smith, oral 

commnn., 1964). Probably 

most of this subsidence can 

be attributed to slumping and 

compaction of the delta front 

and adjoining elevated tidal 

flats between the Susitna 

River and McKenzie Point. 

This conclusion seems reasonable because (1) the coastal 

m a r g i n was extensively 

cracked during the earthquake and (2) changes in 

bathymetry of the bordering 

seaway (determined by U.S. 

Coast and Geodetic Surveys 

in the summers of 1963 and 

1964) record a major slump 

of material along the coast, 

presumably resulting from 

the earthquake. No changes 

were observed along the coast 

near Tyonek except in one 

area where subsidence of 

storm beaches suggested a 

downdrop of about 1 foot. 

This area of obvious subsidence occurs at the foot of a 

section of coastal bluff where 

large preearthquake slump 

blocks moved locally during 

the quake. The anomalously 

low tide levels following the 

earthquake that were reported by residents Iliamna 

and Tuxedni Bays suggest an 

uplift along the Kamishak 

Bay coast of 1 to 2 feet. 

The estimates of land-sea 

changes along the south shore of 

Turnagain Arm are of the same 

order of magnitude as the changes 

determined by releveling bench 

marks in bedrock along the north 

shore of the arm. This agreement 

suggests that the estimates elsewhere in the area based on shoreline relations may also be approximately correct. 

TILTING OF LAKE BASINS 

The large lake basins in the 

Cook Inlet area serve as natural 
GROUND HRE1

AKAGE:, COOK J.NlL/EiT ARE'A, ALASKA F27 

tiltometers because their long directions are n1ore or less parallel 

to the known direction of regional 

tilt. Regional tilting should be detectable in changes of water-plane 

levels. The positions of preearthquake water levels were checked in 

a few of the lake basins by referring to established bench marks. 

A preliminary resurvey of bench 

marks in relation to lake levels 

after the earthquake indicated 

southeastward tHting of Eklutna 

Lake; the head of the lake was possibly down 1 to 2 feet relative to 

its mouth (Russell Wayland, written commun., 1964). There was 

little or no tilting of Lake Chakatchama (Gordon Giles, written 

commun., 1964) ; and little or no 

tilting of Bradley Lake near 

Homer (Marvin Slaughter, written commun., 1964) . 

Air reconnaissance observations 

made of Tustumena Lake immediately after the earthquake suggested southeastward tilting of the 

I a k e basin. Outlet drainage 

through the Kasilof River was reported to have decreased to such 

an extent that the day following 

the earthquake a galosh-shod biologist was able to walk up its channel (Alaska Dept. Fish and Game, 

1965, p. 29). Forested areas at the 

lake head were reported to have 

been submerged. At the time of a 

2-day boat traverse around the 

margins of the lake in J nne 1964, 

lake level was below the normal 

seasonal level (Joe Magargl, oral 

commun., 1964). It was about 5 

feet below the average late autumn 

high -lake level, as marked by the 

inner edge of generally barren 

gravel beaches and by conspicuous 

high-water marks on rocky cliffs 

along the margin of the lake. SubInerged trees were found to be associated only with locally disturbed and slumped shoreline 

deposits; in no area could the submerged vegetation be related to 

regional tilting. Hand-leveling by 

Brunton compass at numerous localities about the margin of the 

lake revealed no systematic differences in the vertical interval between lake level and high-water 

beaches and watermarks. Thus, if 

the lake basin had been tilted, the 

amount of tilting was apparently 

less than the accuracy of measurement by Brunton compass, which 

is estimated to be + 1 foot. 

Observations made at the head 

of Tustumena Lake during the 

earthquake (Joe Secora, oral commun., 1964) indicate that the 

frozen surface of the lake cracked 

into a mosaic fracture pattern as 

the lake level rapidly rose and fell. 

Lake level receded about 2 feet 

and then rose ; sloshing of the lake 

waters continued for about 2 

hours. General lake level was 

judged to have been somewhat 

lower during the following day or 

two and then to have risen to about 

half a foot higher than the preearthquake level. Whether this 

rise resulted from belated tilting 

of the lake basin or from the normal inflow during increased 

spring thaw is not clear. Mr. 

Secora's account, however, is consistent with the later crude Ineasurements on shoreline features 

which suggest that tilting was 

probably less than 2 feet and conceivably less than 1 foot over a distance of 25 miles between the 

mouth and head of the lake. 

Similar geologic observations 

and Brunton compass measurements made in June 1964 along the 

margins of Skilak Lake suggest 

the same general amount of regional tilting during the earthquake as on Tustumena Lake. Extensive flooding of forests >around 

the margins of Skilak Lake was 

observed by local pilots in September 1964. A subsequent boat 

traverse around the lake margin 

by Avery Thayer (written commun., 1964) revealed unusually 

high lake levels hut no changes 

that could be attributed to differential tilting. However, Kenai 

Lake, about 25 miles east of Skilak 

Lake in the Kenai Mountains, was 

in a zone of greater deformation 

and showed about 3 feet of tilt 

(McCulloch, 1966, p. A29). 

PATTERN OF SUBSIDENCE 

The combined geologic observations and instrumental releveling 

data in the Cook Inlet area, together with data from adjoining 

areas, indicates differential subsidence, maximum crustal depression occurring along a linear zone 

between Portage and Aialik Bay 

or approximately coincident with 

the axis of the Kenai Mountains 

(Plafker, 1965). U.S. Coast and 

Gl~odetic Survey releveling indicah~s that maximum subsidence 

(nearly 6 feet) oocurred near 

Portage and that the amount of 

subsidence diminishes progressively to about 2 feet northwestward towards Anchorage (U.S. 

Coast and Geodetic Survey, 1966, 

p. 122) . These data indicate regional tilting to the southeast, approximately at right angles to the 

axis of the J{enai Mountains. The 

gradient of regional tilt is about 

0.1 foot per mile between Anchor 

Point and the Homer area, and increases to 0.2 foot per mile between 

Homer and Aialik Bay where the 

greatest subsidence ( 71h feet) 

measured in the region occurred 

(George Plafker, written commun., 19·66). The releveling and 

geologic data ~are insufficient to exclude the possibility of some local 

vertical fault displacements, but, 

in general, subsidence appears to 

have resulted largely from downwarping or folding of the crustal 

rocks. 

The line of zero change separ·at-
F28 

ing the depressed area of Cook Inlet from the more stable area to 

the north can be only approximately located by the available 

Ground breakage in the Cook 

Inlet area occurred largely in unconsolidated deposits. It consisted 

of slumps toward unconfined faces 

such as river banks, delta fronts, 

and lake shores; ground cracks in 

low land and valley bottom surfaces ; transverse and marginal 

cracks in modern and elevated 

tidal flats; and cracks in muskeg 

areas. Most of these breaks can be 

attributed to various processes and 

combinations of them such as differential com paction and downslope movements of underlying 

water-saturated fine-grained sediments. However, distribution of 

this type of damage was irregular, 

Alaska Department of Fish and Game, 

1965, Post-earthquake fisheries evaluation ; an interim report on the 

March 1964 earthquake effects on 

Alaska's fishing resources: Juneau, 

Alaska, 72 p. 

Dutro, J. T., Jr., and Payne, T. G., 1957, 

Geologic map of Alaska: U.S. Geol. 

Survey, scale 1 : 2,500,000. 

Grantz, Arthur, Plafker, George, and 

Kachadoorian, Reuben, 1964, Alaska's 

Good Friday earthquake, March 27, 

1964, a preliminary geologic evaluation: U.S. Geol. Survey Circ. 491, 35 p. 

Hansen, W. R., 1965, Effects of the 

earthquake of March 27, 1964, at 

Anchorage, Alaska: U.S. Geol. Survey Prof. Paper 542-A, p. A1-A68. 

Kachadoorian, Reuben, 1965, Effects of 

the earthquake of March 27, 1964, at 

'Vhittier, Alaska: U.S. Geol. Survey 

ALASKA EARTHQUAKE, MARCH 2 7, 1 9 6 4 

data. Apparently the line of zero 

change passes southwestward 

across the Susitna Lowlands, a 

few miles west of Tyonek 1and into 

CONCLUSIONS 

and localities with seemingly similar conditions were not necessarily 

similarly affected. Many areas, 

such as steep bluffs of unconsolidated materials along sea coast, 

were notable for their lack of visible earthquake effects. Regional 

structural elements may have had 

some control over the location and 

type of damage incurred in the 

Cook Inlet area, particularly in the 

northeast-trending zone of ground 

breakage in the Kenai Lowland. 

Here, disruption in a thick sequence of unconsolidated deposits 

may have been due to movement 

along a fault in the underlying 

Tertiary rocks. Faulting or adjustREFERENCES CITED 

Prof. Paper 542-B, p. B1-B21. 

Karlstrom, T. N. V., 1964, Quaternary 

geology of the Kenai Lowland and 

glacial history of the Cook Inlet region, Alaska: U.S. Geol. Survey Prof. 

Paper 443, 69 p. 

Logan, Malcolm, 1967, Effects of the 

March 27, 1964, Alaska earthquake 

on the Eklutna hydroelectric project, 

Anchorage, with a section .on Television examination of earthquake damage to underground communication 

and electrical systems in Anchorage, 

by Lynne R. Barton: U.S. Geol. Survey Prof. Paper 545-A, p. A1--A30. 

McCulloch, David S., 1966, Slide-induced waves, seiching and ground 

fracturing caused by the earthquake 

of March 27, 1964, at Kenai Lake, 

Alaska: U.S. Geol. Survey Prof. Paper 

543-A, p. A1-A41. 

Cook Inlet along its western side 

(Thor Karlstrom, unpub. data, 

1964; George Plafker, unpub. 

data, 1965). 

ments along previous faults also 

may have contributed to the avalanche activity in the Eklutna area 

and to the distribution of ground 

cracks along the west shore of 

Cook Inlet in line with the Lake 

Clark-Castle Mountain fault. 

The distribution of ground 

breakage in the 1964 earthquake 

indicates that in the lowlands of 

the Cook Inlet area the most damage from future seismic activity 

can be expected on outwash deltas, 

lowland areas underlain by thick 

marine or lake silt, and in alluvium 

and outwash along the larger 

streams. 

Plafker, George, 1965, Tectonic deformation associated with the 1964 

Alaska earthquake: Science, v. 148, 

no.3678,p.1675-1687. 

Small, J. B., 1966, Alaskan surveys to 

determine crustal movement ; Pt. 1, 

vertical bench mark displacement : 

U.S. Coast and Geodetic Survey, 24 p. 

U.S. Coast and Geodetic Survey, Wood, 

F. G., ed.-in-chief, 1966, The Prince 

William Sound, Alaska, earthquake 

of 1964 and aftershocks, VI: U.S. 

Coast and Geodetic Survey Publication 10-3, 263 p. 

Waller, R. M., 1966, Effects of the earthquake of March 27, 1964, in the 

Homer area, Alaska, with a section on 

Beach changes on Homer Spit by Kirk 

M. Stanley: U.S. Geol. Survey Prof. 

Paper 542-D, p. D1-D28. 

-U.S. GOVERNMENT PRINTING OFFICE: 1967 Q-262-870