Effects on Communities 

·1 ~ 

(J 

Anchorage 

G EOLOGICAL SURVEY PROFESSIONAL PAPER 542-A 
This page intentionally left blank
The Alaska Earthquake 

March 27, 1964: 

Effects on Communities 

This volume was published as separate 

chapters A-G 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 542 
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary 

GEOLOGICAL SURVEY 

William T. Pecora, Director 

7 2 3 6 5 6 :5 0 9 9

'

1 
CONTENTS 

[Letters designate the separately published c~ters] 

(A) Effects of the earthquake of March 27, 1964, at Anchora-ge, Alaska, by 

Wallace R. Hansen. 

(B) Effects of the earthquake of March 27, 1964, at Whittier, Alaska, by Reuben 

Kachadoorian. 

(C) Effects of the earthquake of March 27, 1964, at Valdez, Alaska, by Henry 

W. Coulter and Ralph R. Migliaccio. 

(D) Effects of the earthquake of March 27, 1964, in the Homer area, Alaska, by 

Roger M. Waller, with a section on Bea:ch changes on Homer Spit, .by Kirk 

W. Stanley. 

(E) Effects of the earthquake of March 27, 1964, at Seward, Alaska, by Richard 

W.Lemke. 

(F) Effects of the earthquake of March 27, 1964, on the communities of Kodiak 

·and nearby islands, by Reuben Kachadoorian and George Plafker. 

(G) Effects of the earthquake of March 27, 1964, on various communities, by 

George Plafker, Reuben Kachadoorian, Edwin B. Eckel, and Lawrence R. 

Mayo. 

·U.S. GOVERNMENT PRINTING OFFICE: 1969 o-312-357 
THE ALASKA EARTHQUAKE, MARCH 27, 1964- 

EFFECTS ON COMMUNITIES 

Effects of the Earthquake 

Of March 27,1964 

At Anchorage, Alaska 

BY WALLACE R. HANSEN 

A description and analysis of the damage resulting from seismic vibration, ground cracks, and 

especially landslides in Alaska's largest city 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 542-A 

783-132 CL-65---1 
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary 

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1965 

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

Washington, D.C. 20402 
Page 

Abstmct ____ ----- _ __ _ _ _ _ __ _ _ _ A1 

Introduction__________________ 2 

Acknowledgments_________ 2 

The earthquake and its immod~ate aftermath_______ 2 

Geologic.setting__ _ _ _ _ _ _ _ _ _ 11 

Bootlegger Cove Clay__________ 12 

Physical properties________ 13 

Shear strength________ 13 

Sensitivity___________ 14 

Atterberg limits_______ 15 

Vibration tests________ 17 

Pulsating-load tests____ 17 

Specific gravity_______ 18 

Physico-chemical tests_____ 19 

Mineralogy_--____________ 19 

Depositional environment__ 20 

l~arthquake effects____________ 21 

Direct seismic effects _____ - 21 

Alaska Psychiatric Institute_______________ 23 

The Alaska Railroad 

marshalling yards___ 23 

Alaska Sales and Service Building _____ 7 _ _ 23 

Anchorage International 

Airport_ _ _ _ _ _ _ _ _ _ _ _ 23 

Anchorage Westward 

HoteL-_______ _ _ _ _ _ 23 

Cordova Building_____ 24 

Elemendorf Air Force 

Base_______________ 24 

CONTENTS 

Earthquake effects-Continued 

Direct seismic effects-Con. Page 

Fifth A venue Chrysler 

Center_____________ A24 

First Federal Savings 

and Loan Building___ 24 

Four Seasons Apartment 

Building ___________ 24 

Hill Building_________ 25 

Hillside Apartments___ 25 

Knik Arms Apartment 

Building___________ 26 

Mount McKinley Building and 1200 L Street 

Apartment Building_ 26 

Penney's Department 

Store Building______ 26 

Port of Anchorage area_ 27 

West Anchorage High 

School_____________ 27 

Ground displacements other 

than landslides _______ ~__ 27 

Ground cracks and·com-

. paction_ _ _ _ _ _ _ _ _ _ _ _ 2 7 

Sand boils and mud 

fountains___________ 29 

Landslides ________________ 30 

Debris slides, avalanches, 

and rotational slides__ 30 

Slides along Turnagain Arm______ 30 

ILLUSTRATIONS 

PLATES 

[Plates are in pocket] 

1. Map of Turnagain Heights landslide. 

Earthquake effects-Continue:! 

Landslides-Continued Page 

Debris slides, etc.-Con. 

Potter Hill slides__ A31 

Slides at Point 

Woronzof_______ 33 

Slides near Cairn 

Point __________ 33 

Slides on west side 

of Knik Arm____ · 34 

Rotational slides 

along Bluff 

Road__________ 36 

Translatory slides_____ 38 

Geologic setting___ 38 

Geometry and 

mode of failure__ 40 

. The graben rule___ 41 

Individual translatory landslides_ 41 

Fourth A venue 

slide_______ 41 

L Street slide__ 43 

Native Hospital slide___ 49 

Government · 

Hill slide_ _ _ 53 

Turnagain 

Heights 

slide_______ 59 

Landsliding prior to the March 27 

ear-thquake--~-------------- 66 

References_____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 6 7 

2. Geologic map and section through part of. Turnagain Heights landslide. 

FIGURES 

Page Page Page 

1. Map of Anchorage, Alaska, 3. Wreckage of Government 5. Wreckage of Penney's depart- and vicinity ____________ _ A3 Hill SchooL ____________ _ A6 ment store ___ ----------- A9 

2. Trace made by dresser leg on 4. View west along Fourth 6. Damage to yards of the 

tile flooring ____________ _ 5 Avenue __ · ______________ _ 8 Alaska Railroad ____ - - - - - 10 

m 
IV 

7. Wreckage of control tower at 

Anchorage International 

Airport ____ - _ - _____ - - - - -

8. Summary of torsional vane shear strengths _________ _ 

9. Plasticity charts __________ _ 

10. Statistical liquid-limit distribution curves __________ _ 

11. Liquid-limit sensitivity distribution curves ______ -_-

12. Relation between sensitivity 

and liquidity index ______ _ 

13. Wreckage of six-story Four 

Seasons Apartment Build- ing ____________________ _ 

14. Sketch map showing ground 

cracks, Port of Anchorage 

and· vicinity ____________ _ 

15. Part of a sand boiL _______ _ 

16. Diagrammatic section near Point Campbe1l _________ _ 

17. Map and profile of Potter 

Hill landslide _______ -_---

18. Photogeologic sketch map of 

Point Woronzof landslide_ 

19. Rotational slump near 

Sleeper landing strip ____ _ 

Page 

All 

14 

15 

16 

17 

18 

25 

28 

29 

30 

32 

33 

34 

CONTENTS 

20. Block diagram of compound 

slump near Sleeper landing 

strip __________________ _ 

21. Chaotic pressure ridge at toe 

of rotational slide, Bluff 

Road __________________ _ 

22. Sketch section through rotational slide at Bluff Road __ 

23. Slope stability chart _______ _ 

24. Block diagram of a translatory slide ______________ _ 

25. Map of Fourth Avenue landslide area ______________ _ 

26. Sharp-crested pressure ridge 

at Second A venue and C 

Street, Anchorage ____ _: __ _ 

27. Map of L Street slide area __ 

28. Wrecked dwelling astride 

bounding fracture, L Street 

graben at Eighth Avenue 

and N Street ___________ _ 

29. House pushed off foundation 

by pressure ridge _______ _ 

30. Geologic sections through 

the L Street slide _______ _ 

31. Map of Native Hospital slide __________________ _ 

TABLES 

Page 

A35 

36 

37 

39 

40 

42 

44 

45 

46 

47 

48 

50 

32. Air view of Native Hospital slide __________________ _ 

33. Geologic sections through the 

Native Hospital slide ____ _ 

34. Overthrust toe of Native 

Hospital slide __________ _ 

35. Air view of Government Hill 

slide __________________ _ 

36. Wreckage of Government 

Hill SchooL ____________ _ 

37. Geologic section through 

Government Hill slide ___ _ 

38. Map of Government Hill 

slide __________________ _ 

39. Homes devastated by Turnagain Heights slide ______ _ 

40. Tree trunk split by tension 

fracture _______________ _ 

41. Furrowed, slickensided clay 

ridge, Turnagain Heights slide __________________ _ 

42. Sharp-crested clay ridge, 

Tu:·nagain Heights slide __ 

43. Slip surface of Turnagain 

Heights slide ___________ _ 

44. Sketch section through eastern part of Turnagain 

Heights slide ___________ _ 

1. Foraminifera from Bootlegger Cove Clay, Anchorage, Alaska, boring Page 

A120 A--------------------------------------------------------------- A21 

2. Foraminifera from Bootlegger Cove Clay, Anchora·ge, Alaska, borings 

A110A and B-----------------------------~--------------------------- A21 

Page 

A51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

61 

63 

65 
THE ALASKA EARTHQUAKE, MARCH 27, 196EFFECTS ON COMMUNITIES 

EFFECTS OF THE EARTHQUAKE OF MARCH 27,1964, AT 

ANCHORAGE, ALASKA 

Anchorage, Alaska's largest city, is 

about 80 miles west-northwest of the 

epicenter of the March 27 earthquake. 

Because of its size, Anchorage bore the 

brunt of property damage frm the 

quake ; it sustained greater losses than 

all the rest of Alaska combined. Damage was caused by direct seismic vibration, by ground cracks, and by landslides. Direct seismic vibration 'affected chiefly multistory buildings and 

buildings having large floor areas, probably because of the long period and large 

amplitude of the seismic waves reaching Anchorage. Most small buildings 

were spared. Ground cracks caused 

capricious damage throughout the Anchorage Lowland. Cracking was mast 

prevalent near the heads or within landslides but was also widespread dsewhere. Landslides themselves caused 

the most devastating damage. 

Triggering of landslides by the earthquake was related to the physicalengineering properties of the Bootlegger 

Cove Clay, a glacial estuarine-marine 

deposit that underltes much of the Anchorage area. The Bootlegger Cove 

Clay contains zones of low shear 

strength, high water content, and high 

sensitivity that failed under the vibratory stress of the eafiquake. Shear 

strength in sensitive zones ranged frm 

less than 0.2 tsf to about 0.5 tsf; sensitivity ranged from about 10 to more 

than 40. Sensitive zones generally are 

By Wallace R. Hansen 

ABSTRACT 

centered about 10 to 20 feet above sea 

level, between zones of stiff insensitive 

clay. Many physical tests by the U.S. 

Army Corps of Engineers were ctirected 

toward analyzing the causes of failure 

in the Bootlegger Cove Clay and finding 

possible remedies. Strengths and sensitivities were measured directly in the 

field by means of vane shear apparatus. 

A4tterberg limits, natural water contents, triaxial shear, sensitivity, dynamic modulus, cmsolidation strength, 

and other properties were measured in 

the laboratory. Pulsating-load tests 

simulated earthquake loading. 

Most of the destructive landslides in 

the Anchorage area moved primarily by 

translation rather than by rotation. 

Thus, all the highly damaging slides 

were of a single structural dynamic 

family despite wide variations in size, 

appearance, and complexity. They slid 

on nearly horizontal slip surfaces after 

loss of strength in the Bootlegger Core 

Clay. Same failures are attributed to 

spontaneous liquefaction of sand layers. 

All translatory slides surmounted flattopped bluffs bounded marginally by 

steep slopes facing lower ground. Destructive translatory slides occurred in 

the downtown area (Fourth Avenue 

slide and L Street slide), at Government Hill, and at Turnagain Heights. 

Less destructive slides occurred in many 

other places-mostly uninhabited or 

undeveloped areas. 

In most translatory slides, damage 

was greatest in graben areas at the 

head and in pressure-ridge areas at the 

toe. Many buildings inside the perimeters of slide blocks were little damaged 

despite horizontal translations of several feet. The large Turnagain Heights 

slide, however, was characterized by a 

complete disintegration and drastic 

lowering of the prequake land surface. 

Extensive damage back from the slide, 

moreover, was caused by countless tension cracks. 

An approximation of the depth of 

failure in the Bootlegger Cove Clay in 

the various slides may be obtained by 

using a geometric relationship herein 

called the "graben rule." Because the 

cross-sectional area of the graben at the 

head of the slide approximated the 

cross-sectional area of the space voided 

behind the slide block as the block 

moved outward, the depth of failure 

was equal to the area of the graben 

divided by the lateral displacement. 

This approximation supplements and 

accords with test data obtained from 

borings. The graben rule should apply 

to any translatory slide in whi& flowage of material from the zone of failure 

has not been excessive. 

Geologic evidence indicates that landslides similar to those triggered by the 

March 27 earthquake have occurred in 

the Anchorage area at variouaj times in 

the past 
A2 ALASKA EARTHQUAKE, MARCH 27, 1964 

INTRODUCTION 

Anchorage, "metropolis of the 

north" and Alaska's largest city, 

is the rapidly expanding commercial center of the 49th State. Anchorage is about 80 miles westnorthwest of the epicenter of the 

March 27 earthquake (fig. 1). 

The Anchorage Lowland, a 

broad, undulatory glacial plain on 

which the greater Anchorage area 

is situated, is roughly triangular. 

It is bounded on the northwest by 

Knik Arm of Cook Inlet, on the 

southwest by Turnaga'ln Arm, and 

on the east by the tcbrupt west 

front of the Chugach Mountains. 

Anchorage itself is crowded close 

to Knik Arm, but its perimeter is 

moving east and south because of 

suburban growth and soon, no 

doubt, will reach Turnagain Arm. 

Expansion north and northeast toward the Eagle River, along the 

narrow corridor between the mountains and Knik Arm, is largely 

checked by the military reservations of Fort Richardson and 

Elmendorf Ah- Force Base. 

ACKNOWLEDGMENTS 

Many ideas and conclusions pmsented in this report were reached 

in concert with R. D. Miller and 

C. A. Kaye, both of whom shortly 

after the March 27 earthquake 

joined the author in field investigations at Anchorage. Most of the 

credit for devising the "graben 

rule" (see p. A41) must go to 

Kaye. Discussions with M. G. Bonilla, Ernest Dobrovolny, E. B. 

Eckel, Reuben Kachadmrian, D. 

S. McCullach, and Roger M. Waller mnsciously or unconsciously led 

to thoughts incorporated into this 

report. J. R. Helm, A. B. Dodd, 

and Arthur Gervais of the Topographic Division, U.S. Geological 

Survey, ran control for profiles of 

the various landslides. Helm also 

prepared the topographic maps of 

the Native Hospital, Government 

Hill, and Turnagain Heights 

slides, using a Wild B-8 plotter. 

Special thanks are duo the U.S. 

Army Corps of Engineers for the 

materials and information that 

they supplied. A report prepared 

for the Corps by Shannon and 

Wilson, Inc. (1964) has been 

freely utilized, and several of its 

illustrations are reproduced herein. The Engineering Geology 

Evaluation Group (see p. AlO) , an 

ad hoc organization that carried 

out early investigations at Anchorage at a critical time immediately after the earthquake, is also 

thanked for its free release of otherwise unobtainable information. 

THE EARTHQUAKE AND 

ITS IMMEDIATE AFTERMATH 

At 5:36 p.m. on Good Friday, 

March 27,1964, Anchorage and all 

southern Alaska within a radius 

of about 400 miles of Prince William Sound were struck by perhaps 

the strongest earthquake to have 

hit North America within historic 

time. The magnitude of this 

great quake has been computed by 

the U.S. 'Coast and Geodetic Survey at 8.5 on the revised Richter 

scale. Its epicenter was about 80 

miles east-southeast of Anchorage 

near the head of Prince William 

Sound. Reportedly, the quake 

was felt throughout most of 

Alaska, including such remote 

points as Cape Lisburne, Point 

Hope, Barrow, and Umiat, 600 to 

800 miles north of the epicenter on 

the Arctic Slope of Alaska, and 

at Fort Randell, 800 miles southwest at the tip of the Abska peninsula. 

Eyewitness accounts of happenings at Anchorage during and immediately after the earthquake 

have been reported in many publications, both technical and popular. Much valuable inforrn~tion 

has thus been gained from the objective observations of individuals 

who were equal to the task. Calm 

detachment under such trying circumstances plainly is a rare and 

admired virtue. Some confusion 

and contradiction did appear in 

early accounts, not surprisingly, in 

view of the distressing conditions 

under which the observations were 

made. 

The duration of the earthquake at Anchorage can only be 

surmised owing to the lack of 

strong-motion seismograph records. Although seismographs 

have since been installed, none was 

present in Southern Alaska at the 

time of the quake. Intense seismic 

motions seem to have lasted 3 to 4 

minutes, possibly longer. Where 

localized ground displacements 

occurred, as in or near landslides, 

strong motions may have lasted 

appreciably longer, after strong 

seismic shaking had ceased. According to Shannon and Wilson 

Inc. (1964, p. 11) , the durations 

at Anchorage, timed on wrist or 

pocket watches, by several eyewitnesses whom they consider reliable, ranged from 4 minutes 25 

seconds to 7 minutes. Even longer 

durations were reported outside 

the Anchorage area. Steinbrugge 

(1964, p. 62) noted that persons at 

Anchorage were able to accomplish several time-consuming tasks 

during the shaking, including such 

things as leaving and reentering 

buildings more than once, or helping other individuals to escape, despite much difficulty in standing 

and walking. In some areas, however, people reportedly were 

thrown to the ground by the force 
EFFECTS AT ANCHORAGE A3 

1.-Map of Anchorage, Alaska, and vicinity showing locations of major landslides and ground cracks, much generalized. 

783-132 0 - 65 - 2 
A4 ALASKA EARTHQUAKE, MARCH 27, 1964 

of the acceleration and were unable to regain their footing. 

There seems to be general agreement that the first waves to arrive at Anchorage had strong eastwest components of movement. 

Objects reportedly were thrown 

from shelves and cupboards on 

east and west sides of rooms, and 

some individuals were said to have 

been propelled bodily across rooms 

in those directions. Figure 2 

shows the trace on an asphalt tile 

floor made by a dresser leg. Because the epicenter was east of 

Anchorage, an east-west ground 

motion was expectable. As the 

shaking continued, however, the 

motion is said to have shifted to 

north-south, and tall buildings 

that had first rocked to-and-fro 

east and west began to rock north 

and south as well, in a complex combination of movements. 

Strain-fracture patterns in the 

walls of multistory buildings at 

Anchorage seem to bear out such 

observations. North-south components of motion, moreover, are 

theoretically plausible, especially 

in view of the severe tectonic readjustments southeast and south of 

Anchorage in the Prince William 

Sound and Kodiak Island areas. 

The earthquake seems to have resulted from the rupture of rock at 

depth beneath a very broad area, 

extending from some point near 

the epicenter southwest to the 

south tip of Kodiak Island (U.S. 

Coast and Geodetic Survey, 1964, 

p. 31; Grantz and others, 1964, p. 

2) ; the arrival of seismic waves at 

Anchorage from such a broad 

source must have caused a very 

complex ground motion (fig. 2). 

Total earthquake damage to 

property in the Anchorage area 

has not been fully evaluated and 

perhaps will never be fully known. 

Nine lives are reported to have 

been lostfive in the downtown 

area, three at Turnagain Heights, 

and one at the International Airport. In less than 5 minutes, more 

than 2,000 people, including apartment dwellers, were made homeless, according to press estimates. 

The loss of life was less in Anchorage than in some of the small 

coastal towns, where many people 

were killed by sea waves. But 

Anchorage, because of its much 

greater size, bore the brunt of the 

property damage and property 

losses reportedly were greater 

there than in all the rest of Alaska 

combined. 

Early estimates by the Office of 

Emergency Planning indicated 

that about 75 percent of the City's 

total developed worth was measurably damaged. Early estimates of 

total damage, however, tended to 

be larger than later ones. According to the Anchorage Daily Times 

of April 9, 1964, 215 homes were 

destroyed in Anchorage and 157 

commercial buildings were destroyed or damaged beyond repair 

(Grantz, Plafker, and Kachadoorian, 1964, p. 14). At Turnagain 

Heights alone, 75 or more dwellings were destroyed. Estimates 

by the Daily Times placed the 

damage at about $200 million. 

Later, the Office of Emergency 

Planning estimated the total damage to Alaska at about $537,600,- 

000, of which about 60 percent was 

sustained by the Anchorage area 

(National Board of Fire Underwriters and Pacific Fire Rating 

Bureau, 1964, p. 5). The final total 

damage estimate for Alaska, exclusive of personal property and 

loss of income, was about $311 million (Federal Reconstruction and 

Development Planning Commission for Alaska, 1964, p. 11). 

Scores of buildings throughout 

Anchorage sustained damage requiring repairs costing many 

thousands of dollars. 

The school system was hard hit. 

Early estimates of damage came, t~ 

about $3.86 million. Classes were 

not in session, fortunately, so the 

buildings were empty. Twenty of 

the 26 schools in Anchorage were 

soon back in operation. West 

Anchorage High School, however, 

was severely damaged by seismic 

vibration. G o v e r n m e n t Hill 

Grade School, astride a landslide 

(fig. 3), was nearly a total loss, 

although plans have been made to 

salvage an intact part of the building outside the slide for use other 

than as a school. Denali Grade 

School was damaged by ground 

cracks and was closed indefinitely, 

pending damage evaluation and 

repair. 

In downtown Anchorage (the L 

Street and Fourth Avenue landslide areas), about 30 blocks of 

dwellings and commercial buildings were destroyed or ceverely 

damaged (fig. 4). A new six-story 

apartment building, the Four Seasons, was razed. A new five-story 

department store (J. C. Penney 

Co.) was damaged beyond repair 

by seismic shaking and had to be 

torn down (fig. 5). Many automobiles in the downtown area were 

struck by falling debris. Twin 14- 

story apartment buildings, though 

a mile apart, sustained massive, 

nearly identical vibratory damage, 

much of it in response to vertical 

shearing forces caused by oscillation. Many other multistory or 

large-area buildings were severely 

damaged. 

Water mains and gas, sewer, telephone, and electric systems were 

disrupted (Waller, Thomas, and 

Vorhis, 1965, p. 126). Total damage to utilities has been estimated 

at about $15 million (Alaskan 

Construction Consultants Committee, 1964, p. 11). Providentially, 

electric power failed at the very 

onset of the quake. Although the 

loss of power might seem to be an 

added hardship to the stricken 

city, untold numbers of fires were 
EFFECTS AT ANCHORAGE A5 

NORTH 

2.-Horizontal trace on asphalt tile flooring left by dresser leg during earthquake. Net movement of dresser was about N. 

75" W. Other legs left nearly identical traces. Sundry items on dresser tops were little disturbed. Trace reproduced by 

Oliver V. Kola, published by permission of Dr. M. A. Sozen. Scale of trace, X 4/2. 
1 3.-Wreckage of Government Hill School. The south wing of the building, shown here, collapsed into a graben at th 
head of the slide. Set slip of the graben block is shown by the displacement of the roofline. Photograph by M. G. Bonilla. 
A8 ALASKA EARTHQUAKE, MARCH 2 7, 19 64 

4.-View west along Fourth Avenue at head of landslide. North (right) side of street has collapsed into a graben. Vertical 

displacement is about 10 feet. Photograph by Mac's Foto, Anchorage, Alaska. 

probably avoided because of the 

lack of electric current in all the 

severed wiresand at a time, too, 

when water was unavailable for 

fighting fire. The destruction of 

San Francisco by fire on the heels 

of the earthquake of 1906 is forcefully recalled. Fukui, Japan, was 

similarly destroyed in 1948. Anchorage spent the night of March 

27 in total darkness, but the city 

had no fires and mas prepared to 

deal with the many disrupted electric circuits when service was restored. 

Roads and railroad facilities 

mere badly damaged. In the 

(10x1--nto\vn area, many streets were 

blocked by debris, and in landslide areas, streets and roads Irere 

conll~letely disrupted. Differential settlelnent caused marginal 

cracking along scores of highway 

fills througl~out the Anchorage 

TAo~vland. I11 The Alaska Railroad yards 3%-here landslide debris 

spread across trackage and damaged or destroyed maintenance 

sheds (fig. 6), an estimated $2,370,- 

700 damage ~vas sustained (Alaskan Construction Consultants 

Committee, 1964, p. '74). Cars and 

equipment were overturned, and 

car shops were damaged by vibration. Along the main line of the 

railroad, bridges failed, fills settled, and tracks were bent or 

buckled; at Potter, near the south 

margin of the Anchorage LOTland, several hundred feet of track 

was carried away in an area that 

has had a long history of repeaid 

sliding. 

At the Anchorage International 

Airport, the control tower failed 

under seismic vibration and collapsed to the ground (fig. 7), killing one occupant and injuring 

another. The airport terminal 

building, although tied structurally to the tower, was only slightly 
EFFECTS AT ANCHORAGE A9 

5.-Wreckage of Penney's department store, Fifth Avenue and D Street, Anchorage. Building failed after sustained seismic 

shaking. Most of rubble has been cleared from streets. Photograph by George Plafker. 

damaged except where it adjoined 

the tower. A near'by Post Office 

building was damaged a moderate 

amount (Berg and Stratta, 1964, 

p. 14). Almost 20,000 barrels of 

aviation fuel mas lost from 

a ruptured storage tank. Run- 

.ways and taxiways were slightly 

damaged but not put out of commission; air traffic was temporarily controlled first from a parked 

aircraft and then from a tower at 

the nearby Hood Lake landing 

strip (Federal Reconstruction and 

Development Planning Commission for Alaska, 1964, p. 25). 

Facilities at the Port of Anchorage were damaged by seismic vibration and ground cracks. Four 

cranes jumped their tracks and in 

so doing, damaged their undercarriages and counterweight arms 

(Berg and Stratta, 1964, p. 44 and 

47). Two steel storage tanks were 

toppled and destroyed. Nearby 

oil-storage tanks were damaged 

superficially, but large quantities 

of fuel oil were lost. An expected 

seismic sea wave fortunately did 

not materialize. 

Landslides caused the greatest 

devastation in the Ilncl~orage area. 

Great slides occurred in the downtown business section (Fourth 

,l\-enue slide), in the lev-er downto1v11 business and residential area 

(I, Street slide), at Government 

Hill, and at Turi~apain Heights. 

Less devastating slides occurred in 

undeveloped or unpopulated areas 

near the Alaskan Satire Service 

Hospital, at Romig Hill, at the 

Alaska H i g h w a y Department 

garage, at Bluff Road near the 

U.S. Army Corps of Engineers 

Headquarters Building, on the 

west bluff of Government Hill, at 

Point IVoronzof, Point Campbell, 

Cairn Point, and on the west side 

of Knik Arm near Sleeper landing 

strip in an uninhabited area recently opened to homesteading. 

The slide at Potter has already 

been mentioned. 

Capricious damage was caused 

by ground cracks. Such damage 

vas mostly localized, and many 

areas were spared. Cracking was 

inost common behind the heads 

of landslides, but it was also prevalent throughout the lowland in 

areas underlain by clay or silt or 

artificial fills on muskeg. Differential compaction was a common cause. Cracking was minimal in areas of thick ground 

moraine. 

The flow of streams, such as 

Ship Creek and Chester Creek, was 

greatly reduced, temporarily, by 

percolation of water into cracks. 

Gages in water wells recorded 
6.-Damage to yards of The Alaska Railroad, looking northwest, caused by earthflow 

undamaged wa,ter tank in background. 

marked fluctuat.ions, not just in 

Anchorage and southeast Alaska, 

but at places as distant as Georgia, 

Florida, and Puerto Rico (Waller 

and others, 1965, p. 126, 131). 

For a city of its size, Anchorage 

has in residence a large contingent 

of geologists and other earth scientists. Within hours after the 

quake, many of these individuals 

had begun independent investigations of the location, severity, nature, and causes of earthquake 

damage. On March 29, 2 days 

after the earthquake, a small group 

of geologists under the leadership 

at toe of Government Hill slide. Note 

of Dr. Lidja Selkregg of the 

Alaska State Housing Authority 

was commissioned by the housing 

authority and the city of Anchorage to outline "necessary and immediate courses of action" to be 

taken by the city. This group became known as the Engineer- 
EFFECTS AT ANCHORAGE All 

7.-Wreckage of control tower at Anchorage International Airport. Six-story tower 

Photograph by George Plafker. 

The work of the Engineering 

Geology Evaluation Group deserves high praise. Its preliminary findings and recommendations were completed on April 12, 

1964,2 weeks after the earthquake, 

and a final report was completed 

on May 8,1964. The findings and 

conclusions of the group provided 

the basis for many subsequent investigations by other agencies. 

Xuch of the information presented 

by this paper has been derived 

from the work of this group. 

ing Geology Evaluation Group 

(Schmidt, 1964, p. 13). Its mem1 bership rose to 40 after a call was 

I made for technical help. I 

GEOLOGIC SETTING 

I 

Anchorage is near the east 

border of a deep structural trough 

filled with moderately consolidated 

Tertiary rocks that underlie Cook 

Inlet and extend northeastward 

toward Mount McKinley at the 

head of the Susitna Lowland 

(Capps, 1916, 1940). At Anchorage, Tertiary rocks are covered by 

Pleistocene deposits, but they have 

been penetrated by drill holes. 

The group immediately began a 

program of mapping and data 

gathering. They contracted for 

aerial photography, started a drilling program in the major slide 

areas in cooperation with the Alaska Department of Highways, and 

ran standard laboratory tests on 

the various soil zones involved in 

the land failures. Drilling and 

soil testing were subsequently 

taken over and greatly expanded 

by the office of the U.S. Army District Engineer at the request of the 

failed under sustained seismic shaking. 

I city of Anchorage, under a contract dated 25 April 1964 between 

the District Engineer and Shannon 

and Wilson, Inc., soil mechanics 

and foundation engineers, Seattle, 

ITash. The Corps of Engineers 

meanwhile had immediately begun disaster relief. 

The Chugach Mountains just 

east of Anchorage consist chiefly 

of Mesozoic argillite and graywacke, variably deformed and 

metamorphosed, and intruded by 

small bodies of igneous rock 

(Capps, 1916, p. 153). The nature of the contact between the 

soft Tertiary rocks of the lowland and the harder Mesozoic rocks 

of the mountains has not been ascertained, owing partly to a lack 

of exposures and partly to a lack 

of study, but the very straight 

trace of the mountain front and 

the seeming truncation of structural trends by the mountain front 

suggest that the contact is a fault. 

On similar evidence, Karlstrom 

(1964, p. 21) inferred that the 

Icenai Mountain-a southward 

structural and topographic extension of the Chugach Mountainsare also bounded by a fault on the 

west. If these inferences are correct, a major structural displacement separates the Cook Inlet 
A12 ALASKA EARTHQUAKE, MARCH 27, 196 

Lowland from the bordering 

mountains. 

Cook Inlet and the Anchorage 

Lowland were occupied repeatedly by large piedmont glaciers in 

Pleistocene time (Karlstrom, 1957, 

1964; Miller and Dobrovolny, 

1959). Karlstrom has distinguished five major Pleistocene glacial advances in Cook Inlet, 

although not all reached the Anchorage arm. At the site of Anchorage, Pleistocene deposits 

briefly here. They consist chiefly 

of three categories of material : 

glacial till, deposited as ground 

moraine; proglacial sijty clays 

(including the Bootlegger Cove 

Clay) deposited in estuarine-marine or lacustrine-estuarine environments ; and fluvioglacial deposits of several types, but chiefly 

outwash sand and gravel. 

Most of Anchorage lies on late 

glacial (Naptowne-Wisconsin) 

outwash deposited in front of the 

to a of youngest Pleistocene glacier that 

feet or more. In general, these de- entered the area. This glacier con- pc~sits seem to thicken westward 

from the mountain front toward structed a large end moraine no&h 

Cook Inlet. They exerted a vital of the city at Elmendorf Air Force 

influence on the location and the Base (Miller and Dobrovolny, 

extent of earthcluake damage in 1959, P. 59). Remnants of the mo- u 

the Anchorage area. 

Because the Pleistocene deposits of the Anchorage arm have 

been described previously in considerable detail (Miller and Dobrovolny, 1959 ; Karlstrom, 1964 ; 

Cederstrom, Trainer, and Waller, 

1964), they will be described but 

raine are also preserved west of 

Knik Arm about 2% to 3 miles 

northeast of Point MacKenzie. 

Outwash sand and gravel from 

this glacier spread southward 

across the Anchorage Lowland 

and buried ground moraine and 

Bootlegger Cove ,Clay alike to 

depths as greak as 60 feet. In general, the outwash thins toward the 

west and south away from its 

source. It wedges out completely 

between Turnagain Heights and 

Point Woronzof. 

East of Anchorage along the 

foot of the Chugach Mountains, 

a massive lateral moraine was deposited by one or more of the preWisconsin glaciers that occupied 

the area (Miller and Dobrovolny, 

1959, p. 21). This moraine stands 

generally 1,000 to 1,200 feet above 

sea level and has a maximum altitude of about 1,400 feet. Bemuse 

the area commands impressive 

views across Cook Inlet toward the 

snow-swept Alaska Range and 

Mount McKinley, it has experienced a mild real estate boom, and 

the next few years should see extensive urbanization of its heights. 

The moraine fared well in the 

March 22' earthquake ; structures 

builh on it were little, if at all, 

distudbed. 

BOOTLEGGER COVE CLAY 

The Bootlegger Cove Clay has 

become renowned, since the March 

27 earthquake, for its part in the 

devastation. Most of the severe 

damage in the Anchorage area is 

traceable to failure within this formation, and an understanding of 

the mechanisms of landsliding in 

the Anchorage area requires some 

knowledge of its character and 

physical properties. Because of 

its critical relationship to the landsliding, it has been studied intensively since the earthquake, by the 

Corps of Engineers and by consultants to the corps. 

The Bootlegger Cove Clay was 

named and first described by 

Miller and Dobrovolny (1959, p. 

3548). In general the formation 

consists of three physically distinct but gradational zones-an 

upper and a lower stiff competent 

zone and a central weak sensitive 

zone. Failures occurred chiefly in 

the central zone. Waves generated by the earthquake led to a 

drastic loss of strength, a consequent failure of dynamically sensitive saturated sand, silt, and silty 

clay, and a resultant disruption of 

the ground surface by landsliding 

(Shannon and Wilson, Inc., 1964, 

p. 1-3). 

The Bootlegger Cove Clay underlies most of Anchorage and 

much of the adjacent area (Miller 

and Dobrovolny, 1959, pls. 3 and 

6; Trainer and Waller, 1965). 

Along Knik Arm, it is exposed 

almost continuously from a point 

about three-quarters of a mile east 

of Point Woronzof northward at 

least to the Eagle River. Just 

north of Anchorage, it passes beneath the Elmendorf Moraine. 

Toward the east and southeast, it 

laps across older glacial deposits 

and thins out against higher 

ground in the morainal belt at the 

base of the Chugach Mountains. 

South of Anchorage, it is continuous beneath a cover of sand and 

muskeg west from the SewardAnchorage Highway to the east 

base of the Point Woronzof-Point 

Campbell highland area and south 

to Turnagain Arm. It laps up 

and thins out against the delta1 

sand and gravel of the Point 
EFFECTS AT ANCHORAGE 

Woronzof-Point Campbell highland area. 

As described by Miller and 

Dobrovolny (1959, p. 39), the 

Bootlegger Cove Clay consists 

chiefly of silty clay, light gray 

(N7) when dry and dark greenish 

gray (5'GY 4/1) when wet. Very 

commonly the upper several inches 

to several feet immediately beneath the overlying outwash is oxidized to yellowis11 gray. The clay 

generally is delicately laminated 

in layers a fraction of a millimeter 

to several centimeters thick, although some intervals several feet 

thick are free of visible bedding. 

Throughout the clay are scattered 

layers of sand, some mere partings but others 25 feet or more 

thick. Such layers are lenticular 

and can only be traced short distances. In at least one landslide 

(Fourth Avenue), liquefaction of 

a sand layer is believed to have 

been the chief immediate cause of 

failure (Shannon and Wilson, 

Inc., 1964, p. 41). 

Scattered pebbles are present 

throughout the Bootlegger Cove 

Clay. Cobbles and boulders are 

present also but are rare. These 

stones contributed nothing to the 

failure of the clay and had no part 

in the Iandsliding, but they do indicate tlie periglacial environment 

in which the clay was deposited. 

Only ice rafting could have emplaced the larger boulders. Pebbles are most numerous in the 

lower part of the formation. On 

the west side of Knik Arm opposite Cairn Point, where the base 

of the formation is above tide water, the clay grades downward into 

stony till, seemingly without a 

clear-cut contact. 

Numerical designations refer to the RockColor Chart number (Goddard and others, 

1948). 

PHYSICAL PROPERTIES 

Soon after the earthquake, work 

started by the Engineering Geology Evaluation Group (1964) and 

later taken over by the U.S. Army 

Corps of Engineers (Shannon and 

Wilson, Inc., 1964) showed that 

the physical properties of the 

Bootlegger Cove Clay are far from 

uniform. Rather, a medial zone 

of low static shear strength and 

high sensitivity grades upward 

and do\\-nn-ard into stiffer nonsensitive zones. Sensitivity is defined as the ratio of undisturbed 

shear strength of a soil sample to 

remolded (kneaded or squeezed) 

shear strength of the same sample, 

regardless of the cause (Terzaghi 

and Peck, 1948, p. 33). 

Numerous physical tests by the 

Corps of Engineers-both in the 

field and in the laboratory-were 

made to analyze the causes of failure in the Bootlegger Cove Clay 

and find possible remedies. These 

tests are described in detail by 

Shannon and Wilson, Inc. (1964, 

p. 13-30) ; most of the information 

in the following paragraphs was 

abstracted f r o m their report. 

About 150 borings were drilled 

within and adjacent to the several 

landslide areas, either into or 

through the sensitive zone of the 

Bootlegger Cove Clay. Most borings were sampled at 5-foot intervals, and continuous samples were 

obtained at selected locations. Undisturbed samples were collected 

in 3- by 36- or 3- by 37-inch steel 

Shelby tubes. Five large-diameter "bucket auger" holes were 

drilled by the Corps for visual inspection of critical zones in the 

clay, for in-place shear-strength 

tests, and for carving out undisturbed samples by hand. Vaneshear tests in standard 3-inch holes 

were made at 12 locations in the 

Fourth Avenue, I, Street, and 

Turnagain Heights slide areas to 

measure in-place strengths and 

sensitivities of the clay. Similar 

tests were made on undisturbed 

samples both in the field and in 

the laboratory. In the laboratory, 

samples were also analyzed for Atterberg limits (see p. A14), natural-water content, triaxial shear, 

sensitivity, dynamic modulus, and 

consolidation strength. 

SHEAR STRENGTH 

Shear strength was measured 

in torsional-vane-shear tests, undrained triaxial tests, consolidated-undrained triaxial tests, and 

consolidated-drained triaxial tests ; 

strain, stress, volume change, and 

pore-water pressure were recorded 

throughout the tests (Shannon 

and Wilson, Inc., 1964, p. 28). 

The results of vane-shear tests for 

the Fourth Avenue and Turnagain 

Heights slide areas are shown in 

figure 8. Triaxial tests performed 

on the clay generally correlated 

well with the vane-shear tests 

within the ranges of strengths at 

which failure was prevalent. 

Tests correlated well in the range 

0.4 to 0.5 tsf (tons per square foot), 

but for clays of higher strength, 

tlie triaxial tests generally yielded 

somewhat higher values than the 

vane tests. Most of the samples 

of clay from critical depths in the 

landslides had i n i t i a 1 shear 

strengths between 0.2 and 0.7 tsf, 

and in this range the ratio of torsional-vane-shear-test results to 

triaxial-compression-test results is 

generally between 0.7 and 1.5 

(Shannon and Wilson, Inc., 1964, 

p. B8). This ratio indicates a 

fairly good correlation between 

test methods. In any event, the 

vane-shear-test results shown by 

the graphs of figure 8 clearly demonstrate the generally lower shear 

strength of the clay at intermediate depths as compared with shallower and deeper layers. 
ALASKA EARTHQUAKE, MARCH 27, 1964 

SHEAR STRENGTH, IN TONS PER SQUARE FOOT 

0 0.25 0.50 0.75 1.0 0 0.25 0.50 0.75 1 .O 

8.-Summary of torsional-vane-shear strengths of selected 

borings, Bootlegger Cove Clay, from Fourth Avenue slide area 

(left) and Turnagain Heights slide area (right). Simplified 

from Shannon and Wilson, Inc. (I%, pl. B15). 

Torsional-vane-shear apparatus 

was also used to measure the 

strength of the Bootlegger Cove 

Clay under sustained stress, because it was recognized that the 

duration of stress influences the 

resulting shear strength shown by 

the tested specimen (Shannon and 

Wilson, Inc., 1964, p. B7). At a 

given level (0.1 tsf), shear stress 

was applied for varying lengths 

of time. These tests showed that 

the Bootlegger Cove Clay loses 

shear strength as stress application 

is prolonged. In other words, the 

longer the stress is sustained, the 

lower the shear strengths. 

SENSITIVITY 

Sensitivity has previously been 

defined as the ratio of undisturbed 

shear strength to remolded sheaf 

strength. For example, a clay 

having ail undisturbed shear 

strength of 0.4 tsf and a remolded 

shear strength of 0.02 tsf has a 

sensitivity of 20. Sensitivies were 

measured by the Corps of Engineers on about 2,100 selected samples of the Bootlegger Cove Clay 

by means of field and laboratory 

vane-shear devices (Shannon and 

Wilson, Inc., 1964, p. 27), and a 

record of sensitivities was plotted 

on the boring logs. Of the 2,100 

samples tested, 302, or 14 percent, 

had sensitivities greater than 10; 

125, or 6 percent, had sensitivities 

greater than 20; 40, or 1.9 percent, 

had sensitivities greater than 30; 

and 11, or 0.5 percent, had sensitivities greater than 40. The 

highest sensitivity measured was 

60. 

The sensitive zone generally 

ranges in thickness from about 20 

to 30 feet, but it is as much as 40 

feet thick in some places and is 

nonexistent in others. In most 

places the center of the sensitive 

zone is above sea level, generally 

10 to 20 feet above, but in parts of 

the Turnagain Heights area it is 

below sea level. At no place has 
EFFECTS AT ANCHO'RAGE A15 

sensitive clay been observed higher 

than about 50 feet above sea level 

or lower than about 30 feet below 

sea level. Laboratory tests by the 

Corps indicate that the shear 

strength of the sensitive clay 

ranges from less than 0.15 to about 

0.40 tsf, and the sensitivity ranges 

from about 25 to as high as 60. 

The maximum shear strengths of 

the stiffer clays exceed 1 tsf. 

ATTERBERG LIMITS 

In a laboratory analysis of finegrained cohesive soils, it is customary to perform tests that yield 

information on the plasticity of the 

soils. These tests include measurements of natural water content 

(Wn) liquid limit (LL) and 

plastic limit (PL). The liquid 

limit is the water content in percentage of dry weight at which the 

soil passes from the liquid state 

into the plastic state. Similarly, 

the plastic limit is the water content of the soil at the boundary 

between the plastic state and the 

solid state. These limits of coil-. 

sistency are defined by standardized test procedures and are known 

as the Atterberg limits (Terzaghi 

and Peck, 1948, p. 32-36). The 

numerical difference between the 

liquid limit and the plastic limit 

is called the plasticity index (PI). 

The plasticity index represents the 

range of moisture content within 

which the soil is plastic. Clayey 

soils thus have higher plasticity 

indices than nonclayey or silty 

soils because they remain plastic 

through a wider range of moisture 

content (Stokes and Varnes, 1955, 

p. 85, 110; U.S. Bureau of Reclamation, 1960, p. 8,28). 

The plasticity charts (fig. 9) 

show the statistical relationship of 

liquid limit to plasticity index of 

the Bootlegger Cove Clay in the 

Fourth Avenue and Turnagain 

Heights slide areas, as measured 

for the Corps of Engineers by 

10 20 30 40 50 

LIQUID LIMIT (11) 

ATTERBERG LIMITS 

Upper stiff clay 

Sensitive clay 

0 Lower stiff clay 

10 20 30 40 50 

LIQUID LIMIT (11) 

9.-Plasticity charts from selected borings, Bootlegger Cove Clay, Fourth Avenue 

and Turnagain Heights slide area. Reprinted from Shannon and Wilson, Inc. (1964, 

pl. B16). CL, inorganic clay of low to medium plasticity; ML, inorganic silts and 

very fine sand; OH, inorganic clay of high plasticity; MH, inorganic silt; OH, 

organic clay. 

Sllannon and 7Vilson, Inc. (1964). sitive clay. Differences between 

These charts s1101\* generally the upper stiff chy and the sensihigher plasticity indices and liquid tive clay are not obvious on these 

limits for the lo\\-er stiff clay than charts, but they are quite apparent 

for the upper stiff clay or the sen- on statistical liquid-limit distri- 
A16 ALASKA EARTHQUAKE, MARCH 27, 1964 

bution curves (fig. 10). 'Nearly all 

points plotted on the plasticity 

charts lie above the "A" line-the 

line which separtttes soils of high 

cohesion and low permeability 

above from soils of low cohesion 

and high permeability below 

(Casagrande, 1947, p. 801). 

The statistical liquid-limit distrlbuhion curves (fig. 10) show the 

distinctions )between the three 

zones of the Bootlegger Cove Clay 

in the Fourth Avenue and Turnagain Heights areas. These curves 

bring out the differences between 

the upper stiff zone and the sensitive zone, and also the higher liquid limit of the lower stiff zone. 

The statistical relationship of sensitivity to liquid limit is shown by 

figure 11. In general, about 80 

percent of the soil samples tested 

had liquid limits within the range 

of 22 to 48 percent, regardless of 

their vertical positicm in the formation. About 80 percent of the 

liquid limits of the sensitive clay 

range from 22 to 38 percent, and 

about 80 percent from the lower 

stiff clay range from 32 to 50 percent. As sensitivity incrmses, the 

upper limit of the liquid limit decreases. Most clay samples of 

sensitivities greater than 10 had 

liquid limits in the range of 20 to 

40 percent, and no sensitive-clay 

sample had a liquid limit above 

45 percent. For sensitivities 

greater than 40, the range of liquid limits was only 22 to 28 percent (Shannon and Wilson, Inc., 

1964, p. B11). Several samples 

analyzed had a natural-water content greater than their liquid 

limits. 

To relate the limit values of a 

soil to its natural-water content, 

the water-plasticity ratio, or liquidity index, is sometimes used 

(Casagrande and Fadum, 1944, p. 

341). This ratio is equal to the 

natural-water content of the soil 

minus the plastic limit divided by 

FOURTH AVENUE SLIDE AREA 

12 

0 

10 20 30 40 

LIQUID LIMIT (11) 

TURNAGAIN HEIGHTS SLIDE AREA 

12 

8 

4 IZ, 

0 L 12 

- z 

8 a 

2 

m 

E 4 

2 

P 

14 4 

e 

3 

a 

a 

4 

0 

LIQUID LIMIT (11) 

10.-Statistical liquid-limit distribution curves from selected borings, Bootlegger 

Cove Clay. Reprinted from Shannon and Wilson, Inc. (1964, pl. B16). 
EFFECTS AT ANCHORAGE 

LIQUID-LIMIT DISTRIBUTION FOR SAMPLES HAVING SENSITIVITY (S) 

>40 

Sum of all samples having sensitivity (S) > 10 equals 100 percent 

11.-Liquid-limit sensitivity distribution curves, Bootlegger Cove Clay. Reprinted from Shannon and Wilson, Inc. (1965, pl. B17). 

the liquid limit minus the plastic sensitivity, and high susceptibility 

limit; that is (Wn- PL)/(LL- to failure. 

P). For 'the Bootlegger Cove 

Clay, it was found that in most 

soils having a water-plasticity ratio greater than 1.0lthe liquid limit 

ranged from 20 to 40 percent, and 

in soils having a water-plasticity 

ratio greater than 2.0 the liquid 

limit lay in the range 19 to 27 percent. A direct correlation also 

was found between sensitivity and 

the water-plasticity ratio (Shannon and Wilson, Inc., 1964, p. B11, 

pl. B17; see fig. 12, next page). 

Thus in the Bootlegger Cove Clay 

a high water-plasticity ratio is related to low shear strength, high 

VIBRATION TESTS 

Representative samples of sand 

and clay from the various slides 

were subjected to vibration tests 

from which the dynamic Young's 

modulus and the dynamic shear 

modulus of elasticity could be computed. These tests were designed 

to simulate in part the vibratory 

effects of the earthquake on the 

sand and clay. The vibration apparatus, developed by Shannon 

and Wilson, Inc. (1964, p. E3), 

subjected a cylindrical specimen to 

a sinusoidal vibration in a longitudinal or torsional mode in such 

n way that the frequency corresponded to a state of resonance. 

Both longitudinal and torsional 

resonance frequencies increased as 

straight-line functions of increased confining pressure. 

The shear modulus of the sands 

was found to be dependent on the 

confining pressure. The shear 

modulus of the stiff clay was about 

5,000 psi (pounds per square inch), 

and that of the soft sensitive clay 

was about 1,500 psi (Shannon and 

Wilson, Inc., 1964, p. 28). In 

nearly all tests, the value of the 

shear modulus and of Young's 

modulus increased as straight-line 

functions of increased confining 

pressure. 

PULSATING-LOAD TESTS 

Pulsating-load tests on saturated 

fine silty sand and on undisturbed 

samples of silty clay and clayey silt 

were run for the Corps of Engineers by H. B. Seed and K. L. Lee 

of the University of California at 

Berkeley (in Shannon and Wilson, 

Inc., 1964). These tests demonstrated the susceptibility of the 

Bootlegger Cove Clay and associated sands to loss of strength under pulsating-load conditions such 

as would be induced by an earthquake. In other words, the shear 

strength of the samples was markedly less under pulsating-load conditions (simulating an earthquake), than under static load. 

Seed's apparatus was so designed that applied deviator (axial) stress could be increased and 

decreased in one direction or could 

be changed from vertical to horizontal during each stress cycle, 

and thus the direction of shear 

stress in the specimen could be reversed. The latter test is called a 

"stress-reversing test." 

Because it is not feasible to collect undisturbed sand samples, 

sand specimens were artificially 

deposited in water in the labora- 
A18 ALASKA EARTHQUAKE, MARCH 2 7, 1964 

stress-reversing conditions, the 0 I 1 I 1 I I 

level of failure was substantially 0.2 0.4 0.6 0.8 1 .o 1.2 1.4 1.6 1.8 

lower than under non-stress-re- LloulDln INDEX (11) 

tory under conditions that simu- 48 

versing conditions. Thus, under a 

non-stress-reversing p u 1 s a t i n g 

load at a frequency of 2 cycles per 

second, failure generally followed 

50 cycles of maximum stress of 80 

to 100 percent of the static undrained strength, after a gradual 

buildup of strain, whereas under 

stress-reversing conditions, failure 

occurred abruptly without prior 

significant strain after a maximum 

stress of only about 55 percent of 

the static undrained strength. 

The natural vibration of an earthlated natural sedimentation. The 

sand was then subjected to pressures comparable to the in-place 44 

overburden pressures of the natural environment, about 1.8 kg per 

12.-Relation between sensitivity and liquidity index (water-plasticity ratio), 

Bootlegger Cove Clay. Reprinted from Shannon and Wilson, Inc. (1964, pl. B17). 

. 

. 

quake, according to Seed, probably has a pulse form somewhere 

between the two types used in these 

laboratory tests. It is concluded, 

therefore, that under earthquake 

conditions, failure would occur at 

a stress level below the static undrained strength of the clay, that 

is, somewhere between the limits 

indicated by the two types of 

pulsating stress applied in the 

laboratory. 

SPECIFIC GRAVITY 

Specific gravity was measured 

by Shannon and Wilson, Inc. 

(1964, p. Bll-B12) on 26 test specimens from various depths at seven 

different slide areas. Of the specimens tested, 1 had a specific gravity of 2.67, but the other 25 ranged 

cm2. Under stress-reversing con- 40 

ditions, sand specimens showed / I I 

negligible strains, but they did 

show progressive increases in pore- 36 - 

water pressures with increasing 

numbers of stress cycles. Failure 

abruptly followed a sudden increase in pore-water pressure equal 

in magnitude to the applied confining pressure, accompanied by - 

large strains and complete lique- D 

t faction. Liquefaction followed 50 

cycles of pulsating deviator stress 

of about 0.5 kg per cm2 applied V) 

at a frequency of about 2 cycles per 

second. This stress level is only 

about 10 percent of the strength of . an identical specimen tested under 

static-loading conditions. 

Clay samples were found to fail 

at levels of pulsating deviator 

stress substantially lower than the 

undrained compressive strength. 

Undrained compressive strengths 

of the specimens tested ranged 

from about 0.4 to 1.8 kg per cm2, 1 

and sensitivities ranged from ! Note: Only test results of samples taken from borlngs In the - 

about 15 to 60. Moreover, under 

Fourth Avenue sllde area and Turnagaln Heights slide 

area havlng o sensltlvlty (S) In excess of 8 have been used 
EFFECTS AT ANCHO'RAGE 

from 2.71 to 2.82, the average being 2.78. No correlation between 

specific gravity and shear strength 

or sensitivity was apparent. 

PHYSICO-CHEMICAL TESTS 

Physico-chemical analyses of six 

samples were made for tlze Corps 

of Engineers by J. K. Mitchell (in 

Shannon and Wilson, Inc., 1964, 

p. 13). Four of the samples-two 

from Turnagqin Heights and two 

from the Fourth Avenue areawere cuts from core intervals that 

also were analyzed mineralogically. The other two samples came 

from the L Street slide. Each 

sample was tested for pH, salt 

content, conductivity, and baseexchange capacity. Values of pH 

ranged from 8.2 to 10.3. These 

relatively high base values, according to Mitchell, are "consistent 

with high sensitivity because of 

the tendency of a high pH to promote dispersion of remolded Samples" (in Shannoiz and Wilson, 

Inc., 1964, p. 13). 

The salt content of the samples, 

expressed in tenns of equivalent 

NaC1, ranged from 1.03 grams per 

liter to somewhat less than 6 grams 

per liter. "By way of comparison," Mitchell points out, "the salt 

content of sea water is about 34 

grams per liter. Thus if the Anchorage clays are of marine origin 

then the results of these tests would 

suggest that they have been 

leached of salt since their original 

deposition. Such leaching could 

be important in generating a high 

sensitivity and stable suspensions 

after remolding." In support of 

this view, a marine depositional 

environnlent of near normal salinity, at sample depths spanning the 

zone of landslide failure, is indicated by the microfaunal assemblages in the clay (Patsy J. Smith, 

written commun., 1964). The 

paleontology of the clay is discussed on page A20. 

In measuring electrical conductivity, Mitchell (in Shannon and 

Wilson, Inc., 1964, p. 14) found 

that remolded clay had consistently greater conductivity at all 

frequencies than undisturbed clay. 

Remolded clay generally also had 

a greater variation in conductivity 

as frequency was 1-aried. Mitchell 

attributed these differences to 

greater dispersion (parallelism of 

clay particles) and smaller average effective particle size in the 

remolded samples. 

Base-exchange capacities of tlze 

six samples studied by Mitchell 

ranged from 4.6 to 10.9 milliequivaleizts per 100 g of dry clay. Of 

the three cations determinedsodium, calcium, and magnesiunl-Mitchell found that calcium 

was the most abundant in solution 

in all but one sample. Sodium was 

next and magnesium was least 

abundant. This ratio also suggests 

that authigenic brine 11-as leached 

froln tlze clay by the action of 

ground water ; hence that leaching 

may hare been a cause of the sensitivity. 

MINERALOGY 

Not much mineralogic work has 

been done on the Bootlegger Cove 

Clay. Seven samples collected by 

Miller and Dobrovolny (1959, p. 

42-43) from four localities and 

from set-en different parts of the 

section were analyzed by X-ray 

diffraction in two fractions eachclay (<2p) and silt (2 to 74p). 

Both fractions of each sample contained quartz, feldspar, mica, and 

chlorite as the chief constituents. 

Some contained montmorillonite, 

mixed layered chlorite-montkorillonite, or mixed layered chloritemontmorillonite-hornblende (Miller and Dobrovolny, 1959, p. 42). 

Quartz predominated in most silt 

fractions, followed by feldspar, 

but it was subordinate in the clay 

fractions, in which chlorite predominated. These seven samples 

resembled, in composition and general proportions of minerals, samples of other silty clay collected 

from lake, estuarine, and till deposits of the same general vicinity 

but of different ages. Their compositions, therefore, pfobably reflect parent material more than 

diagenesis. 

A single clay ssrtniple collected at 

Turnagain Heights after the 

earthquake was found to contain 

chlorite, illite, quartz, and feldspar in its clay fraction (Grantz, 

Plafker, and Kachadoorian, 1964, 

p. 26). Its composition by size 

was 25 percent clay, 61 percent silt, 

and 14 percent fine sand. 

Samples of Bootlegger Cove 

Clay from four drill hoIes, two 

from the Fourth Avenue area and 

two from Turnagain Heights, 

were analyzed by X-ray, differential thermal, thermogravimetric, 

and petrographic means by T. S. 

Shevlin for the Corps of Engineers (Shannon and Wilson, Inc., 

1964, p. H3). Two of the samples 

were sensitive; two were stiff. 

Shevlin found that quartz predominated in all samples; its peak 

intensities (X-ray) were greater 

than any other mineral in all size 

fractions analyzed. Feldspar was 

present in finely divided form in 

a11 samples, and kaolinite, illite, 

and chlorite were also present. 

One of the stiff samples was gritty 

and much siltier than the others, 

but there was no consistent variation either in size or mineral content between the sensitive and the 

stiff samples. Shevlin's table 1 is 

reproduced in part at top of page 

20 to show the distribution of 

particle sizes. 
A20 ALASKA EARTHQUAKE, MARCH 27, 1964 

-- - 

Percent finer than particle size (microns) 

38110181412l 1 

I Samples prefixed with A are from Fourth Avenue area; samples prefixed with C are from Turnagain Heights 

DEPOSITIONAL ENVIRONMENT 

Recent paleontologic studies by 

Patsy J. Smith (written commun., 

1964) indicate that the Bootlegger 

Cove Clay is of marine origin 

throughout but that it was deposited in environments of variable salinity. The depositional 

environment bears on the origin 

and distribution of sensitivity in 

the clay. Clay deposited in saline 

waters tends to flocculate. Flocculation occurs when negative particle surfaces are attracted to positive particle edges by electrostatic 

forces (Lambe, 1958, p. 8; Rosenqvist, 1962, pl. 5; Meade, 1964, p. 

BPB5) ; flocculated clay in turn 

acquires sensitivity when the interparticle bond is destroyed, as 

when ground water leaches the cation and thereby diminishes the 

electrolyte concentration (Mitchell, 1956, p. 693). Such leaching 

is promoted when marine clay beds 

are elevated above sea level. According to Bjerrum (1954, p. 49; 

1955, p. 108), the reduced electrolyte concentration, by decreasing 

the activity of the clay minerals, 

leads to a lowering of the Atterberg limits, which in turn reduces 

the shear strength of the clay by 

as much as 30 percent. 

Until recently the depositional 

environment of the Bootlegger 

Cove Clay was in serious doubt, if 

not dispute (Miller and Dobrovolny, 1959, p. 44; Schmidt, 1963, 

p. 350; Karlstrom, 1964, p. 35; 

Cederstrom, Trainer, and Waller, 

1964, p. 30). A brief review of 

past thinking, therefore, seems 

warranted. The environment has 

been considered to have been lacustrine, estuarine, or marine, or some 

combination thereof. Marine organisms had been noted in the 

Bootlegger Cove Clay by several 

investigators, although some doubt 

had existed as to whether the specimens noted were in place or had 

been cast ashore by storm waves 

(Miller and Dobrovolny, 1959, 

p. 45). Trainer (in Miller and 

Dobrovolny, 1959, p. 45) found 

estuarine mollusks that he was convinced were in place. Schmidt 

(1963, p. 350) verified Trainer's 

find and added an abundant microfauna in confirmation. Miller 

and Dobrovolny (1959, p. 46) reasoned, that varvelike beds and 

laminations high in the clay near 

Cairn Point indicated probable 

fresh-water deposition, a view 

subsequently shared by Cederstrom, Trainer, and Waller (1964, 

p. 32) but on slightly different evidence-the presence of well-sorted 

interbedded sands. Karlstrom 

(1964, p. 38) expressed the opinion 

that "the Bootlegger Cove Clay 

records proglacial-lake sedimentation * * * with an intervening interval of marine deposition"-in 

other words, fresh-water deposits 

separated by salt-water deposits. 

Smith's conclusions (w r i t t en 

commun., 1964) are based on 

studies of microfossils from drill 

samples collected by the Corps of 

Engineers. These continuously 

cored samples afforded a chance 

not provided by surface exposures 

to examine the depositional environment of the clay from the top 

of the formation down through 

and below the sensitive zone. 

Smith concluded that the forrnation was marine throughout the interval studied but that the upper 

part was deposited in a deltaic environment of low variable salinity 

such as now exists in the Yukon 

and Kiskokwim deltas. Fossils 

from the lower part of the formation, including the sensitive zone, 

indicated a shallow (25k meters) 

marine environment probably of 

near-normal salinity. V e r t i c a 1 

variations in the depositional environment, as indicated by fossils, 

thus may provide an explanation 

for the zonal character of the sensitivity: the stiffer clays accumulated in water of low salinity and 

the more sensitive clays accumulated in waters of near-normal 

salinity. Since deposition, reduction of the brine concentration by 

leaching probably has altered the 

plasticity of the clay and increased 

the sensitivity. 

Fossils identified by Smith, and 

their r e l a t i v e abundance, are 

shown in tables 1 arid 2. 
EFFECTS AT ANCHORAGE A21 

TABLE 1.-Foraminifera from Bootkgger Cove Clay, Anohorage, Alaska, Shannon and Wilson, .lnc. (1964) boring A120 & 

[Abundances estimated: A, abundant; C, common; F, few; R, rare] 

TABLE 2.-Foraminifera from Bootlegger Cove Clay, Anchorage, Alaska, Shanmn and Wilson, Znc. (1964) boring~ A 110 

A and B 

[Abundances estimated: AA, very abundant: A, abundant; C, common; F, few: R, rare] 

Sample interval (feet) 

. Species 

Protel hidiumcf.orbfculare(Brady) -.-.---.-------------.------------- ~l~hifium claoatum Cushman ... .--.-....---------------------------- jrigidum Cnshman ...--.------------------------------------------ bartletti Cushman .-------.-..------------------------------------- Pateoria hauerinoides Loeblich and Tappan -..-.--.------------------- Polymorphina sp .....-.-.----------------------- .- -. 

Fissurina sp -.--.--.-......-.----------------------------------------- Buliminella curta Cushman ...--------.-----------------------------.- Ostracodes ---..---..-..,......-------------------------------------- 

EARTHQUAKE EFFECTS 

Species 

- 

Protelphidtumcf.orbiculare(Brady) ....-.-.-.- orbfculare (Brady) ..-...-....------------- Elphidlum clauatum Cushman-- .--.----.. .... subarcticum Cushman -----------.-------- bartletti Cushman ---.-----.-.------------ incertum (Williamson) --.----------------- 

Elphidiella groenlandica (Cushman) ---.-...-.- Quinqueloculina cf. seminula (LinnB) - --.---.- Pateoris hauerinoides Loeblich and Tappan.-. Polymorphina sp- - -.-.--------......--------- Fbsurinasp .-....---.---.--------------------.-.-..-..---...... Dentalina sp ....----.-.-...------------------- Cassidulina lslandica Nfirvang -----.---------- Buliminella curta Cushman --..-....-.-------- Boliufna psaudopunctata H6glund.-. .. . --. -.-- Buccella rigid~ (Cushman) .-----..-.--------- lnw f tat~ Anderson ---...--.--------------- Rosalina sp -...-...-.-.--.-------------------- Dlobigerina bi~lloides d'orbigny - .-.-.-.-.-..-- pcchyd~rma (Ehrenberg) --.-.------------- Ostracodes .....---.---------------------- Mollusk fragments -..-.-...------------------- 

DIRECT SEISMIC EFFECTS tural damage due directly to seis- The cumulative damage was imMost of the more spectacular mic vibration mas subordinate in pressive, and had there been no 

structural damage in the Anchor- terms of total property damage landslides at Anchorage, vibratory 

age area resulted from secondary and financial loss and, for the most effects of the earthquake undoubtcauses such as landslides and part, was relatively unspectacular. edly would have received more 

ground cracks, themselves trig- Nevertheless, the extent of such ef- attention by investigators and by 

gered by seismic vibration. Struc- fects must not be underestimated. the press. 

- 

F 

-.-- 

--.- 

.--. 

-..- 

---- 

R 

---- 

---- 

Sample interval (feet) and boring letter 

- 

F 

---- 

.--- 

---- 

---- 

---. 

.--- 

---. 

.--. 

- - F9 

- 

R 

....-. 

-----. 

.-..-+ 

-.---. 

-.---. 

-.-,-I 

.----. 

.-.--- 

.-.--. 

.----- 

-----. 

----.. 

---.-- 

-.---. 

----.. 

--.-.. 

--.-.. 

.-.--. 

R 

.---.. 

- 

.-.. 

.-.- 

--.. 

--.- 

--.- 

--.- 

.-.. 

--.- 

--.. 

8 

- 

-...-- 

....-. 

-----. 

-.---- 

.----. 

---..- 

-.-.-. 

--.-.- 

.-.--- 

.----- 

.----. 

----.- 

-.---- 

--.--. 

--..-- 

-.-..- 

....-- 

.---.. 

R 

.--.-. 

- 

F 

..-. 

R 

.--. 

-.-. 

---- 

-.-. 

-.-- 

---. 

- - 

7 

- 

es 

-- -..... 

F 

.-.-.. 

.---.- 

..--.. 

-----. 

---... 

-.--.- 

...-.. 

.----. 

R 

.....- 

-. -... 

-.-... 

-.--.. 

----.. 

.-.--. 

.-.--. 

R 

-..... 

- 

R 

.-.- 

--.- 

.-.. 

.-.. 

-.-- 

..-. 

-.-- 

..-. 

ai+ifi# - 

R 

-...-- 

F 

-----. 

....-- 

.---.- 

.-.--. 

..--.- 

-----. 

------ 

R 

.--..- 

------ 

------ 

-.-.-- 

R 

.----- 

--..-- 

R 

.-.--- 

.-.-.. 

------ 

- 

F 

F 

.--- 

..-- 

-..- 

---- 

-..- 

---- 

.-.- 

B 

- 

F 

--.-.. 

-- 

.-.-.. 

-----. 

.----. 

-.---. 

-----. 

.-.-.. 

.----. 

-.-.-. 

-.-..- 

.....- 

-.-..- 

.-.-.. 

.--.-. 

.--.-. 

-----. 

.---.. 

R 

-..-.. 

A 

m 

- 

R 

-.-.-- 

R 

--.-.- 

....-. 

.---.. 

.----. 

R 

-....- 

-.-.-- ----..-....- .-.-.- 

--.-.- 

-.--.- 

--.--. 

--.--- 

-.---- 

------ 

...--. 

-.---. 

R 

-.---- 

- 

R 

---- 

---- 

---- 

--.- 

---- 

.--. 

---- 

---. 

A 

- 

C 

-....- 

------ 

.-.... 

.----- 

.-.--- 

R 

..-.-. 

------ 

.-.--. 

.-.-.. 

.-.-.- 

-.--.. 

-.---. 

----.- 

R 

----.- 

.----. 

...--- 

F 

------ 

- m 

- 

AA 

--.-.. 

-.--.. 

.-..-. 

.-..-. 

.-..-. 

- ...-. 

.-..-. 

-..-.- 

-..-.. 

R 

.----. 

--..-. 

.....- 

-.. --- ----.. 

.---.. 

-..--. 

.-..-. 

.-.--. 

C 

-.---. 

- 

R 

-.-. 

---- 

--.- 

.-.- 

-.-- 

.-.. 

---. 

R 

A 

- 

C 

..-.-. 

-.---. 

.-.-.. 

.----. 

.-.... 

...--. 

-----. 

-----. 

.-.--. --.-.---...--.--.- .-.-.- 

-..... 

.---.. 

----.- 

--...- 

---.-- 

.----. 

-.-.- 

R 

....-. 

---.-. 

- 

A 

.--. 

---- 

--.- 

.-.. 

R 

.--- 

..-. 

R 

- 

AA 

--.--- 

--.-.- 

------ 

-.--.. 

--..-. 

F 

---.-- 

.. 

. 

R 

.....- 

...-.. 

R 

R 

R 

--.-.. 

---... 

R 

F 

-- 

.....- 

-m--e-~~-~$?J4"~4~

4 

- 

AA 

-.---. 

-..-.- 

C 

--.-.- 

------ 

C 

..---- 

C 

F 

-..--. 

R 

R 

-..--- 

---.-- 

-.-..- 

..--.- 

...-.- 

-- 

F 

------ 

- 

.--. 

---- 

-.-. 

---- 

.--- 

---. 

.--- 

--.- 

.-.- 

$jtjij$ - 

B 

-----. 

------ 

----.. 

-----. 

--.--. 

.. . 

.----. 

-- 

.. 

R 

.-.... 

-..-.- 

--...- 

.-.--. 

....-. 

--.-.- 

-....- 

.-.... 

. 

-- 

.---.. 

gjc.&gg~5sgGj;;~ - 

A 

-----. 

-.---- 

-----. 

F 

...-.- 

F 

C 

-- 

C 

R 

..--.. 

.---.. 

------ 

. -. -. ..-..- 

.-.-.. 

--.-.- 

.-.... 

-- 

C 

R 

-- 

F 

-..- 

..-- 

.... 

..-. 

-.-- 

-.-. 

-..- 

...- 

h-hhh--h 

- 

A 

F 

-.---- 

--..._ 

. 

.-.... 

C 

C 

C 

C 

F 

R 

...-.- 

.----- 

. -. -. 

-.---- 

..--.- 

...-.- 

.-.--- 

. 

C 

-.--.- 

sx3s I 

- 

10 

A 

_.._.. 

------ 

...--- 

C 

R 

-.-.-. 

.-.-.- 

C 

F 

A 

F 

.--.-- 

------ 

R 

-..-.- 

C 

R 

....-. 

R 

C 

.-.-.- 

- 

F 

--.- 

---. 

---- 

.--- 

---- 

-.-. 

-.-. 

F 

A 

-..-.- 

.----- 

------ 

C 

------ 

-----. 

.---.- 

F 

R 

F 

R 

.-.-.- 

------ 

- --- - - ---.-- 

R 

--.-.- 

.-.-.- 

------ 

C 

----.. 

j: 

- 

A 

C 

--.--- 

--..-. 

F 

.-.--. 

.-..-. 

C 

C 

.. 

F 

F 

.-.--. 

--.-.- 

. . . -. ...-.. 

...-.. 

---..- 

.-.-.. 

.. 

C 

-.-.-. 

- 

A 

----.- 

..---- 

----.. 

C 

.--.-- 

-.---. 

----.- 

C 

R 

C 

...-.. 

-....- 

- - -- .- 

...-.. 

--.--- 

--.-.. 

-.-..- 

R 

C 

..--.. 

4 

rf 

-- 

A 

--.-.- 

----.- 

------ 

C 

-.-.-. 

-.---- 

.-.-.. 

C 

F 

F 

R 

.----. 

------ 

------ 

-----. 

------ 

.-.-.. 

.-.-.. 

...-.- 

C 

--.-.. 

- 

R 

R 

...- 

..-. 

.--. 

---. 

.--- 

.-.- 

.-.- 

- 

C 

.--- 

---- 

F 

F 

---. 

R 

.-.- 

--.- 

- 

A 

F 

-.-. 

---- 

F 

F 

R 

---- 

A 

- 

A 

..-- 

..-- 

F 

R 

---- 

-.-- 

. .-. 

R 

- 

F 

.... 

---. 

---. 

--.- 

.--- 

.--- 

..-. 

..-- 

- 

F 

.-.- 

-.-- 

-... 

--.. 

R 

.-.- 

.-.- 

---. 

F 

-... 

---- 

---- 

---- 

-.-- 

.--- 

R 

-... 

- 

-.-- 

---- 

..-- 

--.- 

---. 

---- 

---- 

---- 

---. 

- 

C 

---- 

---- 

.--- 

.--. 

..-- 

.-.- 

.-.- 

.--- 

-- 

F 

-- -- .--- 

-... 

--.- 

.-.- 

---- 

---. 

---- 
ALASKA EARTHQUAKE, MARCH 2 7, 1964 

Vibratory damage to buildings 

and other structures is not strictly 

a geologic effect, but the extent 

and amplitude of vibration is dependent partly on geologic factors 

such as foundation and subfoundation conditions. Other things being equal, vibration is more intenw 

and damage is greater in areas of 

thick unconsolidated deposits thsan 

in areas of bedrock. Examples of 

this rule are too numerous and too 

widely recognized to need documentation. All the severe vibratory damage in the Anchorage 

Lowland was in areas underlain 

at some depth by Bootlegger Cove 

Clay. Design and construction 

practices, on the other h'and, are 

critical nongwlogic factors that influence building performance and 

vibratory damage. As pointed out 

by Berg and Stratta (1964, p. 58), 

structural weaknesses are quickly 

ferreted out by earthquakes. 

Inasmuch as this report emphasizes primarily the geologic effects 

of the March 27 earthquake in the 

Anchorage area, only the highlights of the vibratory effects are 

summarized here. Detailed analyses of structural response to vibratory st- have been presented 

by several authors (Berg and 

Stratta, 1964; McMinn, 1964; National Board of Fire Underwriters 

and Pacific Fire Rating Bureau, 

1964; Steinbrugge, 1964), and the 

following summary is baaed 

largely on their findings. 

The distribution and character 

of direct seismic damage were unusual to say the least. Prdbably 

few buildings in the Anchorage 

area were totally undamaged, but 

many blocks of honles and small 

commercial buildings received cursory damage at most and sustained 

virtually no damage to structural 

members, frameworks, or foundations. Many chimneys toppled, 

and quite a few fireplaces separated from adjoining exterior 

walls. Indoors, plaster cracked 

and objects were thrown to the 

floors of many homes. On many 

buildings however, fragile decorative facings, pillars, and cornices 

were unscathed. Church steeples 

remained standing. Headstones 

in cemeteries--long used as indicators of earthquake intensitystood untoppled throughout the 

area. Large elevated well-guyed 

water tanks were undamaged (fig. 

6), although trees whiplashing 

back and forth touched the ground 

on either side according to eyewitnesses. On the other hand, multistory buildings and buildings 

having large floor areas commonly 

sustained significant structural 

damage ; several such buildings 

were total losses (figs. 5 and 13), 

and many required major repairs. 

Thus, direct seismic damage was 

highly selective. Aside from variations in design, construction 

practice, and workmanship, ltarge 

buildings were more severely damaged than small ones. Inertia, was 

a fac'tor, of mum; other khings 

being equal, heavy structures are 

more suscept$ble to vilbratory damage than light ones. 

Steinbrugge (1964, p. 58-72) 

has described vibratory damage effects in the Anchorage area in 

terms of engineering seismology. 

He ascribed (p. 59) the selectivity 

of the effects to the great magnitude of the quake and the distance 

of Anchorage from the epicenter: 

"The ground motion at Anchorage 

did not appear to contain significant short period motion which has 

been commonly observed in epicentral regions of destructive 

shocks." He added (p. 71) : "The 

earthquake damage in Anchorage 

was selective * * *. This damage pattern appears to be attributable to the distance that Anchorage was from the epicenter, 

with the longer period ground motion having n dominant effect at 

this distance." According to 

White (1965, p. 91), attenuation 

of sinusoidal seismic waves at low 

frequencies should vary as the 

square of the frequency. Where 

seismic vibrations have long periods and large amplitudes, distortion and strain are far more severe 

in large structures than in small 

ones. The reason for the selectivity of the March 27 earthquake at 

Anchorage is thus apparent. The 

prolonged duration of the shaking 

must also have heightened all other 

effects; as mentioned before, strong 

motion lasted 3 to 4 minutes, possibly longer. 

In general, most buildings outside of landslide areas withstood 

well the effects of the earthquake. 

The low loss of life is, in some 

measure, a tribute to the structural 

soundness of most of the larger 

buildings but in part also is the 

result of the low susceptibility of 

smaller structures to the long- 

~eriod vibrations that racked the 

area. All the high-rise structures 

in Anchorage (10 stories or more) 

sustained moderate to heavy damage without collapse or loss of life. 

Four structures of medium 

heightfour to nine stories-collapsed or were damaged beyond 

repair. Several low buildings of 

less than four stories were totally 

destroyed, but most such structures 

were damaged little or not at all. 

In the general downtown area, 

outside the Fourth Avenue and L 

Street slides, 'a 5-story department 

store (J. C. Penney Co.) was a total loss, 4 buildings 1 or 2 stories 

high were heavily damaged, 9 

buildings 1 to 14 stories high SUStained moderate damage, and 

about 22 buildings received light 

damage (National Board of Fire 
EFFECTS AT ANCHORAGE 

Underwriters and Pacific Fire 

Rating Bureau, 1964, p. 26). In 

the same area, however, many single family dwellings, stores, and 

small commercial buildings were 

damaged little if at all. Steinbrugge (1964, p. 71) found no evidence to indicate that one construction material \\-as superior to another, given comparable attention 

to design and construction. 

A few buildings seem to have 

been designed without regard to 

earthquake stresses. The Hillside 

Apartments and various warehouses that collapsed were examples. In other buildings, 

inadequate conneotions between 

structural parts were the most 

common causes of failure ; improperly welded joints, inadequate tiss 

in reinforced-concrete members, 

and improperly spliced reinforcing rods all were loci of failure. 

Welded precast- and prestressedconcrete structural m e m b e r s 

seemed to be particularly susceptible to joint failure, although some 

buildings so framed were undamaged. In some buildings, construction joints were inadequately 

keyed. Poured nonmonolithic 

concrete joints were sites of shear 

failures, and some concrete appeared to be substandard. Most 

poured-in-place concrete structures, however, fared well. In 

some multistory buildings, provisions for vertical shear were inadequate to withstand a stress of 

the intensity generated by the 

March 27 earthquake (Berg and 

Stratta, 1964, p. 58). 

Small wood-frame buildings 

outside areas of ground displacement were generally little damaged (Steinbrugge, 1964, p. 63- 

64). Unreinforced masonry walls 

and chimneys were usually intact, 

and most interior wooden stud 

walls sustained nothing more than 

minor nonstructural cracking. 

Foundations of poured concrete or 

hollow concrete block (some apparently unreinforced) generally 

were intact. Usually windows 

were unbroken, and objects remained on shelves indoors. 

Of the many buildings damaged 

or destroyed by direct seismic vibration in Anchorage, several 

structures described briefly be10117 

are most significant for the damage or lack of damage they sustained, relative to design and 

construction p r a c t i c e. These 

structures, therefore, have received 

the most attention from investigators. The folloving synopsis is 

based mostly on the reports of 

Berg and Stratta, Steinbrugge, 

and the National Board of Fire 

Underwriters and Pacific Fire 

Rating Bureau. 

ALASKA PSYCHIATRIC INSTITUTE 

The three-story steel-framed 

A 1 a s k a Psychiatric Institute, 

southeast of the main part of Anchorage, is notable because it sustained so little damage. There 

were minor cracks in stair wells 

and broken pipe hangers and machinery mounts in the penthouse. 

The nearby new Providence Hospital and the Alaska Methodist 

University also were little damaged. Significantly, perhaps, 

these three buildings are outside 

the area underlain by Bootlegger 

Cove Clay. 

THE ALASKA RAILROAD 

MARSHALLING YARDS 

Several buildings in the Alaska 

Railroad marshalling yards were 

damaged. Warehouses collapsed 

and shops were slightly damaged. 

The steel-framed wheel-s h o p 

building partly collapsed and has 

since been torn down. Some buildings were in or near the toe area 

of the Fourth Avenue landslide 

and, hence, may have been subjected to ground displacements as 

well as to seismic vibration. 

ALASKA SALES AND SERVICE 

BUILDING 

The one-story Alaska Sales and 

Service Building on East Fifth 

Avenue at Medfra Street was under construction but was structurally almost complete at the time 

of the earthquake; it was a total 

loss. Collapse is attributed chiefly 

to failure of melded connections 

between T-shaped precast-concrete 

columns and roof beams, caused 

either by the breaking of welds or 

tearing out of bar inserts. The exterior precast-concrete walls of the 

building partly collapsed when the 

roof gave way. 

ANCHORAGE INTERNATIONAL 

AIRPORT 

The Anchorage International 

Airport control tower, a reinforced-concrete structure, collapsed to the ground (fig. 7), killing one occupant and injuring another and damaging the connecting walls of the adjacent terminal 

building. The terminal building 

was otherwise little damaged. At 

the airport post office building, a 

rear mall pulled away from the 

roof trusses and leaned outward; 

moderate nonstructural damage 

was sustained indoors. 

ANCHORAGE WESTWARD HOTEL 

The steel-framed Anchorage 

Westward Hotel complex is just 

west of the Fourth Avenue landslide area facing Third Avenue between E and F Streets and is within the area of peripheral cracking. 

Several cracks passed through the 

building foundations and first 

floors. Some cracks had vertical 

offsets. There was little visible 

damage to the flexible exterior 

metal skin of the 14-story tower, 

but there was significant structural 

damage (since repaired) to the 

more rigid interior structural elements. Reinforced-concrete columns were buckled, and rein- 
A24 ALASKA EARTHQUAKE, MARCH 2 7, 19 64 

forced-concrete shear walls were 

damaged. An interior east-west 

shear wall had failures above all 

door openings in every story. At 

the eight-story level there was 

shear-wall damage along a horizontal join between older and 

newer sections of the building. 

Considerable damage was caused 

by pounding between the 14-story 

tower and the adjacent 3- and 6- 

story wings. 

CORDOVA BUILDING 

The Cordova Building is a sixstory structure at the northeast 

corner of Sixth Avenue and Cordova Stmt. The damage ms 

mostly light and was caused chiefly 

by an east-west movement of the 

building. This direction is parallel to the shorter dimension of the 

floor plan and also is the direction 

of great& strength in the steel 

support columns (Berg and 

Strakta, 1964, p. 37). Damage was 

mainly in the first story. The 

southeast-corner support column 

failed below the second-floor beam, 

and the exterior reinforced-concrete curtain walls sheared at the 

top of the basement; the corner 

broke away at the first and second 

stories. The center column in the 

south wall buckled. The reinforced-concrete stair and elevator 

shaft sheared at the b~se of the 

first story. The penthouse collapsed. Repairs have since been 

completed. 

ELMENDORF AIR FORCE BASE 

At Elmendorf Air Force Base 

the reinforced-concrete control 

tower was damaged by cracks extending from its base to a height 

of about 15 feet. A warehouse 

('No. 21-884) partly collapsed 

when roof-beam anchor bolts 

pulled away from poured-in-place 

concrete piers. The Elmendorf 

Field House vas slightly damaged at the roof corners and at 

the junctions of the side walls with 

the steel frame. Elmendorf Hospital was damaged by X-shaped 

shear fraotures in block-panel 

walls at the second- through the 

fifth-story levels, by interior failures nt a few reinf orced-concrete 

columns and at the elevator shaft, 

and by some movement between 

different sections of the building. 

Damage has since been repaired, 

repoMly ak a cost of more than 

$1 million (R. M. Waller, written 

commun., 1965). 

FIFTH AVENUE CHRYSLER 

CENTER 

The one-story Fifth Avenue 

Chrysler Center just north of 

Merrill Field was a total loss. It 

had a precast- and prestressed-concrete T-beam roof supported by 

concrete-block walls. .The front 

of the building collapsed and the 

T-beam roof fell in on the showroom. The hollow-core concreteblock side walls failed at the rear 

corners of the building. 

FIRST FEDERAL SAVINGS AND 

LOAN BUILDING 

The three-story First Federal 

Savings and Loan Building is located at the northwest corner of 

Fifth Avenue and C Street. 

Ground cracks opened parallel to 

its east and south walls evidently 

in back fill. Even though the east 

and south faces of the building are 

mainly glass, there was little glass 

breakage. The west and north 

walls and the brick panels in the 

east wall sheared horizontally 

through the second story. The 

building has been repaired. 

FOUR SEASONS APARTMENT 

BUILDING 

The Four Seasons Apartment 

Building at West Ninth Avenue 

and M Street was a spectacular 

total loss (fig. 13). It was designed for year-round luxury living, but didn't survive its first season. The building was nearing 

completion at the time of the earthquake, but fortunately it was not 

yet occupied-it collapsed in a pile 

of rubble. It was a six-story liftslab reinforced-concrete building 

with two central poured-in-place 

cores, one for a stairwell and one 

for an elevator. The floor slabs 

were torn loose from shear heads 

on the structural-steel columns and 

pulled away from keyways in 

the stairwell and elevator cores. 

Some dowels connecting the slabs 

to the cores broke; others were 

pulled free. 

The collapse of the Four Seasons Apartment Building was witnessed from 1000 Tenth Avenue by 

Glen L. Faulkner, a consulting 

geologist, who reported (oral commun., 1964) that the building collapsed just before the end of the 

quake, after shaking violently for 

perhaps 2 to 3 minutes. Just before it fell, it seemed to start crumbling near the second-floor level in 

the area of its northeast corner. 

Then with a slight tilt northward 

it collapsed vertically in a great 

cloud of dust. The two central 

cores were left leaning sharply 

northward. The steel support columns fell to the north also, and 

the slab floors were stacked one on 

another like pancakes. 

The effects of seismic vibration 

in areas of cracked ground cannot 

always be separated from the effects of ground displacement. 

The collapse of the Four Seasons 

Apartment Building (fig. 13), a 

case in point, has been attributed 

to seismic vibration. Perhaps vibration was the dominant factor 

in the building's failure. The 

building, however, was close to the 

L Street graben at West Ninth 

Avenue and M Street, and a large 

subsidiary f r a c t u r e, trending 

about west-northwest, passed directly under the building. In the 

chaotic pile of rubble left after the 
EFFECTS AT ANCHORAGE A25 

13.-Wreckage of six-story Four Seasons Apartment Building, Anchorage, Alaska. Canted elevator shaft at center. Large 

crack in foreground, filled in on M Street to restore traffic, passed beneath building. 

quake, the fracture may have been 

overlooked by early investigators. 

Furthermore, part of the fracture 

was quickly bulldozed over to restore traffic along M Street. In 

any event, the fracture was 

mapped by the Engineering Geology Evaluation Group, and its extensions east and west were still 

well preserved 2 months or more 

after the quake. Near the building the fracture had a vertical displacement of about 2 feet; the 

north side dropped down-a displacement that few manmade 

structures could be expected to 

withstand. The actual displacement beneath the building, however, is uncertain. The fact that 

the elevator shaft and stair well of 

the building fell northward suggests that they tilted in that direction in response to the northward 

displacement along the fracture. 

Support pillars collapsed in the 

same direction. 

The building reportedly withs'tood most of the earthquake, although it shook violently, but it 

collapsed suddenly shortly before 

the end of the quake. Eyewitness 

accounts of the L Street slide 

(Shannon and TITilson, Inc., 1964, 

p. 53) indicate that sliding there 

occurred in the latter part of the 

quake. The timing seems more 

than coincidental; the crack beneath the Four Seasons Apartment Building must have attained 

offset at about the same time. It 

could not have had offset until the 

slide itself had begun. 

HILL BUILDING 

The Hill Building, an eightstory office building at the southeast corner of Sixth Avenue and 

G Street, \I-as slightly damaged. 

There apparently was no damage 

to the steel frame, and these \\-as 

little exterior damage. A reinforced-concrete column failed at 

its junction with the canopy roof 

of the service entrance. The center cores, which were intended to 

resist horizontal forces, dropped as 

much as 5 inches at one point and 

3 inches at another where they 

were partly shattered at their connections with the footings. The 

core \rails were cracked also, and 

the beams between the cores were 

sheared by vertical stresses. 

HILLSIDE APARTMENTS 

The Hillside Apartments were 

on the south side of Sixteenth 

Avenue between G and H Streets 

on a bluff overlooking Chester 

Creek. They were damaged beyond repair and have since been 

dismantled. This was a split-level 

building, fire stories high on the 

south side and three stories high 

on the street side. It had a postand-lintel frame with steel-pipe 

columns, rolled-steel beams and 

concrete floor slabs on steel joists. 
A26 ALASKA EARTHQUAKE, MARCH 27, 1964 

Walls were unreinforced hollow 

concrete block. The building was 

sheared in an east-west direction 

a;t the third-story level on the 

south side and in the lower two 

stories on the north side-the upper stories lurched west rellative 

to the lower stories. 'Seemingly, 

no provision had been made for 

resistance to strong lateral seismic 

stress. 

KNIK ARMS APARTMENT 

BUILDING 

The six-story Knik Arms 

Apartment Building, of pouredin-place reinforced-concrete framing, is on the west side of L Street 

between Sixth and Seventh Avenues, on the L Street landslide 

block between the headward gqben and the bluff overlooking 

Knik Arm. It is especially noteworthy for its apparent lack of 

damage, despite a lateral displacement of about 10 feet west-northwest as it was carried along with 

the underlying slide block. Many 

smaller residential buildings on 

the slide block were also undamaged or little damaged. 

MOUNT McKINLEY BUILDING AND 

1200 L STREET APARTMENT 

BUILDING 

The Mount McKinley Building 

and the 1200 L Street Apartment 

Building are twin 14-story reinforced-concrete apartment buildings about a mile apart and facing 

in opposite directions. They sustained similar damage, almost 

matching crack for crack, although damage in general was 

somewhat more severe in the 

Mount McKinley Building. The 

Mount McKinley Building is on 

Denali Street between Third and 

Fourth Avenues; the 1200 L 

Street Apartment Building is 

across town near Inlet View 

School. 

The most obvious damage to 

both buildings was X-shaped shear 

cracks in spandrel beams, caused 

by vertical shear between exterior 

support piers as 'a result of lateral 

swaying. Spandrels in general 

were most heavily damaged in the 

middle third of the floor levds. 

Interior walls were less damaged 

than exterior ones. 

In the Mount McKinley Building, vertical piers sheared horizontally at the third-story level 

on the north side of the building 

(at a construction joint) and at 

the second story on the south side. 

An exterior column fractured diagona<lly at the first-story level. A 

*television-antenna tower on top of 

the building was undamaged. 

Failures similar to those in the 

Mount McKinley Building occurred in the 1200 L Street Apartment Building in piers at the 

south face of the building at the 

second- and third-story levels. 

Corner spandrels were more heavily damaged than those in the 

Mount McKinley Building. 

An account of the earthquake 

as related by an occupant of the 

12th story of the 1200 L Street 

Apartment Building was provided 

by William G. Binkley (written 

commun., 1964). Mr. Binkley, a 

geologist, noted wryly that he was 

living in a sort of oversized seismograph. The quake was first felt 

in the building as a light tremor 

that intensified rapidly until objects began to fall to the floor. 

About 30 seconds of trembling motion was followed by perhaps 2 

minutes of violent jarring, in 

which the building seemed to sway 

8 to 10 feet horizontally and 1 to 2 

feet vertically. Bookcases were 

overturned, and fallen books and 

furniture were thrown back and 

forth across the room. Violent 

shaking was accompanied by a 

deep rumble and by higher pitched 

sounds of shattering plaster and 

falling dishes and furniture. In 

the kitchen, everything from the 

cabinets and refrigerator crashed 

to the floor, where it was "churned 

into a melange of broken dishes 

and glass, catsup and syrup, flour, 

beans, pots and pans, eggs, lettuce, 

and pickles." Mr. Binkley was 

able to crawl from the living room 

to a hall where he braced his feet 

against one wall and his back 

against another. Then the building stopped "jumping," the noise 

stopped abruptly, and the motion 

of the building diminished gradually with a subsiding, weaving 

tremble. 

Most people at ground level experienced far less violent shaking 

than those in tall buildings. Many 

individuals were unaware of the 

catastrophic proportions of the 

quake until much later when the 

reports began to come in. In the 

heights of the 1200 L Street Apartments, however, the accelerations 

undoubtedly were greatly magnified. 

PENNEY'S DEPARTMENT STORE 

BUILDING 

The Penney's Department Store 

Building (fig. 5) was a total loss 

and has since been dismantled. 

Photographs of its wreckage have 

been widely distributed in magazines and newspapers. Penney's 

was a five-story reinforced-concrete structure having shear walls 

on three sides and a curtain wall 

of precast panels on the north. 

Failure is attributed to torsion 

caused by rotational displacements, in turn caused by an eccentric position of the center of 

rigidity of the structure. This 

rotational motion sheared off the 

west support wall at the secondstory level, causing the wall and 

all overlying floors to collapse. 

The floor slabs also sheared at 
EFFECTS AT ANCHORAGE 

their connections to the next adjacent column wall to the east. The 

northeast corner of the building 

collapsed (fig. 4), and most of the 

precast panels on the north face 

fell to the street. Berg and Stratta 

(1964, p. 35) reconstructed the sequence of events as follows: The 

northeast corner of the building 

collapsed following failure of the 

east shear wall at that point; the 

west shear wall then failed at the 

second-story level at the north end 

of the building. The east shear 

wall failed at the south end of 

the building, and the precast 

curtain-wall panels collapsed at 

the north face of the building. 

The north-facing curtain wall 

must have fallen rather late in the 

quake. Some motorists reportedly 

were able to start their ptxrked cars 

and move them away from below 

the wall before it fell. One motorist who ran to her car in an attempt to move it, however, was 

trapped and killed (R. M. Waller, 

written commun., 1965). 

PORT OF ANCHORAGE AREA 

Much of the damage in the Port 

of Anchorage area was caused by 

ground displacements along fractures, but some damage is attrib- - 

utable to direct seismic shaking. 

The main pier lurched laterally 5 

to 19 inches. Large longitudinal 

cracks and several transverse ones 

opened up, and the walls of several 

buildings were cracked. All four 

gantry cranes were damaged. 

Steel piles penetrated the deck of a 

subordinate pier. Approach roads 

and railroads settled as much as 18 

inches. Two cement-storage tanks 

were toppled, one at the property 

of the Permanente Cement Co. at 

the entrance to the U.S. Army 

Dock and one at the Alaska Aggregate Corp. facility just north 

of Ship Creek. Oil-storage tanks 

in the dock area were mostly superficially damaged, but some tanks 

were bulged outward at the bottom, probably by rocking and 

pounding back and forth as the 

contents sloshed to and fro. 

WEST ANCHORAGE HIGH SCHOOL 

West Anchorage High School is 

on the south side of Hillcrest Drive 

a few blocks west of Spenard Road 

and just south of a bluff overlooking Chester Creek. Structurally 

separate parts of the school building reacted differently to the vibrations. The two-story classroom 

section of the building was heavily 

damaged, especially the second 

story. Exterior columns failed at 

connections with the roof and with 

the second-floor spandrels. Extensive damage was caused by 

pounding between the gymnasium 

section and the classroom section. 

There was extensive ground cracking along the bluff above Chester 

Creek and a small rotational 

slump formed due north of the 

school. 

GROUND DISPLACEMENTS 

OTHER THAN LANDSLIDES 

GROUND CRACKS AND 

COMPACTION 

The distribution of ground 

cracks in the Anchorage area (generalized in fig. 1) was mapped by 

the Engineering Geology Evaluation Group (1964, pl. 1) shortly 

after the earthquake. Most of the 

observations on which this map is 

based were made on traverses adjacent to streets and highways but 

some were obtained from a scrutiny of aerial photographs. Many 

unobserved cracks probably formed in the less-accessible snow-covered undeveloped areas. Frozen 

muskeg in and bordering swamps, 

for example, was very susceptible 

to cracking. The map, nevertheless, shows clearly the widmpread 

distribution of cracking, and it emphasizes the high susceptibility to 

cracking of lowland areas underlain by silty clay and outwash, as 

opposed to highland areas underlain by ground moraine. Made 

land in former muskeg areas, reclaimed either by draining or by 

filling directly over muskeg, was 

also very susceptible to cracking. 

Reportedly, many ground cracks 

opened and closed with the rhythm 

of the earthquake. Such action 

may help explain the extensive 

damage some cracks caused. A 

pulsating fracture would cause 

more damage to a superencumbent 

structure than a fracture that 

merely opened. 

The most severely cracked 

ground was adjacent to landslides 

(fig. 40) where cracks were caused 

by tension directly related to sliding. The cracks in turn caused 

much structural damage in builtup areas. Some cracked ground 

undoubtedly would have developed into landslides had the earthquake lasted longer, as for example at Turnagain Heights, back of 

the landslide (pl. 1). Here, the 

pattern of fracturing was concentric to the head of the slide, and 

many crescentic tension cracks extended as far as 2,200 feet from the 

slide proper, to the vicinity of 

Northern Lights Boulevard. In 

the downtown area, many stmts 

and buildings mere damaged by 

cracks behind the periphery of the 

Fourth Avenue slide. Major 

cracking and ground adjustments 

extended a city block or more back 

from the slide. In contrast, the L 

Street and Government Hill slides 

broke away clean ; they were much 

cracked themselves, but few cracks 

extended behind them. 

Preexisting zones of weakness in 

the ground were particularly 

susceptible to cracking. Some 

cracks followed backfilled utility 

trenches, for example, or backfills 
A28 ALASKA EARTHQUAKE, MARCH 2 7, 19 6 4 

around building foundations. Old 

frost cracks in pavementcaused 

by contraction at low temperatures-were reopened by the earthquake; at Turnagain Heights, the 

pattern of cracking was very striking-ground cracks veered along 

concrete curbings, crossed streets 

at right angles along old contraction cracks, and then resumed dimotion on the other side. In filled 

areas, cracks wmmonly formed 

near the contact 'between filled and 

preexisting ground. Some buildings unfortunately constructed 

partly on fill were sundered by 

cracking between the fill and the 

adjacent ground. 

Trees were split by cracks that 

passed through their root systems 

(fig. 40), their roots being held 

fast by the frozen ground. 

On sloping ground, cracks generally formed parallel to the slope, 

owing to differential compaction, 

lateral shifting (lurching) under 

the influence of gravity, tension, 

and rupture. 

Alternate cuts and fills along 

streets, highways, and railroads 

demonstrated a predictable pattern of fractures. Fills that compacted under the vibratory stress 

of the quake were cracked adjacent 

to the fill-cut contact. Many 

cracks of this sort crossed the 

Seward-Anchorage H i g h w a y, 

some fills dropping several inches. 

One in particular formed a very 

sharp pavement break on the north 

approach to the Rabbit Creek 

crossing near the south margin of 

the Anchorage Lowland. Similarly, an Alaska Railroad embankment across Fish Creek east of 

Turnagain Heights cracked to 

pieces and collapsed. 

Extensive ground cracks formed 

in the Port of Anchorage area on 

the flats extending north from the 

mouth of Ship Creek to and be- 14.-Ground cracks, Port of Anchorage and vicinity. Anchorage, 

yond City Dock between the bluff Alaska. Many of these cracks spouted mud, particularly those east 

on the east and the shore of Knik of City Dock. Base by city of Anchorage, Office of City Engineer. 
EFFECTS AT ANCHORAGE A29 

Arm on the we& (fig. 14). This 

area is underlain by estuarine silk, 

peat, muskeg, and artificial fill 

(Engineering Geology Evaluation 

Group, 1964, p. 22), all highly 

susceptible to cracking under the 

stresses of prolonged vibration 

and compaction. ~ieat quantities 

of mud were extruded from large 

polygonal fractures in the flats 

northeast of City Dock. To the 

south, longitudinal cracks 300 feet 

or more long extended the full 

length of the Army Dock embankment. At the south end of the 

embankment, in an area of transverse cracks, a steel cement-storage 

tank was overturned. Collapse of - 

the tank, however, may have been 

caused by inadequate anchoring of 

base plates to support columns 

('Berg and Stratta, 1964, p. 46). 

Facilities south of the Army 

Dock to the west of Ocean Dock 

Road were also damaged by 

ground cracks. #Cracks extended 

through the tank farm of the 

Union Oil Co. of California and 

damaged the adjacent Alaska Fish 

and Farm Products lease and the 

Cook Inlet Tug and Barge lease. 

There was ground cracking in the 

dock area at the mouth of Ship 

Creek, where another cement storage tank toppled and where the 

right abutment of the adjacent 

Alaska Railroad bridge across 

Ship Creek was damaged by subsidence and cracking. 

Incipient and minor slumping 

along the bluff east of the dock 

area also produced many cracks, 

some of them large. All these, 

however, were in undeveloped 

woodland areas, mostly on military land. 

SAND BOILS AND MUD 

FOUNTAINS 

Sand boils and mud fountains 

are transient or short-lived features commonly produced by 

15.-Part of a sand boil, Turnagain Heights slide area. Ridges 2 to 3 feet high and 

100 feet long or more were formed as fountains of water were ejected through 

frozen outwash. 

strong earthquakes where ground 

breakage occurs. They were wide 

spread in the damage zone of the 

March 27 Alaskan earthquake 

(Grantz, Plafker, and Kachadoorian, 1964, p. 6). At Anchorage they have been reported at 

several localities and probably occurred in many others. 

Mud fountains were produced 

where the water table was shallow 

and frozen ground overlying saturated, unconsolidated sand or silt 

was cracked by the earthquake. 

Intense shaking possibly accompanied by settlement and compaction forced muddy water out 

through the cracks. 

At the Port of Anchorage, mud 

was ejected from many cracks east 

and northeast of the City Dock 

and from a few cracks between the 

Army Dock and Ship Creek. The 

ground was snow covered at the 

time, and consequently the ejected 

mud shows plainly on aerial photographs taken shortly after the 

earthquake. 

A mile above the mouth of 

Chester Creek, where Spenard 

Road crosses it, large mud fountains were reported by a motorist 

whose passage was blocked by 

cracks in the road. The fountains 

reached higher than his car (R. 

D. Miller, oral commun., 1964). 

At Turnagain Heights, large 

sand boils, unlike any others in the 

area, resulted from agitation and 

settlement of slump blocks within 

the landslide (fig. 15). These boils 

built ridges of sand 2 to 3 feet 

high, 3 to 6 feet wide, and about 

100 feet long. Some ridges had 

hollo\~- cores. The stand generally 

was finer grained than the subjacent outwash, from which it must 

have come, and it may, therefore, 

have been sorted by natural elutriation in a pulsating water column. 

A large kidney-shaped boil near 

Turnagain Heights, but outside 

the landslide area, spread over an 

area of about 3,200 square feet. 

This boil was just west of a collapsed Alaska Railroad embankment across Fish Creek one-fourth 

mile north of Northern Lights 

Boulevard (Engineering Geology 
ALASKA EARTEQUAKE, MARCH 27, 1964 

16.-Diagrammatic section near Point Campbell, showing mode of failure along bluff line overlooking Turnagain Arm. 

Evaluation Group, 1964, pl. 8). 

TWO other large boils poured out 

of the opposite side of the same 

embankment. They may have 

been caused by spontaneous liquefaction of subjacent silty sand, 

that was pumped to the surface 

when the embankment fill collapsed. Several similar but 

smaller boils formed in the downtown area in the toe of the Fourth 

Avenue slide, east and just below 

the intersection of E Street and 

West Second Avenue (Engineering Geology Evaluation Group, 

1964, pl. 5). 

Most of the lakes in the Anchorage area-solidly frozen over at 

the time of the quake-developed 

distinctive patterns of peripheral 

ice cracks extending generally 50 

to 100 feet out from shore but in 

places much farther. The fracture zones in the larger lakes were 

wider than those in the smaller 

ones, and some small lakes had no 

cracks at all. Most of the cracks 

ejected fountains of water during 

the quake, and where the bottom 

was shallow enough they ejected 

mud, particularly in toll-ard shore. 

Large mud fountains formed at 

Lake Otis (on the northeast 

shore), Lake Spenard, Hood Lake, 

and Connors Lake, to name a few. 

The earth dam impounding 

Campbell Lake, near Turnagain 

Arm, broke during the earthquake. 

As the water level fell, ice on the 

lake broke into blocks, and fountains of muddy water squirted up 

through the cracks. Reportedly, 

these fountains reached heights of 

20 feet or more. 

LANDSLIDES 

DEBRIS SLIDES, AVALANCHES, 

AND ROTATIONAL SLIDES 

Landslides precipitabd along 

the bluffs of Knik and Turnagain 

Arms and along the benches above 

Ship Creek were the most spectacular and awesome manifestations 

of earthquake damage in the area. 

The slides took several forms and 

occurred in several types of earth 

material. The most destructive 

slides, in terms of property damage, resulted from failures in the 

Bootlegger Cove Clay. Serious 

failures, however, also occurred in 

glacial till, delta deposits, 'and 

dune sands-the only criteria being unconsolidated surficial deposits having insufficient shear 

strength to resist the accelerations 

of the quake in potentially unstable topographic settings. A 

landslide occurs where the ratio 

of shearing resistiance of the 

ground to the shearing stress on 

the potential slide surface decreases from a value greater than 

one to unity. An earthquake can 

cause an almost instantaneous decrease in this ratio (Terzaghi, 

1950, p. 110). 

SLIDES ALONG TURNAGAIN ARM 

Structurally, the simplest slides 

were in the bluffs facing Turnagain Arm southeast of Point 

Campbell (fig. 16). There, a thin 

cover of wind-blown sand and 

slope wash had been loosely anchored to thssteep face of the bluff 

by an overgrowth of trees, shrubs, 

and grasses. The entire superficial 

mat, probably frozen at the time, 

slumped downward a few inches to 

several feet along the full length 

of the bluff from Point Campbell 

to Campbell Creek, a distance of 

about 4 miles. Locally the slumping was more intense, and the face 

of the bluff was laid bare from top 

to bottom. Southeast of Campbell 

Creek, minor or incipient slumping 

and cracking extended along the 

bluff to the tracks of The Alaska 

Railroad near Potter, where slides 

destroyed trackage and embankments. 

Between Point Campbell and 

Campbell Creek, the earth slid 

either in a mass, as a shallow nonrotational glide, or it disintegrated 

into blocks and fragments, as a 

debris slide or avalanche (Varnes, 

1958, pl. 1). All intermediate steps 

are represented. The velocity of 

motion has not been ascertained, 

but it probably was rapid because 

of the height and steepness of the 

slope and the granular incoherent 

character of the material. 
EFFECTS AT ANCHORAGE 

Trees carried along in the slides 

were tilted at all angles of disarray, many were rotated outward, 

some inward, and some were overridden by surging at the base of 

the slope. In some places the debris surged out into lobate forms 

on the estuarine muds and swamps 

at the foot of the bluff, and in 

many places one, two, or three 

pressure ridges were formed at the 

foot of the slope or out on the flats. - 

Some ridges were more than a 

thousand feet from the bluff. The 

flats below the bluff were snow 

covered at the time and probably 

frozen. Pressure probably was 

transmitted directly from the slide 

through the frozen layer to the 

points of failure on the flats. 

The high, steep part of the bluff 

nearest Point Campbell consists 

chiefly of loose deltaic sand and 

gravel veneered with dune sand. 

The bluff supported little or no 

vegetation prior to the earthquake 

because of more or less continuous 

buffeting by storm waves. It had, 

theref ore, practically no cohesion 

with the slope and failed chiefly 

by avalanching. 

Many gaping cracks remained 

along the edge of the bluff between 

Point Campbell and Campbell 

Creek after the temblor ceased. 

The sliding, however, was entirely 

superficial and did little to alter 

the firmness of the land surface 

back from the bluff. Nevertheless, by partial removal of the stabilizing vegetative mantle, the vulnerability of the slope to continued 

sapping has been heightened, and 

intermittent sluffing will probably 

take place for a long time to come. 

Slow, gradual backwasting, in 

fact, should be regarded as normal. 

What effect tectonic subsidence-about 2 feet in the Anchorage area-will have on the stability of the bluff line is still undetermined. Certainly the part of the 

bluff near Point Campbell will be 

even more exposed cto the attacks 

of tide and wave than it was before 

the quake. Other points along the 

bluff farther southeast probably 

will be attacked by occasional 

storm waves also, especially when 

strong winds coincide with highest 

tides. It seems likely that, wherever the foot of the bluff is accessible to storm waves, new slope 

profiles will have to be established 

before equilibrium can be fully 

regained. 

POTTER HILL SLIDES 

Destructive slides carried away 

several hundred feet of track and 

right-of-way along The Alaska 

Railroad between mile posts 103 

and 104 about 2% miles northeast 

of Potter (fig. 17). These slides, 

known as the Potter Hill slides, 

were mapped and examined in detail after the earthquake, on April 

20, 1964, by D. S. McCulloch and 

M. G. Bonilla of the U.S. Geological Survey on behalf of The 

Alaska Railroad. The following 

summary is based on their findings. 

The Potter Hill area has a history of landsliding that extends 

back at least 35 years. Bert Wennerstrom, chief accountant of The 

Alaska Railroad recalled that "in 

the late twenties and early thirties, 

heavy rains caused sliding along 

this section (mile 103-104). The 

largest slide took out about 1,000 

feet of track." Wennerstrom remembered that the failures involved cuts in the natural bank 

material (McCulloch and Bonilla, 

written commun., 1964). 

On October 3, 1954, landslides 

caused by an earthquake again 

destroyed trackage in the same 

area. One slump left 140 feet of 

track suspended 15 to 20 feet in the 

air (Miller and Dobrovolny, 1959, 

p. 105). Although it is not clear 

just what materials were involved, 

failure probably occurred in natural bank material as well as in fill. 

The slides of March 27, 1963, 

affected cuts in both natural bank 

material and fill. The ground was 

frozen at the time of the sarthquake and, presumajbly, there was 

little surface runoff. Sand boils, 

however, indicate that the material in the slides had a high water 

content. 

Several kinds of material were 

involved. Glacial till forms the 

top of the bluff back of the slides 

and most of the exposed face of 

the bluff in the northern part of 

the slide area. The till rests on 

outwash with a mnkaut that dips 

gently north. The outwash in 

turn lies on a sequence of blue 

clay, silt, and fine sand, which perhaps is equivalent to the Bootlegger Cove Clay. This sequence 

forms the lower part of the slope. 

At the south end of the slide area, 

a coarse gravel overlies the till. 

The materials in the bluff abut 

against and probably pass beneath 

intertidal silts in the flats at the 

base of the bluff. 

The bluff is saturated at its base, 

and, at several levels above its 

base, ground water escapes laterally through permable beds in the 

outwash. In wells east of the 

slide area, ground-water levels reportedly are 30 to 240 feet above 

sea level. During the earthquake, 

sand spouts issued from cracks 

400 feet east of the edge of the 

bluff. 

All the slides along Potter Hill 

had a similar form. They con- 
ALASKA EARTHQUAKE, MARCH 27, 19 64 

EXPLANATION 

Ground crack 

Bar and ball on downthrown side 

Pressure ridge '1jj 

,iI,,i,,__J 

. . Top of slide scarp I1 

Lllilill 

Bluff line 

A 

Profile from 1916 railroad4 

Mapped on uncontrolled photornosa~c by 

M G Bon~lla and D S McCulloch. Apr~l 1964 

17.-Map and profile of Potter Hill landslide area near Anchorage, Alaska. 

sisted of elongate fragmented 

slump blocks rotated backward 

and broken into many pieces toward the base of the slope. In 

places at the toe, they turned into 

earth and mudflows derived partly 

from the intertidal silt of Turnagain Arm and partly, perhaps, 

from the clay-silt-sand sequence in 

the lower part of the bluff. 

Many pressure ridges formed 

on the flats below the slides; some 

smaller ones were as far as a third 

of a mile beyond the toe, but mast 

of the larger ones were within 400 

feet. They were formed by compmssive stresses probably transmitted horizontally from the toe 

of the slides through the frozen 

upper layers of the estuarine silt. 

Marginal fractures bounded the 

slides r~nghly parallel to the face 

of the bluff. They cut across natural bank material and fill alike 

as high as the level of the tracks, 

in the roadbed itself, and in the 

drainage ditch beside the tracks. 

Near Rabbit Creek, where the 

tracks turn southward across the 

flats, cracks reached nearly to the 

top of the bluff. At one point 

they extended as far back as 400 

feet from the edge of the bluff. 

Sand that was ejected from these 

cracks during the quake spread 

out onto the surface of the snow. 

But in general, cracking was confined to the face of the bluff itself. 

The mechanics of sliding has 

been investigated by D. S. McCulloch and M. G. Bonilla (written 

commun., 1964). They concluded 

that sliding was initiated by failure and flowage of material from 

the base of the slope. Higher 

parts of the slope slumped and 

distintegrated as a consequence. 

Flowage may have occurred in the 

modern estuarine silt at the base 
EFFECTS AT ANCHORAGE A33 

/// Waterline at time of photography' 11- 

Slumped ground 

Ground cracks 

APPROXIMATE SCALE 

18.-Photogeologic sketch map of Point Woronzof landslide area, Alaska. 

of the slope, which carried part of 

the weight of the roadbed, or in 

the fine silt and sand in the lower 

part of the bluff. Perhaps it occurred in both. 

Measurements by McCulloch 

and Bonilla indicate that the volume of the slide material that accumulated at the base of the slope 

and on the adjacent flats was less 

than that of the material removed 

from the slope by sliding. They 

concluded, therefore, that this dif - 

ference in volume was compensated partly by flowage in the 

estuarine silt and partly by lateral 

translation through the silt to 

pressure ridges on the flats. 

SLIDES AT POINT WORONZOF 

Point Woronzof is underlain by 

loose unconsolidated sand and 

gravel. Because it projects north 

into Knik Arm, the point is exposed continuously to the ebb and 

flow of the strong tidal currents 

and to the pounding of storm 

waves propelled across the arm by 

northerly winds sweeping down 

across ihe Susitna Lowland. The 

maximum tidal range at Anchorage is about 38 feet. Point Woronzof, therefore, has been subjected to more or less continuous 

and vigorous shoreline erosion, 

and, since 1909 at least, has retreated southward at a mean rate 

of about 2 feet per year (Miller 

and Dobrovolny, 1959, p. 89). 

Waves and tides, by periodically 

removing sluffed increments of 

sand and gravel from the foot of 

the point, have kept the slopes 

above in a state of precarious repose. It is not surprising, therefore, that on March 27 large volumes of material slumped down 

the face of Point Woronzof under 

the driving force of the earthquake. As shown by figure 18, the 

bluff caved away in three separate 

parts, mostly by modified rotational slumping. The largest 

mass, directly beneath Point Woronzof, extended about 1,500 feet 

along the bluff and about 50 to 100 

feet back behind the old bluff line. 

Part of the slumped mass disintegrated into a debris avalanche, but 

most of it slid down as an intact 

though much fractured block. It 

probably moved very rapidly. 

The next smaller slide was 300 

feet east. It extended about 500 

feet along the bluff and caved back 

about 30 to 40 feet behind the old 

bluff line. It, too, was a much 

fractured but basically intact 

slump. The smallest slide, 150 feet 

farther east, was about 200 feet 

wide. It broke away from the 

slope entirely below the old Muff 

line. 

SLIDES NEAR CAIRN POINT 

Several small landslides were 

generated by the earthquake along 

Knik Arm just south of Cairn 

Point at the west end of Elmendorf 

Air Force Base. Cairn Point, like 

Point Woronzof, projects out into 

Knik Arm and is subject to vigorous erosion by waves and tidal currents. It, too, therefore, has a past, 

history of instability and slumping. 

At Cairn Point an exceptionally 

thick sequence of Bootlegger Cove 

Clay is overlain by silty till of the 

Elmendorf Moraine. The clay is 

at least 126 feet thick, and the till 

is at least 110 feet thick (Miller 

and Dobrovolny, 1959, p. 39). Ths 

quake-induced landslides probably 
A34 ALASKA EARTHQUAKE, MARCH 2 7, 19 64 

19.-Rotational slump near Sleeper landing strip, on the west side of Knik Arm opposite Cairn Point. At its foot, the slump 

passed into an earthflow. Tidewater in foreground. Scarp to left of upper center is about 80 feet high. 

involved both materials, but they 

broke away mostly from the lower 

half of the slope and, hence, were 

mostly in the Bootlegger Cove 

Clay. Morphologically, the slides 

were rotational slumps, modified 

by disruption and flowage. 

The largest slide was about 450 

feet wide at beach line, and it 

surged out at least 200 feet onto 

the tidal mudflat. From its appearance after the quake, it must 

have disintegrated into many 

blocks as it moved downslope, the 

parts that moved farthest disintegrating most completely. At its 

toe, it passed into an earthflow. 

The several other slides, although 

smaller, were identical to the largest in form. 

SLIDnS ON WEST SIDE OF KNIK ARM 

Two large rotational slumps 

were generated by the earthquake 

on the west side of Knik Arm 

about a mile northeast of Sleeper 

landing strip. The larger of the 

two (fig. 19) was just below hill 
EFFECTS AT ANCHORAGE A35 

204 in sec. 35, T. 14 N., R. 4 W. 

(This hill is shown on the U.S. 

Geological Survey 1962 map of 

Anchorage and vicinity.) The 

smaller slide was about a quarter 

of a mile southwest. The Bootlegger Cove Clay rests on glacial 

till at about the level of mean high 

tide, with a contact that appears to 

be gradational. The clay contains 

scattered pebbles throughout, especially near the base; some are as 

large as 4 inches across. 

Bootlegger Cove Clay extends 

nearly the full height of the bluff, 

to an altitude of about 190 to 195 

feet, where it is topped by a veneer 

of sand, silt, and peat. Sliding, 

therefore, was largely in the clay. 

Till may have been involved near 

the foot of the slides, but if so, 

it was pushed out into Knik Arm 

below tidewater. Both slides 

surged out onto the tidal mudflat 

in broad earthflow lobes that 

reached an undetermined distance 

into the water below low tide. 

Before the earthquake, the top 

and slope of the bluff supported 

a forest of birch and cottonwood 

in the slide areas. These trees 

were rotated backward in an arc 

of about 30" to 60°, the angle of 

tilt being progressively greater 

farther downslope. In the mrthflow lobes, many of the trees lay 

flat, their crowns pointed toward 

the bluff and their roots toward 

Knik Arm. 

Detailed land measurements 

have not been made of either slide. 

Estimates based on air and ground 

reconnaissance and on photographs indicate that the larger 

slide was about 700 feet wide along 

the bluff line. It worked headward about 200 feet into the bluff, 

and it surged out perhaps 500 feet 

onto the mudflat for a total length 

of at least 700 feet from crown to 

20.-Block diagram of compound slump near Sleeper landing strip. Two lobes d 

slide surged out onto mudflat below high tide. 

toe. It was a compound slide in 

that it extended back into the bluff 

in two large joined arcu~te alcoves 

(fig. 20). The slide was complex 

in that the slumped mass broke 

into several slices below the crown 

and into countless jumbled blocks 

toward the foot, where it passed 

into an earthflow. Its main scarp 

had a pronounced concave-outward profile and a maximum 

height of about 80 feet from the 

crown to the jumbled blocks below. 

The smaller slide was similar to 

the larger one in morphology and 

habit, but its main scarp formed 

a simple arcuate alcove about 90 

feet high. Gouging and slickensides on the face of the soarp indicate that the slumped mass slid 

diagonally downward from upper 

left to lower right (as viewed from 

the crown) rather than directly 

down the fall line ; the reason for 

the diagonal slipping is unclear, 

unless the mass slumped almost 

instantaneously land at the same 

time lurched laterally in response 

to the ground motion of the quake. 

The slumped mass itself was rotated backward toward the bluff, 

but it was broken into helter-skelter blocks in various attitudes of 

disarray, particularly out toward 

the toe. 

Near the foot of the smaller slide 

there were sand boils 3 to 4 feet 

high. Because the bluff had only 

a thin veneer of sand at the top, 

the boils presumably were derived 

from the subjacent beach. 

The slip plane of an older slide 

was exposed in section on the south 

side of the main scarp of the 

smaller slide. The older slide-no 

longer preserved as a topographic 

form-was truncated by the slip 

plane of the younger one. 

Further slumping at a gradually diminished rate is forecast for 

both slides. The toes of both slides 

project far out into Knik Arm 

where they are under relentless attack by tidal currents and waves 

and where removal of material 

will reduce whatever buttressing 

effect may have existed immediately after the quake. Loss of buttress support, in turn, will encourage further rotation of the main 

slide masses ; this rotation will remove support from the main 

scarps. These scarps already are 

precarious, .and will remain so until headward slumping has reduced their height and pitch to 

a more stable configuration. In 

brief, therefore, erosion at the toes 

and slumping at the heads will 

continue indefinitely at a gradually diminishing rate until something approaching the prequrake 

profile of the bluff has been restored. 
A36 ALASKA EARTHQUAKE, MqRCH 27, 1964 

21.-Chaotic pressure ridge at toe of rotational slide, Bluff Road.. In part, toe surged forward as an earthflow. Compare 

with flgure 22. 

ROTATIONAL SLIDES ALONG BLUFF 

ROAD 

Several rotational slides gave 

way along the south-facing bluff 

between the district offices of the 

arps of Engineers and the steam 

generating plant of Elmendorf 

Air Force Base. About 1,300 feet 

line of Ship Creek, between Bluff of bluff gave way in a compound 

Road and the tracks of The displacement consisting of four 

Alaska Railroad (fig. 1). The separate but connected slumps. 

most widespread failure in that Collapse at the heads of the 

area extended east along the bluff slumps extended back horizontally 

into the bluff as much as 120 feet. 

An additional 400 feet of bluff line 

east and west of the main slide 

mass cracked and began to slump. 

Altogether, about 650 feet of 

Bluff Road was destroyed, dropping as much as 40 feet below the 

prequake gradeline and rotating 

backward 15" to 30". 
EFFECTS AT ANCHORAGE 

N 

In old gravel fill. 

but clay crops out 

about 9 feet above Bootlegger Cove Clay railroad grade in 

Bootlegger Cove Clay nearby undisturbed bluffs Inferred failure surface 

Approximate mean sea level 

0 50 100 150 FEET 

All four slumps were modified 

by mulkiple cracking, internal 

breakup, and flowage. None 

moved as a simple block. Within 

each slump, slices rotated on individual slip surfaces, their motions modified by interference or 

shoving of one slice against another. !l%ere was evidence, moreover, of flowage beneath each 

slump, as well as of extrusion of 

material at the toe. 

At the toe, each of the four 

slumps bulged out into a chaotic 

ldbe of jumbled blocks (fig. 21). 

These lobes were transitional in 

form between pressure ridges and 

earthflows. Three of them stopped short of The Almaska Railroad 

tracks; the most easterly lobe, 

however, advanced across two sets 

of tracks, but wikhout damaging 

the tracks or the roadbed. Each 

slump had a length of about 300 

feet from crown to toe. 

In general, the rotation of 

blocks within the slides diminished downslope from the head of 

each slide toward a position about 

halfway down, below which rotaAPPROXIMATE SCALE 

22-Sketch section through rotational slide at Blufe Road. 

tion either increased again or the 

attitude of the blocks became chaotic (fig. 22). In other words, the 

old ground surface was tilted most 

near the head and least $bout 

halfway to hhe toe. This differenkial tilting (in addition to rotation) seems to have been in response .to a withdrawal of material 

from beneath the headward parts 

of the slumps, either by flowage 

and extrusion, by lateral spreading, or by a combination of the 

two. If by a combination, these 

slides represent a transitional form 

between the simple slumps of the 

Point Woronzof and Cairn Point 

areas and the block-glide displacements in the downtown Anchorage area. 

Most of the visible landslide 

material was coarse o u t w a s h 

gravel. Some of it had been disturbed prior to the quake, and 

some plainly had been backfilled 

artificially. Bootlegger Cove Clay, 

however, was exposed along a line 

of springs 9 feet above the base of 

the slope of the bluff just west of 

the slides, and it must have 

extended into the slide area. Its 

loss of strength under the vibratory motion of the quake very 

likely contributed to the failure of 

the slope and to the flowage at the 

toes and beneath 'the heads of the 

slumps. 

East from the steam generating 

plant, cracks and smaller separate 

slumps extended along the bluff a 

total distance of about 3,000 feet. 

The bluff beyond was appreciably 

lower and presumably more stable. 

Some of these slumps showed clear 

evidence of movement prior to the 

March 27 earthquake, particularly 

the slump just east of the steam 

plant and the one in the next bend 

of Bluff Road farther east. Old 

settlement cracks in the road at 

these places had been filled and 

patched before the quake. 

Emergency repairs along Bluff 

Road did little to stabilize the sliding triggered by the quake. These 

repairs consisted simply of backfilling collapsed areas with gravel 

to reestablish the grade profile, 

without regard for the unbalancing effect that the backfilling 
A38 ALASKA EARTHQUAKE, MARCH 2 7, 19 64 

might have on the slide itself. At 

several points along the bluff, fill 

material dumped onto the slides 

probably caused continued movement by overweighting the head 

and altering whatever balance had 

been achieved naturally. By midMay of 1964, new cracks with small 

vertical displacements had already 

formed in the repaired fills. Unless remedial procedures are altered, therefore, continued slow 

movements at the heads of the 

slumps seem inevitable. A comprehensive stabilization program 

for these slides, on the other hand, 

may be less feasible economically 

than intermittent road repair and 

maintenance, 

TRANSLATORY SLIDES 

All the highly destructive landslides in the built-up parts of Anchorage were of a single structural-dynamic family, d e s p i t e 

wide variations from slide to slide 

in size, appearance, and complexity. All moved chiefly by 

translation rather than rotation. 

They slid laterally on nearly horizontal slip surf aces following drasCic loss of strength in previously 

weak sensitive zones of the Bootlegger Cove Clay. Slides in which 

the slid mass was practically intact 

are classed as block glides; those 

in which the slid mass underwent 

appreciable disruption are probably best classed as failures by 

lateral spreading (Varnes, 1958, 

pl. 1). Between these limits, all 

gradations of form were represented-not only from place to 

place but also in time. Structurally, the Fourth Avenue slide was 

the simplest and the Turnagain 

Heights slide was the most complex. The Turnagain Heights 

slide, however, must have begun as 

a simple though highly transient 

block glide, or perhaps as several 

such block glides, arising independently along the bluff line. As 

sliding progressed, the Turnagain 

Heights slide deteriorated rapidly 

into a complex failure involving 

simultaneous motions in several directions. Its predominant motion, 

however, remained translatory. 

Destruction to property in the several slides was caused by tilting, 

wrenching, warping, and disruption of structures over the cracked, 

collapsed, and compressed zones of 

the slides. Structures in undistorted parts of some slides were 

little damaged despite horizontal 

ground translations of several feet. 

Translatory slides are less common than rotational slides. They 

have, therefore, received less attention in the literature. Examples similar in many respects to 

those at Anchorage, however, have 

been reported and described from 

Scandinavia where the Pleistocene 

history has been comparable in 

some ways to that at Anchorage. 

Notable translatory slides occurred at Skottorp, Sweden, in 

1946 (Odenstad, 1951) and at Bekkelaget, Norway, in 1953 (Eide 

and Bjerrum, 1955, p. 88-100; 

Rosenqvist, 1960, p. 10). The 

Skottorp slide, particularly, resembled the Turnagain Heights 

slide, except that it was smaller; 

the Bekkelaget slide was similar to 

the Fourth Avenue slide. Translatory slides in the conterminous 

United States somewhat like those 

in Anchorage have been described 

by Crandell (1952, p. 552; 1958, 

p. 73) and by Varnes (1958, p. 26- 

32). All these slides-in Scandinavia and in the United Statesmoved in response to gravitational 

stress, without the intervention of 

earthquakes. 

Earthquake-triggered landslides 

accompanying the great New 

Madrid, Mo., earthquakes of 1811 

seem to have been very similar to 

the slides at Anchorage. The 

physical setting of the slides was 

analogous to that at Anchorage. 

Fissures, sand blows, and various 

other features related to sliding 

are described by Fuller (1912, p. 

48, 59-61) on the basis of early 

accounts and on observations made 

nearly 100 years after the quakes. 

Puller's descriptions might well 

apply to the Turnagain Heights 

slide. Grabens and tension cracks, 

for example, were formed where 

clayey alluvium, afloat on quicksand, glided laterally. 

The Chilean earthquake of May 

22, 1960, triggered three large 

landslides at Lago Rifiihue, 65 

kilometers east of Valdivia in central Chile. The descriptions of 

Davis and Karzulovic (1963, p. 

1407) indicate that these slides resembled the Turnagain Heights 

slide in form, size, and mode of 

failure. Translatory movement 

predominated ; rotational movement was subordinate. Significantly, these slides occurred in an 

area of previous landsliding and 

were partly superimposed on preexisting landslides. 

GEOLOGIC SETTING 

All areas of translatory sliding 

in Anchorage had the same general 

geologic environment. All were 

underlain at various depths by 

Bootlegger Cove Clay that had 

zones of low shear strength, high 

water content, and high sensitivity. 

All surmounted flat-topped bluffs 

bounded on one side by steep 

slopes. In all areas, except the 

westernmost part of the Turnagain Heights slide, the Bootlegger Cove Clay was overlain by 

outwash sand and gravel. These 

deposits thinned markedly over a 

distance of a few miles from north 

to south and from east to west; 

grain size diminished concomitantly from gravel to sand. Near 

the Alaska Native Service Hospital the outwash is about 55 feet 

thick, n e a r Government Hill 
School about 40 feet, in the downtown area about 30 to 40 feet, and 

at Turnagain Heights from about 

25 feet to zero. 

Outwash deposits had no critical part in the sliding. Failure 

was confined to thin zones of sensitive clay, silt, and sand within 

the Bootlegger Cove Clay. 

Several geologic factors acting 

in concert with earthquake shaking probably caused failure in the 

several slide areas. All these factors are themselves variables at 

each site. They include: (1) the 

topographic elements of bluff configuration-the height of the bluff 

above its base, the slope angle or 

declivity of its face, and perhaps 

the ground-plan configuration, 

(2) the soil-strength profile, including consistency, dynamic shear 

strength, and sensitivity, and (3) 

water content and liquid limit of 

the soil at the critical depth below 

the ground surface. Some of 

these factors seem to be interdependent-the height, slope, and 

ground-plan configuration, for 

example, may have influenced the 

water content of the soil, which in 

turn influenced the consistency. 

The influence of topography, 

particularly the bluff profile, on 

failure susceptibility seems obvious. The ultimate driving force 

of landsliding was gravity, operating on a nearly horizontal shear 

surface in the direction of least 

shear resistance (the free face of 

the bluff) and acting on a dynamically sensitive soil that had undergone a severe loss of strength by 

earthquake shaking. Other factors being equal, the higher and 

steeper the bluff profile, the greater 

is the shearing stress, the less effective is the shear resistance of the 

clay, and the greater is the susceptibility of the bluff to failure. 

The full significance of groundpl,an configurartion is uncertain 

slip plane 

Stable slope 

Failed 

60.13 

"Nors" 

d/H ratio shown 

HEIGHT OF SLOPE (H), IN FEET 

23.-Slope stability chart. Reprinted from Shannon and Wilson, Inc. (1964, pl. 7.1). 

and may involve several variables 

difficult to evaluate. Most failures took place along fairly 

straight or recessed bluff lines, for 

reasons not entirely clear, although possibly because such 

.places are apt to be well watered 

(Shannon and Wilson, Inc., 1964, 

p. 33). Salients or cuspate areas 

("noses") generally were spared 

failure, again possibly because 

they are apt to be well drained, 

although the slide at the Native 

Hospital failed precisely at just 

such a salient. 

Using factors of height and 

slope, only, Shannon and Wilson, 

Inc. (1964, pl. 7.1), constructed a 

slope stability chart that grouped 

failed and stable slopes and 

showed lower limits of slope-toheight ratios below which failure 

is improbable (fig. 23). The 

higher the slope, the flatter the 

angle at which the slope is susceptible to failure, other variable 

factors such as soil strength and 

water content being equal. The 

fact that several stable slopes, including salients or "noses," have 

slope-to-height ratios within the 

same area of the chart as slopes 

that failed seems to point up the 

modifying influences of other factors such as soil-strength profile 

and water content. A low slope 

underlain by soil having a high 

water-plasticity ratio, for example, may be more susceptible to 

failure-may have a lower safety 

factor-than a high slope underlain by soil having a low waterplasticity ratio. In a unit of time, 

other factors being equal, a salient 

should drain and desiccate more 

rapidly than a recess; hence it 

should be more stable. 

The length of time a bluff has 

been stationary and unmodified by 

erosion may perhaps influence its 

dynamic stability by affecting the 

water content of the underlying 

Bootlegger Cove Clay. Far more 

information on the water content 

of the clay at critical localities 

than is now available would be 

needed to test this hypothesis, but 

presumably a long-stationary bluff 

line would have a better chanee 

of desiccation, and hence of 
ALASKA EARTHQUAKE, MARCH 2 7, 19 64 

- Head24.-Block diagram of a translatory slide. 

dynamic stability, khan an actively 

retreaking one. Permeability is 

extremely low in most of the 

Bootlegger Cove Clay, and a long 

period of immobility would be required to promote even a low degree of drainage and desiccation. 

At Turnagain Heights, for example, the bluff line facing Knik 

Arm, which failed so dramatically 

during the earthquake, was in a 

state of relatively rapid regression owing to adive shoreline 

processes prior to the quake, 

whereas the bluff line facing Fish 

Creek was relatively stationary 

before the quake and did not fail 

during the quake. 

GEOMETRY AND MODE OF FAILURE 

Translatory slides of the Anchorage area varied widely in size, 

shape, ,and internal complexity, 

but they all conformed to a single 

basic geometric format. Figure 

24 is a simplified block diagram 

showing the essential structural 

elements, including the head, toe, 

bluff line, slip surf ace, graben, and 

pressure ridge. Sections through 

both the Fourth Avenue and the 

L Street slides closely sapproximate the idealized section at the 

front of the block diagram. The 

so-called slip surf ace probably is 

not generally a surface at all, at 

least at the onset of sliding, but 

rather is a narrow planar zone of 

failure. 

Geometric development of the 

translatory slide is reconstructed 

in the following sequence: Earthquake shaking drastically reduces 

the shear strength of saturated sensitive zones in the Bootlegger Cove 

Clay. The strength of the clay 

falls below the level of shear strbss 

caused by the weight of material 

in the bluff and the accelerations of 

the quake. Under the influence of 

gravity, therefore, a prismatic 

block of earth begins to move laterally on a nearly horizontal slide 

surface toward the free face of the 

bluff. In effect, the block is afloat 

on a zone of disturbed clay whose 

drength properties are those of a 

confined viscous liquid. As the 

block starts to move, tension fractures form at the head of the slide 

and widen as movement progresses. These tension fractures 

dip toward the slide block at commonly observed angles of about 

60" to 70°. As the fractures widen, 

their hanging wall (on the moving 

block) loses support and collapses 

along one or more antithetical 

fractures to form a graben. 

The term "graben," since the 

earthquake, has become a household word to the populace of Anchorage. The downward pistonlike movement of the graben is 

synchronous with the lateral slippage of the slide block. Continued 

slippage places more ground under tension behind the slide, and 

additional fractures form as the 

slide retrogresses headward. In 

the more complex slides such as the 

Government Hill slide, and, es- 
E,FFECTS AT ANCHORAGE, 

pecially, the Turnagain Heights 

slide, this process occurred repeatedly, and a series of alternate 

horsts and grabens developed regressively, parallel to the direction 

of slippage. (See figs. 37,44, and 

pl. 2). 

As the block moves outward, 

tension at the head of the slide is 

partly countered by compression at 

the toe, and pressure ridges form 

in the flats below. This step may 

be transient, because continued 

compression leads to rupture and 

overthrusting. Both steps occurred in each of the translatory 

slides and caused extensive local 

damage. The Turnagain Heights 

slide not only sheared off at the toe, 

but it slid under gravity down the 

mudflat into Knik Arm-at one 

point it slid more than half a mile. 

But if resistance in the toe builds 

up to a level equal to the thrust of 

the moving block plus the shear resistance of the clay at the slip surface, motion will stop. A modification of this principle was utilized by the Corps of Engineers 

in designing remedial buttresses. 

The Corps, however, visualized the 

driving mechanism of the slide as 

the "active earth pressure" of the 

earth mass behind the head of the 

slide (Shannon and Wilson, Inc., 

1964, p. 32) plus the acceleration 

of earthquake ground motion. But 

inasmuch as the head of the slide 

block is plainly under tension during sliding, there obviously can be 

no "active earth pressure" from the 

mass behind it. Furthermore, inasmuch as regression and sliding 

continued after earthquake ground 

motion had ceased (p. AM), the accelerations of the quake cannot be 

the driving mechanism either. 

Rather, sliding was precipitated 

by gravity as soon as the accelerations of the quake had reduced the 

shear resistance of the soil to the 

point of failure. The earthquake 

was the L'ltrigger" ; graviky was 'the 

"propellant." Sliding continued 

as long as the gravitational component on the sliding surface exceeded the shear resistance of the 

soil. At Turnagain Heights, sliding probably continued a full minute or more after earth shaking 

had stoppd (see page A64). 

In plan, each slide was bounded 

laterally by a series of crescentic 

tension fractures, which also 

marked the outer wall of the 

outermost graben. Subordinate 

crescentic tension fracturesbounding potential slide blockscommonly extended headward, 

outside the slide proper, scores or 

hundreds of feet beyond the 

bounding fractures. At Turnagain Heights, numerous crescentic tension fractures extended back 

through the subdivision as much 

as 2,200 feet beyond the head of 

the slide (pl. 1) ; had the earthquake lasted longer, sliding undoubtedly would have retrogressed 

back into that area. "Retrogression," as applied to landslides, 

means a headward expansion of 

the slide. (See Vanes, 1958, p. 31.) 

Extensive internal fracturing 

also characterized all slides, although internal fracturing was 

minimal in the L Street slide. The 

Native Hospital slide contained 

abundant radial fractures; as 

noted before, this slide occupied a 

salient or '<nose" on the bluff line, 

and the radial fractures undoubtedly were tensional responses to 

lateral spreading. 

THE GRABEN RULE 

A close approximation of the 

depth of failure is prerequisite to 

planning remedial or stabilization 

procedures. A significant geometric relationship, here called the 

"graben rule," affords a rapid, yet 

relitable, estimate. The pben rule 

should apply to any translatory 

slide in which flowage of material 

from the zone of failure has not 

been excessive. Because the crosssectional 'area of the graben trough 

approximates the cross-sectional 

area of the space voided behind the 

block as the block moves outward, 

the depth of failure can be estimated from the simple relationship D = A/I where D is the depth 

of failure, A is the cross-sectional 

area of the graben, land 1 is the lateral displacement of the block. 

For example, the Fourth Avenue 

graben, on the average, was about 

11 feet deep, 100 feet across, and 

had an area (A) of about 1,100 

square feet. Its maximum lateral 

displacement (1) was about 17% 

feet, as determined by postquake 

resurveys. The calculated depth 

of failure (D) was about 63 feet, 

or about 43 feet above mean sea 

level. Subsurface exploration, 

though somewhat indecisive in its 

results, yielded a nearly identical 

figure. 

INDIVIDUAL TRANSLATORY LANDSLIDES 

Fourth Avenue Slide 

The Fourth Avenue slide involved all or parts of 14 city blocks 

in a roughly oval area of about 36 

acres, containing perhaps 2 million cubic yards of earth, centered 

at the north side of downtown Anchorage (fig. 25). It was bounded 

headward on the south by Fourth 

Avenue, on the west by E Street, 

on the north approximately by 

First Avenue, and on the east 

somewhat indefinitely by Barrow 

Street. Its length north to south 

in the direction of slippage was 

about 1,050 feet; east to west it was 

about 1,800 feet across. Strong 

fracturing and related ground displacements extended 1% blocks 

(about 450 feet) or so south of the 

slide proper, where considerable 

damage was inflicted on buildings, 
A42 ALASKA EARTHQUAKE, MARCH 2 7, 1964 

EXPLANATION 

data taken from reports of cnglneerlng 

Geology Evaluat~on Group (1964) and 

Shannon and Wilson, Inc, (1964) 

Fracture, showing downthrown Graben Lateral displacement of 

side and displacement in feet bench mark, in feet. 

11111,1111 111,11,118,,18, ,,,, New position at point 

Pressure ridge of arrow. No appreciable movement since 

earthquake 

25.-Fourth Avenue landslide area, Anchorage, Alaska. 

streets, and sidewalks. Minor dis- Plafker, and Kachadoorian, 1964, Fourth Avenues in the west part. 

placements extended as far south p. 15). North from those areas, downas 600 feet. Eyewitnesses re- Most of the damaging tensional slope, compressional movements in 

ported that sliding began about 2 fractures within the slide mass the foot of the slide caused numerminutes after the earthquake were between Second and Fourth ous pressure ridges. 

started and stopped about the same Avenues in the east part of the Ground dislocations were most 

time as the earthquake (Grantz, slide and between Third and severe in the graben areas at the 
EFFECTS AT ANCHORAGE 

head of the slide along the north 

side of Fourth Avenue (fig. 4). 

Ironically, these areas also had 

the highest property evaluations. 

Many small business and commercial buildings, apartment houses, 

and residences were destroyed or 

badly damaged. Vacant lots and 

parking spaces within the slide 

block to the north were little disturbed. Just east of C Street the 

main graben bifurcated, and two 

long belts of severe damage extended northeast toward Barrow 

Street. 

Between B and D Streets, where 

the destruction was total, the main 

graben had a width of 100 to 150 

feet and a depth of as much as 11 

feet. Lateral displacements near 

the center of the slide just north of 

the graben were as much as 17% 

feet toward the north, according 

to surveys by the City Engineer's 

office. Near the foot of the bluff 

on Second Avenue a block east of 

B Street, a complex of pressure 

ridges was pushed up by 19 feet 

of lateral displacement-apparently the greatest local slippage 

in the slide. Although several 

days elapsed after the quake before 

resurveys were started, there appears to have been no movement 

since the main quake. None of the 

strong aftershocks caused measurable movement. 

Subsurface exploration of the 

Fourth Avenue slide was started 

by the Engineering Geology Evaluation Group soon after the earthquake, and was expanded and 

concluded by the Corps of Engineers. The findings of these 

groups indicate that failure occurred at the top of the sensitive 

zone of the Bootlegger Cove Clay 

at a depth of about 60 feet (48 

feet above mean sea level). Additional failures may have occurred at greater depths, inasmuch 

as many pressure ridges formed 

at the surface in the toe of the 

slide at altitudes below 48 feet, 

unless, as suggested by their 

sharply peaked crests and steep 

sides (fig. 26), the ridges were 

caused by simple surface translations of the rigid frozen surface 

layer of the soil. 

Shear-strength profiles measured near the head of the slide 

by Shannon and Wilson, Inc. 

(1964, p. 41) show that the clay 

decreases in strength from about 

1.0 tsf at altitude 70 (top of clay) 

to as low as 0.25 tsf between altitudes 45 and 20, then increases in 

strength to about 0.75 tsf at 15 

feet below sea level. The zone of 

maximum sensitivity coincides 

with the zone of minimum 

strength, and failure appears to 

have followed spontaneous liquefaction of sand layers as well as 

loss of strength in silty clay. 

L Street Slide 

The L Street slide involved all 

or parts of about 30 city blocks in 

the northwest part of Anchorage 

adjacent to Knik Arm (fig. 27). 

It extended northeast about 4,800 

feet along the bluff and had a 

maximum breadth northwest 

across the bluff of about 1,200 feet, 

parallel to the direction of slippage. It reached about a block 

and a half back from the bluff 

line into thickly sektled residential 

and commercial neighborhoods of 

Anchorage. In all, about 72 acres 

were included between the graben 

at the head of the slide and the 

outermost pressure ridges at the 

toe. The total volume probably 

approached 6 million cubic yards 

though an accurate estimate is difficult. Much of tlle 72-acre area, 

however, was little if at all damaged, despite lateral shifting of as 

much as 14 feet. Most of the 

damage was concentrated along 

the graben, which with marginal 

fractures covered about 14 acres, 

and $along $he pressure ridges, 

which were mainly linear features 

but which involved properties of 

a total area of perhaps 7 70 8 

acres. There was very little fracturing much beyond the bounding 

fractures of the graben, and there 

was not much fracturing within 

the slide mass itself except for the 

graben area. Eyewitness reports 

indicate that slippage began during the latter part of the earthquake (Shannon and Wilson, Inc., 

1964, p. 53). 

The whimsical pattern of destruction in Anchorage was perhaps best exemplified by the L 

Street slide; here wrecked buildings inside or astride the graben 

faced almost undamaged adjacent 

properties on either side (fig. 28). 

The irregular trends of the bounding fractures further compounded 

the fateful selectivity of the slide. 

Damage was equally capricious, 

moreover, in the compressed areas 

at the toe of the slide; here individual dwellings were buckled or 

shoved by pressure ridges that as 

often as not left adjoining buildings undisturbed (fig. 29). 

The graben itself formed a 

broad arc in plan, concave toward 

the slide block. It extended south 

from West Third Avenue between 

K and 1, Streets and curved westward to R Street between Ninth 

and Tenth Avenues. It was about 

3,600 feet long and had a maximum width of about 250 feet ; generally, its width was between 150 

and 200 feet (fig. 30). Its depththat is, the displacement of the 

down-dropped block-reached a 

maximum of about 10 feet; the 

displacement was greater south of 

Sixth Avenue than north. Overall, the graben looked like a dry 

canal or a streambed, and, when 

contrasted with the lack of damage 

on either side, it stirred considerable speculation in the minds of 

early viewers. One popular magazine account stated that it resulted from collapse of an old 
A44 ALASKA E.ARTHQUAKE, MARCH 2 7, 19 64 

26.-Sharp-crested pressure ridge at Second Avenue and C Street, Anchorage. Probably caused by shallow translation of frozen 

surface layer. Note smaller pressure ridge in street part way up block and toppled chimney of building behind car. Photograph 

by Mac's E'oto, Anchorage. 
E.FFECTS AT ANCHORAGE A45 

EXPLANATION 

Pressure ridge -- 

4- 

Lateral displacement (feet) 

Line of geologic section 

Base by c~ty of Anchorage Based on data prov~ded by 

Off~ce of Cty Engtneer Englneer~ng Geology Evaluation 

0 400 800 1200 FEET Group, Anchorage (1964) 

27.-L Street slide area, Anchorage, Alaska. Geologia cross sections are shown in figure 30. 
A46 ALASKA EARTHQUAKE, MARCH 27, 1964 

28.-Wrecked dwelling astride boundling fracture, L Street graben at Eighth Avenue ar,d N Street. Damage caused 

entirely by ground displacement along fracture. 
EFFECTS AT ANCHO,RAGE A47 

29.-House pushed off foundation by pressure ridge at toe of L Street slide. Well-framed house not otherwise 

visibly damaged. Push must have been shallow and nearly horizontal. 

buried but melted-out ice-filled 

channel ! 

Many buildings on the slide 

block, including a six-story apartment building carried 10 feet laterally, sustained little or no damage, but utility service to the slide 

block was curtailed. Overhead 

wires and buried water, gas, and 

sewer lines all were disrupted 

where they crossed the graben. In 

most places, entirely new emergency connections had to be made 

before service could be restored. 

Many buildings, therefore, which 

were not themselves damaged 

were nevertheless evacuated. 

Pressure ridges below the slide 

block were concentrated mostly in 

a zone about 200 feet wide close 

to the foot of the bluff at 40 to 55 

feet above sea level (figs. 27, 30). 

A fern- extendecl beyond The 

Alaska Railroad tracks, which 

were damaged by lateral shove, 

and even onto the ticlal flat of Knik 

Arm about 500 feet from the foot 

of the bluff and only about 15 feet 

above mean sea level. Individual 

ridges ranged in length from a few 

tens of feet to more than 600 feet. 

They ranged in ~ridth from 

sharply peaked ridges 10 to 15 feet 

across to broad gentle budges sev 

era1 tens of feet across. Most were 

less than 3 feet high, but a fen- were 

as high as 7 feeit. Xany were ruptured and overthrust toward Iinik 

Arm. 

Tlie available evidence, both surface and subsurface, favors the 

view that the pressure ridges were 

caused chiefly by shallow compressioiial translations of the frozen 

superficial soil mantle, which in 

turn was shoved laterally by the 

sliding block behind. This mantle 

\\-:-as only a few feet thick, but it 

vTas highly competent in its frozen 

state. Some indication of its 

strength \\-as provided at one point 

11-liere a small chunk of partly 

buried concrete caught in a surface 

fracture was so firmly held in place 

that it parted in half instead of 

breaking free from the frozen soil. 

In further support of the shallow 

depth concept, the altitude of the 
A48 ALASKA EARTHQUAKE, MARCH 27, 1964 

SEA I 

- A 0 Halrflne I/ fractures 

100 - 

4 C 

A' 

C 2 

9th Ave 3 E r VI a 

. CI E 

a 

t 

Swale A-22 - 

Clay (wet) Hummocky- 40' 

'inferred zone of fa~lure 

Soft sensltlve clay 

.EVEL 

House projected 

into line of section 

and foreshortened 

B Canted blocks 

100' of sod G 

B ' 

Log house projected 

Into llne of sect~on 

80' (Fireplace and chrmn 

mostly collapsed) 

60' 

40' 

----- 20' 

Possible old 

slide block 

100' 

80' 

60' 

40' 

20' 

SEA LEVEL 

0 50 100 150 FEET 

30.-Geologic section through the L Street slide. In seation C-C' the toe of the slide is to the right of C'. 

pressure ridges above sea level was 

very close to the inferred altitude 

of failure beneat,h the main slide 

block. 

Damage caused by pressure 

ridges was extensive in the L 

Street slide 'although it was generally less devastating and less 

spectacular than that caused by 

tensional cracking and displacement in the graben area. Even so, 

losses to many small dwellings totaled thousands of dollars; more 

expensive losses were sustained by 

larger structures. Some buildings 

that showed little evidence of damage on the outside sustained severe 

structural damage within. Utilities were badly damaged also. 

Subsurface exploration of the L 

Street slide, as of the Fourth Avenue slide, was sbarted by the Engineering Geology Evaluation 

Group soon after the earthquake, 

to learn the causes of sliding, to 

predict future behavior of the 

slide, and to recommend courses 

of action to be taken by the city. 

Subsequently, this work was transferred to the Corps of Engineers. 
Extensive drilling and sampling 

by the Corps, a~~gmentnted by surface studies, indicated a complex 

and varied stratigraphy, modified 

by erosion downslope from the 

bluff line and by prior landsliding 

of undetermined age. Shannon 

and Wilson, Inc., (1961, p. 54) reported the following general sequence of stratigraphy : 

1. At the top, outwash sand and 

gravel, generally 40 to 60 feet 

thick. 

2. Stiff, silty clay, about 30 to 50 

feet thick, and interbedded 

layers of sand and silt. This 

clay had a static shear 

strength generally greater 

than 0.5 tsf. 

3. Silty clay, sensitive, 20 to 30 feet 

thick, having very sensitive 

layers of clayey silt, silt, and 

fine sand. Static shear 

strengths ranged from about 

0.2 tsf to more than 0.5 tsf, 

and sensitivity ranged from 

about 5 to 30. 

4. Stiff silty clay containing scattered sand grains, pebbles, 

and lenses of sand; thickness 

undetermined but greater 

than 50 feet. Static shear 

strength in this unit generally 

exceeded 0.5 tsf and increased 

with depth. 

Despite numerous borings, the 

position of the zone of failure in 

the L Street slide was not definitely 

established, although zones of very 

low strength and high sensitivity 

were clearly indicated. Presumably, slippage occurred at the top of 

the sensitive zone, where the 

strength was lowest and the shearing stress was highest (Shannon 

and Wilson, Inc., 1964, p. 55). 

This position varied appreciablyfrom about 55 to 85 feet below 

ground surface (45 to 15 feet above 

sea level) -in different drilling locations. Estimates based on the 

graben rule place the zone of failure within that range also. Pressure ridges at the foot of the slide 

lie within the same range of altitudes. Therefore, if failure beneath the block IT-as ~vitllin that 

range, the pressure ridges-as 

noted above-must have been 

caused by shallom- translations of 

the relatively thin frozen surface 

layer-a sort of shove effectrather than by deeper surfaceward 

shear. If so, some of the remedial 

buttresses proposed by the Corps 

of Engineers (Shannon and TTilson, Inc., 1964, pl. 9.6) would require design changes to be effective 

in the event of future movement. 

Failure by liquefaction may also 

have occurred in saturated sand 

layers within the clay because several such layers were penetrated 

during the drilling program. Remolding would not necessarily lead 

to strengthening of these sand layers, unless repacking led to consolidation accompanied by escape 

of excess pore water. Unless these 

strengthening conditions h a v e 

been met, the sand could fail again 

under similar circumstances as 

before. 

Native Hospital Slide 

The Native Hospital slide, or 

First Avenue slide as it has occasionally been called, disrupted part 

of the grounds of the Alaska Kative Service Hospital and wrecked 

a fuel-storage tank at the foot of 

the bluff (figs. 31, 32). Although 

it was a small slide and not a very 

destructive one, it was of unusual 

scientific interest because of its 

clear portrayal of repeated translatory landsliding in the same area. 

The slide of March 27, 1964, transected an earlier slide of identical 

habit and exposed the older graben 

in full cross section (fig. 32) in the 

headward scarp of the present graben. This site of failure, therefore, seems to answer the question 

Inasmuch as First Avenue does not extend into this part of Anchorage, the name 

"First Avenue slide" is misleading. 

as to whether natural remolding 

and consolidation of the clay after 

sliding is sufficient in itself to forestall further sliding-it obviously 

was not, in the Native Hospital 

slide. Most other slide areas at 

Anchorage and vicinity also presented evidence of multiple sliding, but none did it as clearly ss 

the Native Hospital slide. Multiple sliding is discussed further on 

pages A66-A67. 

The Native Hospital slide involved only slightly more than 4 

acres of ground and perhaps 360,- 

000 cubic yards of earth. From 

flank to flank-northwest to southeast-it mas about 650 feet across; 

from head to toe it was about 350 

feet. Most of the disruption was 

in the slopes of a cuspate salient 

on the bluff line behind the hospital, but about three-fourths of an 

acre of upland behind the hospital 

collapsed into the graben as the 

main headward fracture opened up 

120 feet or so back from the rim. 

Part of the parking lot of the hospital and an area of lawn-covered 

grounds were destroyed. Fractures that extended back from the 

slide damaged the hospital building itself. 

The graben was exceptionally 

large for the size of the slide. Its 

disproportionate size is attributed 

to the large apparent lateral slippage of the slide. Arcuate in 

plan, it was about 600 feet long; 

it had a mean width of about 120 

feet and a downthrow (depth) of 

as much as 25 feet which averaged 

about 20 feet. Its depth diminished rapidly toward the south, 

where horizontal slippage died out 

also. 

Near the center of the slide, the 

downdropped graben wedge broke 

off precisely at lthe bluff line and 

tilted headward as it collapsed, so 

that the displacement at the headwall of the graben was greater 

than at the front wall and gave 
ALASKA EARTHQUAKE, MARCH 2 7, 1964 

I 

Topography sterocompiled by J. R. Helm, 

U .S. Geolog~cal Survey 

Graben indicated by shading 

31.-Native Hospital slide area, Anchorage, Alaska. Graben indicated by shading. 
32.-Air view (looking south) of Kative Hospital slide showing graben and pressure ridge. The scar of an older landslide 

is transected by the slide of March 27, 3964. Photograph by U.S. Army. 
ALASKA EARTHQUAKE, MARCH 2 7, 1964 

Old graben of S1ightly hummocky Graben of present k earlier slide 4 bed^^^^^^^ w' i, I/ 

slide 4 

120' Slickensides 

rojected centerline of 

100' 

80' 

60' 

40' 

20' 

trees 

SEA LEVEL I I I 

E Cottonwood 120' 

100' 

Road on possible 

80' old slump block 

60' 

4 0' 

20' ferred zone of failu 

SEA LEVEL 0 0.1 0 40 

Shear strength Sensitivity 

(tons per sq ft) (0-40) 

Boring E102A 

(Shannon and Wilson, lnc.,1964) 

0 50 100 150 FEET 

IIIIII I I 

33.-Geologic sections through the Native Hospital slide, Anchorage, Alaska. Section D-D' transects the graben of an earlier 

landslide (upper left). Boring data from Shannon and Wilson, Inc. (1964). 

the slide a pseudorotational appearance; however, the causative 

failure and dominant movements 

were horizontal, as verified by the 

perfectly upright attitude of trees 

in the main slide block. Longitudinally, the graben wedge was 

rent by great gaping tension 

cracks. The total relations are 

well illustrated by the aerial view 

(fig. 32) and by the cross sections 

(fig. 33). 

Inasmuch as the slide moved 

outward from a salient, it was unconfined laterally. Accordingly, it 

spread as it moved outward, and 

tension cracks opened in a fanlike 

arrangement at the periphery. 

Some of these tension cracks are 

visible in figure 32. They have 

been plottxl in figure 31. 

A large shallow-rooted pressure 

ridge about 500 feet long at the toe 

of the slide absorbed much of the 

thrust of the slide. At its greatest development the ridge was 

about 15 feet high and 40 to 50 feet 

wide. It wrecked the fuel-storage 

tank at the foot of the bluff (fig. 

32) and overrode overturned trees 

where it thrust forward as much 

as 12 feet (fig. 34). 

Exactly how much the Native 

Hospital slide block was displaced 

laterally has not been determined, 

owing to a lack of good prequake 

horizontal control. Lateral offsets 

in roads and trails that crossed 

the block, however, afford a basis 

for reasonable estimates. These 

estimtutes range from 1'7 feet of 

slippage near the north flank of 
EFFECTS AT ANCHORAGE A53 

34.-Overthrust toe of Native Hospital slide. Road is bulged up and displaced about 12 feet laterally. Note overridden 

trees at left. 

the slide to 25 feet near the center. Furthermore, at least 15 feet 

of slippage can be accounted for 

in the pressure ridge at the toe of 

the slide. Projections to the theoretical slip surface of the slide, 

based on these figures and using 

the graben rule, place the slip surface at a depth of 85 to 95 feet 

or 25 to 35 feet above sea level. 

This altitude is very close to the 

height of the flat on which the 

pressure ridge formed at the foot 

of the slide and to the top of the 

sensitive zone of the Bootlegger 

Cove Clay beneath the bluff. It 

is a probable altitude, therefore, 

for the zone of failure. 'Thus lateral slippage of 17 to 25 feet within the slide block is geometrically 

reasonable. Any appreciably 

smaller slippage would require an 

inordinately deep slip surface to 

compensate for the relatively large 

sectional area of the graben. 

Figure 33 shows cross-sectional 

reconstructions of the Native Hospital slide based on both surface 

and subsurface daka. Although 

subsurface exploration by the 

Corps of Engineers did not disclose the surface of rupture, it did 

clearly define zones of stiff clay 

above and below a zone of weaker 

clay. Mosk of the clay sampled 

had sensitivities below 10, but the 

sensitivity of some of it exceeded 

30. Several thin sand layers may 

have contributed to failure by 

liquefaction. 

Government Hill Slide 

The Government Hill slide 

caused severe dislocations in the 

south-facing bluff on the north 

side of Ship Creek (<fig. 35). Altogether, about 11 acres of land 

was involved, including about 2% 

acres of bottomland below the 

bluff where the slide passed into 

an earthflow and spread out in the 

yards of 'I'he Alaska Railroad. 

The volume of earth involved was 

about 900,000 cubic yards. 

From flank to flank the slide 
A54 ALASKA EARTHQUAKE, MARCH 2 7, 19 64 

35.-Air view of Government Hill slide, Anchorage, Alaska. Graben plainly disoernible. Compare with figure 38. Photograph by Air Photo Tech, Anchorage, Alaska. 

had a width of 1,180 feet. From 

head to toe its greatest length, in 

the direction of slippage, was about 

600 feet. The head of the slide 

regressed back about 400 feet 

behind the prequake bluff line, 

where it intersected the Government Hill Grade School. The 

slide devastated all but one wing 

of the school, destroyed two 

houses, damaged a third, left a 

fourth (since removed) perched 

precariously above a cliff, wrecked 

a shed in the railroad yards at the 

foot of the bluff, and did extensive damage to railroad equipment 

and trackage. 

If any good fortune nccompanied the March 27 earthquake, 

it was its timing; had school been 

in session, the diaster would have 

been unthinkable. The south wing 

of the school dropped as much as 

20 feet vertically into a graben 

after being sheared cleanly in half 

(fig. 3). Electric wall clocks stopped at 5 :36 p.m. The east wing, 

also astride a graben, collapsed 

after being split longitudinally. 

The playground was a mass of 

chaotic blocks and open fissures 

(fig. 36). 

The slide was more complex than 

the Fourth Avenue, L Street, or 

Native Hospital slides. Its complexity was a step further toward 

the total disruption shown by the 

Turnagain Heights slide (fig. 37). 

As shown by the map (fig. 38), a 

complex of arcuate horsts and 

grabens, more or less concentrically disposed, retrogressed head11-ard as the slide pulled away 

from the bluff. Two or three 

partly integrated grabens formed 

side by side along the crown of the 

bluff; these were complicated by 

internal collapses, cracking, and 

slumping along the face of the 

bluff. Two additional grabens 

formed behind the crown on the 

upland surface. The head of the 

slide broke away clean ; back from 

the head there was very little 

cracking and virtually no damage 

to property. 

Each graben was about 100 feet 

across. The two upland grabens, 

however, merged laterally, and at 

their junction the downdropped 

block was 200 feet across. The 

outer grabens were deepest-they 

exceeded 20 feet in depth; the 
BFFECTS AT ANCHORAGE A55 

36.-Wreckage of Government Hill School as viewed from the playground, looking west. Graben in foreground is about 12 feet 

deep. Note undamaged water tower. 

medial graben was 14 to 16 feet 

deep, and the inner graben averaged 12 to 14 feet deep. The intervening horsts glided laterally 

with slight vertical displacement. 

Lateral displacements on the 

slide varied greatly from place to 

place inasmuch as the movement 

of the outermost horst block must 

have equalled the sum of movements of all blocks behind it plus 

its own differential movement. 

Although precise figures for displacement are unavailable, careful 

comparisons of prequake and postquake aerial photographs give 

reasonable approximations. The 

south wing of the elementary 

school shifted laterally 6 to 7 feet 

to the southwest. A house at the 

end of Birch Street, on a horst detached from the main bluff, but 

otherwise little disturbed, moved 

about 35 feet southwestward. On 

the playground south of the school 

building and across a graben from 

the building, a children's slide and 

whirligig moved about 35 feet 

southwestward. South of the 

whirligig across another graben, 

an old concrete blockhouse moved 

about 65 feet. The outermost 

points on the toe of the slide moved 

as much as 150 feet; these points, 

however, moved partly by flowage. 
STA 15 =3 - 

SEA 

120' 

100' 

80' 

60' 

40' 

20' 

LEVEL 

0 01 040 Shear strength Sensitivity 

Shear strength Sensitivity 

(tons per sq ft) (0-40) (tons per sq ft) (0-40) 

Boring 104A projected Boring 107A projected 120 feet southeast 

100 feet southwest 

LEVEL 

37.-Geologic section through Government Hill slide. Boring data from Shannon and Wilson, Inc. (1964). 
38.-Map of Government Hill slide, Anchorage, Alaska. Many small fractures have been omitted. Graben areas indicated by shading. Compare with aerial 

photograph, figure 35. 
A58 ALASKA EARTHQUAKE, MARCH 2 7, 1964 

39.-Homes devastated by Turnagain Heights slide; deep within slide area, upper; 

at main scarp, lolwer. About 75 homes were destroyed. 

Surface inspection of the bluff 

line and subsurface studies by the 

Corps of Engineers indicate that 

the top of the Bootlegger Cove 

Clay is somewhat uneven in the 

Government Hill slide area but 

averages about 70 feet above sea 

level (40 to 55 feet below the original ground surface of the bluff). 

Overlying the clay is outwash sand 

and pebble gravel. 

Shear strength profiles of the 

Bootlegger Core Clay measured by 

Shannon and Wilson, Inc. (1964, 

p. 94) show the characteristic weak 

zone, in which static strength 

ranges from about 0.35 to 0.5 tsf, 

separated by stiffer clay zones 

above and below. Scattered 

throughout the section are lenses 

of sand and silt. In general, the 

strength profiles show a gradual 

decrease in strength to a depth of 

85 to 90 feet (altitude 25 to 30 

feet) followed by a gradual increase in strength down to the 10117- 

est depth tested. The top of the 

weak zone (shear strength less 

than 0.5 tsf) generally lay at an 

altitude of about 40 feet. Most 

sensitivities were relatively low, 

perhaps owing partly to consolidation of the clay after remolding, 

but some were within the range of 

20 to 40. 

Most of the clay contained a percentage of water less than the liquid limit, but some clay-particularly at critical depths near the indicated depth of failure-had natural water contents equal to or 

greater than the liquid limit. 

Thus, the zone of lowest strength 

and highest sensitivity in the clay 

coincided with a zone of critically 

high water-plasticity ratios. 

Failure appears to have occurred somewhere between altitudes of about 20 to 40 feetdepths somewhere between 70 and 

90 feet below the prequake bluff 

line. This depth is very close to 

the top of the weak zone of the 

clay, and is near the altitude (40 

feet) of the flat at the base of the 

bluff in The Alaska Railroad 

yards. It also ooincides closely 

with the minimum depth of failure estimated according to the 

graben rule by using a horizontal 

translation of 35 feet divided into 

a graben sectional area of 2,500 

square feet. 

Several independent factors operating in concert helped precipitate failure. These factors included low shear strength, high 

sensitivity, and water contents exceeding liquid limits, combined at 

a depth where static shear stress 

was critically high, and where 

added stress conditions were introduced by the accelerations of 

the earthquake. An additional 

factor-artificial modification of 
the toe of the bluff by excavations 

at the base of the slope-may have 

contributed to failure by increasing the static shear stress on the 

slope. Aerial photographs ltaken 

in 1962 show plainly that the 

slope had been modified artificially prior to the earthquake. 

Shannon and Wilson, Inc. (1964, 

pl. 13.3), also presented clear evidence that the face of the slope 

had been modified by removal of 

material from the toe. 

Turnagain Heights Slide 

The Turnagain Heights slide 

was the largest, most complex, 

and physiographically most devastating landslide in the Anchorage 

area (figs. 39, 40; pl. 1). It extended west to east along the bluff 

line about 8,600 feet. Its maximum 

head~~ard rekrogre~ssion from the 

bluff was about 1,200 feet ; its average retrogression into the heavily 

populated residential seotion of 

Turnagain Height@, where 75 

homes reportedly were destroyed 

(fig. 39), was about 500 feet. A 

total area of labout 130 acres was 

com~pletely devastated (by displacements that broke the ground into 

countless derangeld blocks, collapsed and tilted at all odd angles. 

The ground surface within the 

slide area ;behind the prequake 

bluff line was lowered an average 

of about 35 feet below khe old prequake level. The volume of earth 

within the slide was about 12% 

million cubic yards. 

Lateral spreading extended the 

slide seaward, as the leading edge 

glicled do~vn the mudflat into Ihik 

Arm beyond the 10x17 tide line. 

Tlle leading edge of the slide extended farther out beyond the old 

bluff line than the head of the slide 

regressed behind ; in most places it 

re:tched inuch farther, even twice 

ns far, before passing below tidewater. Maximum lateral slippage 

exceeded 2,000 feet. Thus, the 

40.-Tree trunk split by tension fracture, Turnagain Heights slide. Many trees 

mere similarly damaged because their roots were firmly embedded in the frozen 

ground. 

landslide, on coming to rest, occupied an area considerably more 

than twice as large as the original 

undisturbed area. 

As seen in plan, the Turnagain 

Heights slide 11-as composite. It 

consisted of tn-o main lobes: a 

West Turnagain lobe and an East 

Turnagain lobe, each in front of 

a separate headwall. Each 'lobe 

probably started as a separate 

landslide, but the two lobes merged 

lat,erally at a northward-projecting salient that was spared of sliding on the new bluff line. This 

salient centered on the mouth of 
A60 ALASKA EARTHQUAKE, MARCH 2 7, 19 64 

41.-Furrowed, sliakensided clay ridge, Turnagain Heights slide. Ridge is about 20 

feet high. Tilted collapsed block at left. Compare with figure 42. 

Hood Creek and extended southward along the Hood Creek ravine. 

For a distance of 150 to 300 feet 

from the creek this shallo~v ravine 

formed an immobile, apparently 

skable, crack-free buttress that projected into the heart of the slide 

and divided the slide into east and 

west counterparts (pl. 1). 

Each lobe removed about 4,300 

feet of bluff line. The West Turnagain lobe, however, retrogressed 

headward much farther and extended farther seaward than the 

East Turfiagain lobe, but the fractured area behind the East Turnagain lobe was much broader and 

more intensely broken than the 

area behind the West Turnagain 

lobe. If the East Turnagain lobe 

had retrogressed to the limit of 

intensive fracturing, it would have 

become a nearly exact counterpart 

of the West Turnagain lobe. 

Apparently the West Turnagain 

lobe had approached a state of 

dynamic stability by the time 

shaking stopped. In other words, 

the lobe probably had retrogressed 

to a point of near equilibrium 

under the dynamic conditions of 

the time; it probably ~~~ould not 

have reached much farther back 

if shaking had continued. The 

ground behind the East Turnagain 

lobe, on the other hand, was left in 

a state of precarious equilibrium 

when shaking ceased; it undoubtedly would have retrogressed 

much farther-possibly as far as 

Northern Lights Boulevard-if 

shaking had continued. 

In addition to the slide proper, 

hundreds of tension fractures (fig. 

40; pl. 1) opened behind the head 

of the slide-as far away as 2,200 

feet from the main scarp of the 

East Turnagain lobe (Engineering 

Geology Evaluation Group, 1964, 

pl. 8b). These fractures were disposed concentrically about the two 

main centers of regression-one 

south of the East Turnagain lobe 

between Fish Creek and Hood 

Creek, and one south of the West 

Turnagain lobe west of Hood 

Creek. Besides causing g r e a t 

structural damage to housing in 

the Turnagain Heights subdivision, these fractures totally disrupted all underground utilities 

and seriously damaged streets and 

curbings. Even more ominous, 

they outlined a potential headward expansion of the landslide 

that was forestalled only by the 

cessation of ground shaking. Continued shaking undoubtedly would 

have involved much more property 

in the landslide. 

The ground behind the East 

Turnagain lobe had in fact begun 

to move, and the displacement increased toward the new bluff line. 

Preliminary studies reported by 

the Engineering Geology Evaluation Group (1964, p. 17) indicated 

that the area along Turnagain 

Parkway between the head of the 

slide and Northern Lights Boulevard was lengthened by more than 

3 feet. Differential movement in 

this distance was taken up by the 

opening of tension cracks. There 

also was subsidence of 6 inches or 

more within a city block of the new 1 

bluff line. Detailed measurements 1 

by Dickinson Oswald and Associates, Anchorage, for the Engineering Department, City of AnI 

chorage (summarized by Shannon 

and Wilson, Inc., 1964, p. 64) indicate that movement occurred 

chiefly before resurveying beganprobably during the strong-motion period of the quake-and that I 

no appreciable movement occurred 1 

during a 3-month period following I 

the quake when detailed measure- 1 

ments were still being made. 

It thus appears that the weak 

zone in the Bootlegger Cove Clay 1 

under the intensely fractured area 

between the slide proper and I 

Northern Lights Boulevard did in- 1 

deed fail, but sufficient shear resistance remained in the block I 

after shaking stopped to prevent 

further sliding. The area at that 

time was buttressed, of course, by 

the passive pressure of the slide debris in front of it. 

At the east margin of the slide, 

the bluff line facing Fish Creek 

held firm despite a sharp local re- 1 
I 

I 42.-Sharp-crested clay ridge, Turnagain Heights slide. Cdlapsed blocks tilted to- 

/ wa~d ridge on both flanks. Note horizontal stratification in ridge. Compare with 

I figure 41. 

lief of 40 feet or more. The slide, position gains support from subin fact, moved nortliwest almost surface data at Fish Creek where a 

diametrically away from Fish boring by the Corps of Engineers 

Creek, leaving behind a somewhat penetrated clay of high strength, 

cracked but otherwise little-dam- low sensitivity, and low wateraged salient or riblike buttress 70 plasticity ratios at the critical 

to 400 feet wide projecting north depths where failure had occurred 1 along Loussac Drive. Conditions nearby. The boring nearest Hood 

at Fish Creek, thus, were compara- Creek (200 feet southeast of the 

ble to those at Hood Creek at the creek) showed high sensitivity and 

far side of the East Turnagain lo\!- shear strength at the critical 

lobe. depth, but it sho~~-ed high strength 

One can but conclude that the and low sensitivity immediately 

shallow valleys of Fish Creek and above. Fish Creek (altitude near 

~ Hood Creek \\-ere instrumental in mean sea level) had eroded its 

1 limiting ground failure in the channel to the depth of the sensiTurnagain Heights slide. Their tive zone, but Hood Creek-a 

function is unclear, but they may smaller stream-had not. But by 

have acted as natural sumps that cutting through the overlying 

partly dematered, and hence sta- clays, Hood Creek must have effecbilized, the adjacent ground in the tively lowered the water table in 

slopes of the ravines and in the the adjacent ground, and in so dobordering uplands some distance ing further stiffened the upper 

back from the ravines. This sup- clays. A drill hole closer to Hood 

Creek might have provided more 

conclusive data. 

Hundreds of sharp-crested clay 

ridges alternating with collapsed 

troughs, and oriented normal to 

the direction of slippage, distinguished the disruption pattern of 

the Turnagain Heights slide from 

all other slides at Anchorage. The 

ridges, however, were exact homologs of the horsts of the Government Hill slide; the troughs were 

exact homologs of the grabens. 

The chief distinction of the Turnagain Heights slide, therefore, 

other than its size, was the utter 

totality of its disruption. Its pattern is well portrayed by the topographic map (pl. 1) and by the 

strip map and section (pl. 2). 

Most of the clay ridges ranged 

in height from about 10 to 15 feet, 

but a few were more than 20 feet 

high. They were as much as 300 

feet long and were spaced 50 to 150 

feet apart. Their steep sides, 

which sloped 60" to TO0, were furrowed and grooved by slippage of 

one surface against another (figs. 

41, 42). On the average, the 

ridges were sharper crested and 

more closely spaced in the West 

Turnagain lobe than in the East 

Turnagain lobe. 

Stratification was greatly disturbed in the collapsed areas between ridges, but it was little distur'bed in the ridges themselves; 

the ridges were displaced virtually without rotation. There was, 

moreover, little vertical displacement as the ridges glided toward 

Knik Arm. Detailed studies 

along the disrupted seaward projection of Turnagain Parkway 

(pl. 2) indicated that clay ridges 

which were displaced as much as 

300 feet laterally were reduced 

only about 12 f& vertically. 

Some of this reduction may have 

been due to attrition at the slip 

surface or to flowage in the sensitized clay below, but most of it 
A62 ALASKA EARTHQUAKE, MARCH 27, 1964 

probably was due to a seaward 

slope on the slip surface itself. 

This slope, then, must have had 

an inc1ina)tion of about 4 percent. 

The complete disruption of the 

ground surface within the Turnagain Heights slide may have been 

due to several factors in combination-including the shallow depth 

to the zone of failure-but the unhindered movement of the slide 

down the wet mudflat toward 

Knik Arm certainly was paramount. In every other translatory slide at Anchorage, slippage 

was resisted by dry or frozen 

ground at the toe and by an 

abrupt flattening of the ground 

slope at the foot of the slide below 

the bluff line. At Turnagain 

Heights, however, the slide broke 

away from the bluff wi'thin the 

intertidal zone and slid out directly onto the sloping tidal muds, 

which themselves were wet and 

sensitive. At the flanks of the 

slide, the tidal flat slopes about 

3", or 5 to 6 percent; before failure it probably had a comparable 

slope in front of the slide also. 

Shear resistance of dry or 

frozen ground in front of a given 

slide must have had a natural buttressing effect that in turn must 

have been a factor in the resistance of the slide to slippage. All 

the translatory slides at Anchorage possessed such natural buttresses except the Turnagain 

Heights slide. The ground at the 

top of the intertidal zone, where 

the Turnagain Heights slide 

sheared to the surface, had previously had little oppodunity to 

desiccate, and the thickness of the 

frozen layer must have been minimal-if indeed, the ground there 

was frozen at all. Reconnaissance along the foot of the \bluff 

several years prior to the earthquake, moreover, disclosed a prevalence of saturation, slumpage, and 

flowage in the clay at the foot of 

the bluff. More or less continuous 

slumpage, abetted by wave and 

tidal action which constantly removed the accumulated debris, 

prevented drying of the naturally 

wet clay and kept the bluff line 

in a precarious state of repose. 

Part of the slip surface of the 

slide was left as a window near the 

west end of the slide, where the 

overlying debris slid free out to 

tidewater (fig. 43). Sliding, however, was not confined to this one 

surface. On the contrary, there is 

every indication that blocks slid 

out one on another at higher levels 

in the same vicinity. In other 

places, failure may have occurred 

mainly at some other level. But 

this surface was plainly an important locus of shearing in this particular part of the landslide. 

Altogether, about a quarter of 

an acre of the slip surface was uncovered. The surface was mantled 

here and there by small pyramidal 

mounds and blobs of clay. Long 

furrows and welts, oriented in the 

direction of slippage (N. 3" W.) 

and extending the length of the exposure, were well preserved 6 

weeks after the earthquake, despite 

desiccation and cracking. 

The surface itself passed below 

highest tide at its seaward margin. It sloped about 15 feet per 

100 feet, on the average, but it was 

convex ; the outer edge was steeper 

than the inner edge. The exposed 

surface was precisely on the projection of the old prequake shoreline, 

so there is no doubt as to where the 

slide sheared off with reference to 

the prequake topography; it must 

have sheared to the ground surface 

at tidewater at the very foot of the 

bluff. 

Mounds of clay left on the slip 

surface, showing evidence of having been overridden themselves, 

mere grooved and slickensided on 

their tops and flanks. Their sides 

sloped steeply down to the slip surface on which they rested, angles 

of 40" to 60°. 

In places the slip surface as 

orerlaiil by blocks of peat and 

forest duff. Frozen at the time of 

the quake, these blocks must have 

been lowered onto the slip surface 

as the intervening incompetent 

clay slid and flowed out from under them. The conclusion seems 

inescapable that the clay overlying 

the slip surface glided seaward 

primarily under the influence of 

gravity ; a window to the slip surface could have been exposed in no 

other way. 

At the extreme east end of the 

slide the slip surface did not break 

through to the ground surface. 

Instead, it died out laterally, as the 

thrust of the sliding mass was 

taken up by a large pressure ridge 

in the tidal silts just below the foot 

of the bluff (fig. 44). This ridge 

cut dramatically at an oblique angle across an old riprap embankment placed along the beach at the 

foot of the bluff-years before 

the earthquake-to retard marine 

erosion. The embankment was 

arched up into an anticline where 

the pressure ridge passed beneath 

it. The ridge was about 700 feet 

long, as much as 50 feet wide, and 

10 to 15 feet high on the landward 

side. On the seaward side it was 

higher and was modified by subsidiary slumping on its oversteepened flank. Just west of the pressure ridge the translatory movement of the landslide was greater, 

and the slide itself was correspondingly more complex. The 

tidal silts failed, and the overriding slide blocks glided far out into 

the Knik Arm. 

Subsurface explorations of the 

Turnagain Heights slide were 

made by the Corps of Engineers 

after an initial investigation was 

started by the Engineering Geology Evaluation Group. Undisturbed samples for field and labo- 
EFFECTS AT ANCHO,RAGE A63 

43.-Slip surface of Turnagain Heights slide exposed near west margin of slide. Furrows and welts still well preserved despite 

desiccation and weathering. Point IToronzof and Knik Arm in distance. 

ratory tests were collected from 

borings at 42 localities within the 

slide and adjacent to it. In some 

places the low strength of the clay 

made it difficult to collect undis- 

, turbed samples; some of this clay 

may have lost strength by remolding. 

Surface and subsurface observations sho~~ed that the Bootlegger 

Cove Clay is mantled by outwash 

sand of some~~hat varied thickness; the sand is about 20 feet thick 

at the east end of the slide and 

tapers nearly to zero at the west 

end. The clay is as much as 100 

feet thick. Shear-strength profiles showed that the clay diminished gradually in strength from 

about 1 tsf at the top of the clay 

to about 0.25 tsf at an altitude of 

15 to 20 feet above sea level; 

it then increasecl gradually in 

strength to about 0.6 tsf at some 

depth (generally about 30 feet) below sea lerel. Talues of minimum 

strength in some borinps \\-ere 

much less than 0.25 tsf, agzzin perhaps because of partial remolding 

of disturbed sensitire clay. 

The depth of lowest strength 

commonly coiilcided with the 

depth of highest sensitivity and 

highest water-plasticity ratios. 

Throughout much of the Turnagain Heights area the clay at lowest shear strength contained water 

in excess of its liquid limit and had 

sensitivities greater than 40. Remolded, this clay had a shear 

strength of about 0.02 tsf (Shannon and IVilson, Inc., 1964, p. 65). 

Thus, the depth of failure probably was 15 to 20 feet above sea 

level, at or near the top of the zone 

of lowest shear strength. This 

altitude also was the height of the 

knick point or slope break at the 
ALASKA EARTHQUAKE, MARCH 2 7, 1964 

base of the bluff before the earthquake-the position at which the 

slide evidently broke to the surface 

and glided seaward down the 

mudflat. 

The mode of failure of the Turnagain Heights slide differs in degree rather than in kind from the 

other translatory slides of the Anchorage area. Some idea of the 

sequence of failure can be had by 

examining different parts of the 

slide where movements had gone 

to different stages of completion 

by the time the earthquake stopped. At the extreme east end of 

the slide near the mouth of Fish 

Creek, for example, the failure 

compared morphologically with 

failure at the Native Hospital 

slide and near the east flank of the 

Fourth Avenue slide. A little 

farther west where the deterioration was somewhat greater, the 

failure was comparable to that in 

the Government Hill slide. 

As stated previously, the slide 

was composite in that it was 

formed by the lateral merger of 

two main ldbes. Within each of 

the main lobes there were subsidiary lobes khat apparently formed 

independently at the bluff line, 

then merged laterally as they retrogressed, 'and finally slid in unison toward Knik Arm. They 

moved different distances, and the 

leading edge of their combined 

mass 'at tidewater therefore had a 

soalloped outline after motion 

ceased. (See map, pl. 1.) In the 

East Turnagain lobe, they slso 

retrogressed unevenly into the 

bluff, making the new bluff line 

very irregular. 

Interference or crowding between subsidiary lobes was accompanied by complex shifting and 

wrenching of blocks. Such movements may have caused lateral 

components of displacement of as 

much as 150 feet in a direction 

parallel Ito the old bluff line-as 

indicated by the postquake positions of objects such as houses 

transported on the slide toward 

Knik Am (Engineering Geology 

Evaluation Group, 1964, pl. 1). 

As the blocks pushed and shoved 

in response to the overall motion 

of the landslide, they &so .wareilurched sharply from side to side 

by the vibratory motion of khe 

earthquake. This lurching was 

mirrored by abrupt deflections in 

furrows and slickensides preserved 

on the sides of clay ridges. 

Some time after the onset of the 

earthquake, the bluff line is visualized as having begun to fail 'along 

a broad front, but mainly from 

one or more centers in each main 

lobe of the slide. Blocks then began to break off headward and ta 

the flanks of each center. Eyewitness accounts indicated that 2 

minutes or more elapsed from the 

start of the quake before the bluff 

began to give way (Shannon and 

Wilson, Inc., 1964, p. 64) and that 

movement continued for some time 

after the earthquake had subsided. 

A particularly lucid and informative report was given by Mr. 

Brooke Marston to Mr. E. R. Bush 

(Grantz, Plafker, and Kachadoorian, 1964, p. 14) : 

I was driving my automobile westward on McCollie Avenue when the 

earthquake accurred. I immediately 

stopped my automobile and waited until 

the quake subsided. It appeared to me 

that the car was rocking from north to 

south. It rocked so violently that I 

nearly became seasick. Wom my car 

I could observe an earth crack alined 

north-south and opening and closing 

from east to west. As soon as the quake 

subsi,ded I proceeded to drive westward 

to the corner of McCollie Avenue and 

Turnagain Parkway. After turning 

right on Turnagain Parkway and driving approximately 180 feet north, I 

realized the bluff was gone north of my 

driveway, which paralleled the bluff in 

an east-west direction. I got out of the 

car, ran northward toward my driveway, and then Faw that the bluff had 

broken back approximately 300 feet 

southward from its original edge. Additional slumping of the bluff caused me 

to return to my car and back southward 

approximately 180 feet to the corner of 

McCollie and Turnagain Parkway. 

After I stopped at this point, the bluff 

continued to slowly slide norbhward as 

I contiqed to back*my auto southward 

on 4 @&Sirway. "Phe bluff 

slowly broke away until the corner of 

Turnagain Parkway and McCollie had 

slumped northward. 

It is my impression that the T'urnagain Bluff area slumped northward in 

segments and that much of the southward receding of the bluff occurred 

after the major earthquake had subsided. 

Prom Mr. Marston's account, it 

is clear that large-scale ground displacements were still in progress 

after the earthquake had stopped. 

After the quake, during the time 

t,llat Mr. Marston drove down 

McCollie Avenue, turned north 

down Turnagain Parkway, got out 

of his car and returned, then 

backed south along Turnagain 

Parkway, stopped, and resumed 

backing-all this after the shaking 

had stopped-the bluff continued 

to regress southward. It regressed 

at least 200 feet, and the elapsed 

time must have been a full minute 

or more. If Mr. Marston had been 

driving 5 miles per 'hour, Eolr example, including backing but not 

counting stops, he would have 

needed 'about 55 seconds to go 400 

feet. He probably drove appreciably fsrther than 400 feet, however, and his stops must have taken 

several seconds each. 

Small-scale slumping continued 

for several days after the quake 

as oversteepened slopes along the 

new bluff line continued to sluff 

away and frozen blocks of sand 

and forest duff began to thaw. 

One house, left precariously balanced, but not severely damaged 

on the rim of the bluff at Chilligan 

Drive, toppled and collapsed several days later. So far as is 
0 50 100 150 FEET 

L888ll 

APPROXIMATE SCALE 

I I 

44.-Sketch section through eastern part of Turnagain Heights slide. Note pressure ridge, upright blocks at center 

and to left of pressure ridge, and tilted collapsed blocks between. 

known, aftershocks did not cause 

any additional sliding. 

Failure at Turnagain Heights 

probably occurred near the top of 

the lowest-strength zone of the 

Bootlegger Cove Clay, at an altitude of 15 to 20 feet above sea 

level. Inasmuch as the top of this 

zone was a subhorizontal surface, 

the failure itself must have been 

along a subhorizontal surface also, 

and the initial movements of the 

slide must have been translatory. 

Because the clay contained water 

in excess of its liquid limit, because the strength of the clay 

under pulsating or vibratory stress 

was appreciably less than under 

static stress, and because the zone 

of lowest strength coincided with 

the zone of highest sensitivity, the 

face and crown of the bluff werein effect-afloat on a liquefied 

layer of viscous clay. The bluff 

then began to glide slowly seaward under the influence of 

gravity, leaving a gaping crack in 

its wake. The presence of open 

cracks-denoting release of tension-is significant ; nearly all eyewitness reports allude to them. 

Earth materials strained under 

horizontally directed tension commonly have two sets of tension 

fractures: one set antithetical to 

the other such that alternate fractures dip toward and away from 

one another and both sets are oriented normal to the direction of 

maximum tension. As the slide began to spread, countless tension 

fractures disrupted its surface and 

the surface of the ground behind 

the slide ; after movement stopped, 

incipient grabens were preserved 

in the subdivision behind the slide. 

A 1 o n g antithetical fractures 

dipping south, the unsupported 

hanging wall generally collapsed 

toward the north; along fractures 

dipping north, the hanging wall 

collapsed toward the south. At a 

given clay ridge bounded by 

opposed fractures dipping away 

from the ridge, adjacent collapsed 

blocks commonly were tilted toward the ridge on both flanks 

(figs. 41, 42). Farther from the 

ridge in the bottom of the adjoining trough or graben, collapsed 

blocks were tilted into helterskelter attitudes. 

As each new block pulled away 

from the bluff, the new bluff line 

was left unsupported on the seaward side. Tension fractures reduced support on the landward 

side. Blocks were pulled away 

successively by gravity as long as 

the shear resistance at the slip surface was exceeded by the force of 

gravity plus the accelerations of 

the earthquake. When the earthquake stopped, the force of gravity 

alone was sufficient to cause largescale failure for some time after- 

\\-ard. And in the hanging wall of 

each tension fracture, subordinate 

blocks collapsed and toppled under their own weight-the entire 

mass at the same time gliding 

slowly toward Knik Arm. 

After the earthquake, the outermost slide block of the original 

bluff line was preserved to view 

only at the extreme east end of 

the slide (fig. 44) where the thrust 

of the toe was countered by a pressure ridge. Elsewhere along the 

front of the slide, where movement 

was much greater, the toe of the 

slide and the old bluff line passed 

beneath the waves of Knik Arm. 

Only at the east end of the slide, 

therefore, where the movement did 

not go to completion, is it possible 

to visualize what happened at the 

outset when the bluff first began to 

fail. Rotational movement at the 

east end of the slide is ruled out; 

stratification in the Bootlegger 

Cove Clay was undisturbed despite 

lateral shifting of several feet, and 

trees on the slide block remained 

perfectIy upright. Rotational effects came into play behind the 

block, however, where the overhanging trailing edge of the block, 

lacking support, tilted backward 

and collapsed. 

Some idea of the complexity of 

the disruption is presented in 

plates 1 and 2 and in a restored 

section through the slide prepared 

for the Corps of Engineers by Seed 
A66 ALASKA EARTHQUAKE, MARCH 27, 1964 

(in Shannon and Wilson, Inc., 

1964, pl. 10.8). Seed's restoration 

is in general agreement with figure 

43 and with the steps previously 

outlined, although it emphasizes 

the part played by rotation in the 

process and minimizes the effects 

of translatory motion. Seed's restol-ation also contains minor geometric inconsistencies. Contrary 

to Seed's view, translatory mot.ion 

under gravity is here envisaged as 

the primary operative mechanism 

of landsliding, not only at Turnagain Heights but at the other major slides in Anchorage as well. 

Rotation, as well as flowage, must 

have occurred in some degree in all 

the slides, but rotation is viewed 

as a subordinate process not germane to the failure of the ground, 

even though it certainly was significant in the disruption of the 

ground surf ace. 

LANDSLIDING PRIOR TO THE MARCH 27 EARTHQUAKE 

Geologic evidence indicates that 

landslides similar to those set off 

by the March 27 earthquake have 

occurred previously in the Anchorage area. Most of these slides predated the settlement of Anchorage, and it is not known, therefore, 

whether or not most of them were 

triggered by earthquakes; the 

morphology of some, by analogy 

with the March 27 slides, suggests 

that earthquakes have had a part. 

Some inferences as to timing suggest the same. The earthquake of 

October 3, 1954, clearly triggered 

slides along The Alaska Railroad 

near Potter Hill. 

Evidence of old landslides in 

certain areas of Anchorage has 

been cited elsewhere in this report 

(p. A31, A49). The evidence is 

here reitera4ted, together with evidence of sliding elmhere. Miller 

and Dobrovolny (1959) recognized 

many areas of past landsliding, 

showing them on their map (pl. 1) 

as "areas covered by landslides, 

slumps, or flows," with the prognosis that "shocks, such as those 

associated with earthquakes, will 

start moving material that under 

most conditions is stable" (p. 104). 

Old landslides, like recent ones, 

were concentrated along bluff lines 

where topographic relief caused 

high static-shearing stress on the 

underlying soil. Most old slides 

have the form of recessed alcoves 

with uneven terracelike floors. 

Small slides may have the form of 

steplike breaks on the sides of the 

bluffs. Some slumps have left 

lobate accumulations of earth at 

the foot of the bluffs. The fact 

that an area has slid previously 

apparently is no basis for predicting that it will or will not slide 

again. Many former landslides 

were stable during the March 27 

earthquake, but in some places new 

slides were superimposed directly 

on old ones. 

Compelling evidence of previous 

translatory sliding was found at 

the site of the Native Hospital 

slide, where a well-preserved graben was truncated by the slide of 

March 27. The old slide block 

and its graben are shown well in 

figure 32. Birch trees growing on 

the scarp of the old graben average 

about 7 inches in trunk diameter 

at breast height. Trees of that 

size on well-drained ground in the 

Anchorage area average about 60 

years in age (Reed and Harms, 

1956, p. 241). Five years or more 

may have been required after sliding to establish forest growth on 

the raw gravel. About 65 years, 

therefore, is the probable minimum age of the slide, an age which 

dates to about the turn of the century. Many earthquakes, some of 

them severe, occurred at about that 

time in southern Alaska (Davis 

and Echols, 1962), and one of them 

might have triggered landslides at 

Anchorage. The great Yakutat 

earthquake of 1899 was felt in 

much of southern Alaska, including points more distant that Anchorage (Tarr and Martin, 1912, 

p. 68 and pl. 33), but whether the 

quake's intensity was sufficient to 

trigger landslides as far am-ay as 

Anchorage is uncertain. 

Remnants of old slides are abundant elsewhere along the bluffs of 

Ship Creek. Between the Native 

Hospital slide area and the Fourth 

Avenue slide area, the Alaska 

State Highway Department facilities are located in an old slide area 

that was partly reactivated on 

March 27. The alwvelike area 

centered at the city parking lot 

north of Fourth Avenue, between 

C and E Streets, probably lalso is 

the scar of an old landslide (Shannon and Wilson, Inc., 1964, p. 39; 

R. M. Waller, written commnn., 

1965). The area coincides almost 

exactly with the Fourth Avenue 

slide of March 27, except that the 

Fourth Avenue slide retrogressed 

farther into the bluff. The salient 

west of this slide partly bounded 

by Christensen Drive and Second 

,4venue appears to be a lowered 

slump block. 

On the north side of Ship Creek, 

the recess just west of the destroyed Government Hill School 

may be an old slide scar. Points 

farther west along the bluff and 

north around the bend above the 

Port of Anchorage have many of 

the topographic markings of landslides, including alcoves, step ter- 
EIFFECTS AT ANCHORAGE 

races, and grabenlike depressions. 

The bluff at Cairn Point below the 

Elmendorf Moraine has a long 

history of minor slumping. Evidence of prior slumping along 

Bluff Road east of Government 

Hill School l~as been noted previously. 

Along the bluff above Knik Arm 

between L Street and 0 Street, 

scallop-shaped recesses and terracelike benches below the crown 

of the bluff probably are old slide 

blocks. A remarkable channellike 

trench thst trends dilagonally 

southwest from the vicinity of R 

Street and Tenth Avenue toward 

S Street and Eleventh Avenue 

probably is a remnant of an old 

graben. Trees in this trench are 

comparable in size to those in the 

old graben near the Alaska Native 

Hospital. 

Farther southwest nmr the 

mouth of Chester Creek, the bench 

along Bootlegger Cove Drive 

Alaskan Construction Consultants Committee [1964], Reconstruction and 

development survey of earthquake 

damage in Alaska: Prepared for 

and published by Federal Reconstruction and Development Planning Commiseion for Alaska ; Honorable Clinton P. Anderson, U.S. 

Senator, Chairman, 98 p. 

Berg, G. V., and Stratta, J. L., 1964, 

Anchorage and the Alia'ska earthquake of March 27,1964 : New Pork, 

Am. Iron and Steel Inst., 83 p. 

Bjermm, Lauri'bs, 1954, Geotechnical 

properties of Norwegian marine 

clays : Geotechnique, v. 4, no. 2, p. 

49-89. 

1995, Stability of natural slopes 

in quick clay: Geotechnique, v. 5, 

no. 1, p. 101-119. 

Cams, 5. R., 1916, The Turnagain-Knik 

region: U.S. Geol. Survey Bull. 

642-E, p. 147-194. 

1940, Geology of The Alaska 

Railroad region : U.S. Geol. Survey 

Bull. 907, 201 p. 

probably is an old slide block, and 

due east from there the broad recess centered near Inlet View 

School probably is an old slide 

area also (fig. 27). This feature 

is very subdued and probably is 

very old. 

The bluff line along the south 

side of Chester Creek from the 

mouth of the creek discontinuously 

as far east as Rogers Park shows 

evidence of past slumping. Terracelike features lacking continuity along the valley margin, 

especially those deeply recessed 

into alcovelike niches, or those having irregular floors-particularly 

back-sloping floors, probably are 

slump blocks. On March 27 a 

small slump occurred in the bluff 

just north of West High School. 

Forest Park Golf Course between 

the mouths of Chester and Fish 

Creeks appears to be situated in 

an area of old landslides. 

REFERENCES 

Casagrande, Arthur, 1947, Classification and identification of soils : Am. 

Soc. Civil Engineers Prw., V. 73, 

no. 6, pt. 1, p. 783-810. 

Casagrande, Arthur, and Fadum, R. E., 

1944, Application of soil mechanics 

in designing building foundations : 

Am. Soc. Civil Engineers Trans., v. 

109, Paper 2213, p. 383-490. 

Cederstrom, D. J., Trainer, F. W., and 

Waller, R. M., 1964, Geology and 

ground-water resources of the Anchorage area, Alaska: U.S. Geol. 

Survey-Water Supply Paper 1773, 

108 p. 

Crandell, D. R., 1952, Landslides and 

rapid-flowage phenomena near 

Pierre, South Dakota; Econ. Geology, v. 47, no. 5, p. 548-568. 

1958, Geology of the Pierre area, 

South Dakota: U.S. Geol. Survey 

Prof. Paper 307,83 p. 

Davis, T. N., and Echols, Carol, 1962, 

A table of Alaskan earthquakes, 

1788-1961 : Alaska Univ. Geophys. 

West from Fish Creek to Point 

Woronzolf the bluff line has liad 

a long history of slumping. There 

is no indication of previous sliding 

comparable to the disastrous 

Turnagain Heights slide, but 

small-scale sluffing away and localized slumping were continuing 

problems; the long-range effect 

\\-as a slow but relentless sapping 

away of the bluff line. 

The long bluff line south of Anchorage facing T'urnagain Arm 

showed little evidence of landsliding prior to the March 27 earthquake except at Potter Hill ,and 

Point Campbell. Slumping at 

Potter Hill has been a recurrent 

problem, only in part caused by 

earthquakes. At Point Campbell, 

intermittent debris slides and sand 

runs have been caused by ordinary 

wave and current erosion at the 

foot of the bluff-proceses unrelated b earthquakes. 

Inst. Geophys. Research Rept. 8 

[UAG-R131],43 p. 

Davis, S. T., and Juan Karzulovic K., 

1963, Landslides at Lago Rifiihue, 

Chile : Seismol. Soc. America Bull., 

v. 53, no. 6, p. 1403-1414. 

Eide, Ove, and Bjerrum, L., 1955, The 

slide at Bekkelaget : Norges Geotek. 

Inst. Pub. 10; Geotechnique, v. 5, 

no. 1, p. 88-100. 

Engineering Geology Evaluation Group, 

1964, Geologlc report-27 March 

1964 earthquake in Greater Anchorage area : Prepared for and published by Alaska State Housing Authority and the City o~f Anchorage, 

Anchorage, Ala~ka, 34, p., 12 figs., 

17 pls. 

Federal Reconstruction and Develop 

ment Planning Commission for 

Alaska, 1964, Response to disaster, 

Alaskan earthquake, March 27, 

1964 : Washington, U.S. Govt. Printing Office, & p. 

Fuller, M. L., 1912, The New Madrid 

earthquake : U.S. Geol. Survey Bull. 

494,119 p. 
A68 ALASKA EARTHQUAKE, MARCH 27, 1964 

Goddard, E. N., chm., and others, 1948, 

R o c k-color chart : Washington, 

Natl. Research Council (repub. by 

Geol. Soc. America, 1951), 6 p. 

Grantz, Arthur, Plafker, George, and 

Kachadoordian, Reuben, 1964, Alas 

ka's Good Friday earthquake. 

March 27, 1964, a preliminary geologic evaluation : U.S. Geol. Survey 

Circ. 491,35 p. 

Karlstrom, T. N. V., 1957, Tentative correlatibn of Alaskan glacial sequences, 1956: Science, v. 125, no. 3237, 

p. 73-74. 

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. 

Lambe, T. W., 1958, The structure of 

compacted clay : Am. Soc. Civil Engineers Proc., v. 84, SM2 Paper 

1654, 34 p. ; reprinted, 1960, im Am. 

Soc. Civil Engineers Trans., v. 125, 

pt. 1, p. 682-706. 

McMinn, J. H., 1964, The verdict of 

Anchorage-good structural design 

survived : Eng. News-Record, v. 172, 

no. 15, p. 23-25. 

Meade, R. H., 1964, Removal of water 

and rearrangement of particles 

during compaction of clayey sediments-review : U.S. Geol. Survey 

Prof. Paper 497-B, p. B1-B23. 

Miller, R. D., and Dobrovolny, Ernest, 

1959, Surficial geology of Anchorage 

and vicinity, Alaska : U.S. Geol. 

Survey Bull. 1093, 128 p. 

Mitchell, J. K., 1956, The fabric of 

natural clays and its relation to 

engineering properties : Highway 

Research Board Proc., v. 35, p. 

693-713. 

National Board of Fire Underwriters 

and Pacific Fire Rating Bureau, 

1964, The Alaska earthquake, 

March 27, 1964: San Francisco, 

Calif., 35 p. 

Odenstad, Sten, 1951, The landslide at 

Skiittorp on the Lidan river, February 2, 1946: [Royal] Swedish 

Geotech. Inst. Proc., no. 4, 40 p. 

Reed, J. C., Jr., and Harms, J. C., 1956. 

Rates of tree growth and forest 

succession in the AnchorageMatanuska Valley area, Alaska : 

Arctic, v. 9, no. 4, p. 239-248. 

Rosenqvist, I. T., 1960, Marine clays and 

quick clay slides in south and central Norway : Internat. Geol. Cong., 

21st, Oslo, Norway, 1960, Guide to 

Excursion C13, 27 p. 

1962, The influence of physicochemical factors upon the mechanical properties of clays, in Swineford, Ada, ed., Clays and clay minerals: Natl. Conf. on Clays and 

Clay Minerals, Qth, Lafayette, Ind., 

, 11960, p. 12-27. 

,/~chmidt, Ruth A. M., 1963, Pleistocene 

marine microfauna in the Bootlegger Core Clay, Anchorage, Alaska : 

Science, v. 141, no. 3578, p. 350-351. 

1964, Geology in a hurry: Geotimes, v. 9, no. 3, p 13-15. 

Shannon and Wilson, Inc., 1964, Report 

on Anchorage area soil studies, 

Alaska, to U.S. Army Engineer District, Anchorage, Alaska : Seattle, 

Wash., 109 p., app. A-K, pls., illus. 

Steinbrugge, K. V., i964, Engineering 

seismology aspects, in Prince \Villiam Sound, Alaskan earthquakes, 

March-April 1964 : U.S. Coast and 

Geod. Surrey, Seismology Div., 

Prelim. Rept., p. 68-72. 

Stokes, W. L., and Varnes, D. J., 1955, 

Glossary of selected geologic terms 

with special reference to their use 

in engineering : Colorado Sci. Soc. 

Proc., v. 16, 165 p. 

Tarr, R. S., and Martin, Lawrence, 1912, 

The earthquakes at Yakutat Bay, 

Alaska, in September 1899: U.S. 

Geol. Survey Prof. Paper 69, 135 p. 

Terzaghi, Karl, 1950, Mechanism of 

landslides, in Application of geology to engineering practice (Berkey 

volume) : New York, Geol. Soc. 

America, p. 83-123. 

Terzaghi, Karl, and Peck, R. B., 1948, 

Soil mechanics in engineering practice: New York, John Wiley & Sons, 

Inc., 566 p. 

Trainer, F. W., and Waller, R. M., 1965, 

Subsurface stratigraphy of drift at 

Anchorage, Alaska : U.S. Geol. Survey Prof. Paper 525-C, 1965. 

U.S. Bureau of Reclamation, 1960, 

Earth manual-A guide to the use 

of mils as foundations and as construction materials for hydraulic 

structure, 1st ed. : U.S. Bur. of Reclamation, Denver, Colo., 751 p. 

17.5. Geological Survey, 1962, Anchorage and vicinity, Alaska : U.S. Geol. 

Survey topographic map series, 

scale 1 : 24,000. 

Varnes, D. J., 1958, Landslide types and 

processes, in Eekel, E. B., ed., Landslides and engineering practice : 

Natl. Research Council, Highway 

Research Board Spec. Rept. 29, p. 

20-47. 

Waller, R. M., Thomas, H. E., and Vorhis, R. C., 1965, Effects of the Good 

Friday earthquake on water supplies: Am. Water Works Assoc. 

Jour., v. 57, no. 2, p. 123-131. 

White, J. E., 1965, Seismic waves-radiation, transmission, and attenuation : New York, McGraw Hill Rook 

Co., 302 p. 

U.S. GOVERNMENT PRINTING OFFICE : 1965 -783-132