A Study of the Source Mechanism of the Alaska Earthquake and Tsunami of March 27, 1964 Part 1. Water Waves! GEORGE PARARAS-CARAYANNIS
ABSTRACT: The geologic history and the general geomorphology of the area affected by the March 27, 1964 Alaska earthquake are given. The tsunami-generat ing area is determ ined and the extent of crustal displacement and the limits of the areas of subsidence and uplift, as revealed by geologic evidence, are discussed. The dimensions of this tsunami-generating area, its volume of crustal displacement, and the energy associated with the tsunami are calculated. Wave activity within and outside the generating area and the possible generating mechanisms for the tsunami are discussed. A wave refraction diagram of the Alaska tsunami for the north Pacific Ocean area is presented in Figure 6.
THE ALEUTIAN ISLAND ARC and the Aleutian The nature of the termination of the eastern Trench extend for 2800 km from Kamchatka segment of the Aleutian Trench is obscured to south-central Alaska along remarkably smooth by thick sediments washed in from the conti curves which are convex toward the south (Fig. nent al shelf against which it abuts offshore 1). The Arc forms the Alaska Peninsula and, from Cape Suckling. The sediments are of geo according to Wilson (1954), intersects, north synclinal-dimensions in the sedimentary arc of Cook Inlet, a second tectonic arc that ex on Kodiak Island (Menard and Dietz, 1951) tends northward from the vicinity of the and as shown by drilling on the Kenai Penin Wrangell Mountains. However, Plafker (1965) sula. Woollard et al. (1960) show there is regards this second segment as a continuation geophysical evidence for at least 7 km of sedi of the Aleutian Arc. Where the trench im ments in Cook Inlet, a graben separating the pinges on Alaska it loses its identity, although primary arc from the offshore sedimentary arc. an offshore range of seamounts suggests it may Sediment is about 2 km thick off Kodiak Island once have extended around to the south to along the Aleutian Trench, thinning out to parallel the continental slope, as postulated by about 0.7 km south of Unimak Island in the Menard and Dietz (1951). Concavity in the deep water area, according to seismic measure former shape of the trench on its eastern seg ments by Shor (1962). ment is also suggested by the sedimentary arc defined by Wilson (1954), which embraces THE GENERATING AREA OF THE ALASKA Kodiak Island and the Kenai Peninsula. As TSUNAMI shown by Wilson, such concavity is to be ex pected where two arcs meet at an acute angle, According to Van Dorn (1964) , the tectonic as is well exemplified where the Aleutian and dislocations associated with the Alaska earth Kuril-Kamchatka arcs intersect. It is also quite quake of March 27, 1964 ranged over a dis possible that large horizontal movements of tance of 800 km, from the upper portion of crustal blocks have helped to change the shape Prince William Sound to southwest of the of the Trench and Arc on their eastern seg Trinity Islands . The dislocations follow a di ments. However, no such evidence was found pole pattern of positive and negative displace in a field study following the Good Friday ments on either side of a zero-line which, earthquake (Berg et al., in preparation) . intersecting the east coast of Kodiak Island, continues northeast to the western side of Prince i Hawaii Institute of Geophysics Contribution No . 184. Manuscript received June 22, 1966. William Sound. There, changing direction, it 301 302 PACIFIC SCIENCE, Vol. XXI, July 1967
154" ALASKA RANGE
60"
58"
ALAS KA
100 ~ 0 50 . SGAl.[ ~ 11101
' .'.:
154 " 148"
FIG. 1. Generating area of the Alaska tsunami. Crosshatched area indic ates (-) area of subsidence and (+) area of upl ift . Heavy dashed lines indicate the backward-refracted wave fronts . Solid line marked by a zero is the axis of rotation (n o elevation change). Other solid lines indicate tectonic axes.
runs east along the upper part of the sound. tonic uplift closely corresponds to a major The line roughly parallels the Aleutian Trench crustal fault defined by crustal seismic mea axis and separates the Kodiak geosyncline from surements conducted by the Department of the shelf geanticline. Terrestrial Magnetism of the Carnegie Insti The areas north and west of this line have tution of Washington (Woollard et aI., 1960). undergone negative elevation changes, whereas In view of the shallowness of the earthquake the east and south underwent positive changes. (20 km), it was concluded that the crustal An extensive pattern of positive surface dis dislocations occurred alongside a zone of tilt locations under the sea is suspected to lie east ing or a surface rupture (Grantz et al., 1964) , of the island of Kodiak and along the conti but a survey of the area failed to identify such nental shelf bordering the Gulf of Alaska. a feature. The focal depth corresponds, how The extent of these dislocations still needs to ever, to the base of the granitic layer defined be confirmed by detailed bathymetric surveys by Woollard's analysis of the crustal measure of the area, although large positive displace ments made by the Carnegie Institution. ments have been observed as far south as The total area of tectonic displacements asso Middleton Island and southwest to Sitkinak ciated with the Alaska earthquake of March Island. Wave refraction studies, described 27, 1964 is estimated to be approximately here, also strongly indicated that the tsunami 215,000 krn-. This is the largest area known generating area was mainly in the belt of uplift to be associated with a single earthqu ake within and included a large segment of the conti historic time. nental shelf and slope. The magnitude of the Alaska earthquake The zone between the known areas of tee- was estimated to be from 8.4 to 8.75, which Alaska Earthquake and Tsunami, I-PARARAS-CARAYANNIS 303 is greater than the 1906 San Francisco earth Such a method of preparing refracti on diagrams quake ( 8.3), and equal to or greater than the has shown good results, especially if carried out 1960 Chile earthquake (8.4). The epicenter on large-scale charts with detailed bathymetry of the earthquake was at 61.05 °N, 147.7°W (Johnson, O'Brien, and Isaacs, 1948) . (USCGS, 1964) , near the east shore of Una In constructi ng the refraction diagrams for kwik Inlet in northern Prince William Sound . the Alaska tsunami, the marigrams of different Geological investigations have defined the tide gauge stations around the Pacific were con land areas affected by the earthquake. To the sulted and the total travel time of the first wave east, the zone of deformation appears to die out at each station was determined. Then refractio n between the Bering Glacier and Cape Yakataga . diagrams were constructed toward the earth The northwestern limit of tectonic changes quake area from each tide gauge station in extends at least to the west side of Shelikof lengths of time equal to the calculated travel Strait and Cook Inlet (Plafker , 1965) . The time for that station. It was assumed that the north inland limit is known only along the last wave front in each refraction diagram would highway connecting Valdez and Fairbanks; it correspond to a point on the boundary of the appears to extend in a northeasterly direction generating area, and if enough refracted wave to the vicinity of the Wrangell Mountains, and fronts from different stations were plotted, an quite possibly into the Alaska Range. envelope defining the tsunami-generating area The area of uplift covers about 105,000 km could be drawn. and extend s from southern Kodiak Island north W ave fronts were refracted from Yakatat, east to Prince William Sound . It includes the Cape Yakataga, Seward, Uzinki, Kodiak, Old southern and eastern parts of Prince William Harbor, Unalaska, Adak , Attu , and Honolulu. Sound , the coastal area as far east as the Bering The last front of each of the refracted waves is Glacier, and the continental shelf and part of shown by a heavy dashed line in Figure 1. The the slope to a depth contour of approximately seaward boundary of the generating area is near 200 m. The maximum uplift on land was 10 m the 200-m depth contour which defines the edge at the southwest end of Montague Island, but of the continental shelf. Maximum displacement is suspected to have been considerably more off of the ocean floor occurred along the continental shore. Uplift also occurred along the extreme shelf, from an area south east of Kodiak Island, southeastern coasts of Kodiak Island and Sitka to an area close to Cape St. Elias south of the lidak Island, and part or all of Sitkinak Island. island of Kayak (Fig. 1) . Geologic evidence, The maximum measured uplift of Sitkalidak however, has shown positive land displacements Island was 0.4 m. The estimated uplift of Sit as far north as Cape Suckling and as far east kinak Island was from 0.35 to 0.65 m and pos as the Bering Glacier. It is quite prob able, there sibly as much as 1.5 m ( Plafker, 1965). fore, that the tsunami-generating area extended The area that subsided included the northern farther to the northeast, although waves gener and western parts of Prince William Sound, ated in such shallow water would reach tide the western segment of the Chugach Mountains, gauges much later and their origin would not portions of the lowlands north of them, most be identifiable. of the Ken ai Peninsula, and almost all of the Unfortun ately, this same wave refraction tech Kodiak Island gro up. This area of subsidence nique could not be used to define the northern covers approximately 110,000 krn-, and is and western boundaries of the main tsunami 800 km long and 150 km wide. Plafker (1965) generating area, because conditions in Prince estimates that the volume of crust that has been William Sound and elsewhere along the coast depressed below its pre-earthquake level is about of Alaska were further complicated by local 115 krn", tsunamis, oscillations, and surge. In addition, The seaward limits of the earthquake and the no tide gauge stations were operating in the tsunami-generating area were determined by area, and personal accounts were conflicting as means of a series of refraction diagrams based to arrival times of the different waves. on Snell's Law of Refraction using the velocity The northward limit is assumed to be re equation for shallow water waves, C = Vgd. stricted by the land boundaries, and the western 304 PACIFIC SCIENCE, Vol. XXI, July 1967 limit to extend to the west side of Shelikof of an hour or more:' Th eir energy radiation was Strait and Cook Inlet. preferentially directed toward the southeast and In estimating the travel time of the tsunami, this is why more damage was done to the N orth corrections were made for the delay at the is American coast than anywhere else east or south land of Kodiak in the arrival of the ground of the generating area. This preferential direc shocks from Prince William Sound. These cor tivity of energy radiation can be attributed to rections ranged from 1 minute to 6 minutes and the orientation of the tectonic displacements were based on the fact that the Navy W eather along the continental shelf of the Gulf of Central on the island of Kodiak listed the time Alaska, and the long period of the waves can of the principal shock in Prince W illiam Sound be related to the long seiche period of the as 6 minutes later than the time listed by the shallow shelf. U. S. Coast and Geodetic Survey. This would According to Japanese seismologists (Iida, imply that the wave front generated on the 1958), the generating area of a tsunami roughly northeast side of the disturbance area had a 6 corresponds to the distribution of the major minute head start on the wave front generated aftershocks. This appears to be indeed the case southeast of Kodiak. in the Gulf of Alaska. The tsunami-generating area covers an area There were 52 aftershocks of the Alaska 700 km long by 150 km wide, a total of about earthquake. The largest had a magnitude of 6.7. 105,000 krn-, The volume of the uplifted crust The aftershocks occurred in an area from about along the continental shelf is about 96 krn". The 15 km north of Vald ez to about 55 km south of energy associated with the tsunami has been Trinity Islands, and were heavily concentrated estimated by Van Dorn ( 1964) to be of the on the northeast and the southwest of the up order of 2.3 X 1021 ergs. This estimate is based lifted region (USCGS, 1964), which also was on the source dimensions of an area 240 nau the main tsunami-generating area. tical miles by 100 nautical miles and an uplift The vast area of tectonic movements indicates of 1.8 m (6 ft) at the northeastern end of this that wave crests were generated along one or area and zero at the southwestern end. This more line sources from the region of maximum estimate, however, is considered low because the upli ft. Thus, the shores of the Kenai Penin sula generating area had dimensions that were larger were struck within 20 minutes after the start of than those estimated by Van Dorn. the earthquake, and those of Kodiak Island , Using our source dimensions, and assuming within 34 minutes. that the total energy was equal to the potent ial Unfortun ately, the violence of the earthquake energy of the uplifted volume of water, the left south-cent ral Alaska without a tide gauge total energy for the tsunami in the Gu lf of in operation. The only reliable record from the Alaska was calculated as follows: generating area is the one that was obtained by personnel of the U. S. N avy Fleet W eather 1 2 Et = - pgh A Station at Kodiak; it is shown in Figure 2. This 6 record has been corrected for the 1.7-m (5 .6-ft) 1 = - (1.03) ( .980) (1 03 ) (104 ) ( 1.832 ) (1.5 submergence of the area. 6 Outside the immediate generating area, the 7 7 21 X 10 ) (7 X 10 ) = 5.88 X 10 ergs record of Cape Yakataga, as constructed from where the personal account of C. R. Bilderback, a resi dent of the area, is the next most reliable record. E, = E" = total energy p = 1.03 g/cm3 = density This record is the only one obtained outside g = 980 cm/sec2 the generating area that shows an initial drop h = height of displacement = 1.83 m in the water level (Berg et aI., in preparation) . A = area Withdrawal of the water immediately following 1 erg = g cm2 sec- 2 the earthquake has been reported from Kayak, The waves generated in the Gulf of Alaska Middleton, and Hinchinbrook islands, as well were of an unusually long period, on the order as from Rocky Bay and N uka Bay, at the end Alaska Earthquake and Tsunami, I-PARARAS- CARAYANNIS 305
7 )0 6 9 m~ ! I 5 8 1:la • r. 1:r. 1I i 4 0 :I: a:: 7 " II i: ~11 it, II ITI w • II II 1:1:11 , I I Gi N II II r 'I ~ 1~ :1i " Il n 11 3 :I: IJ.. 6 II 'I II 'I ii 1.,lk,'h:·.'! ,1 : -t IJ.. II 'II I..' :l> ,II 'I 'I :: ': ::"0).. . : m I 'I II' ,I II ~ 'J I T" '" I," r·J , ' 2 ~ \ I ~ ', '1 I "'I', , " I ~ I 1 en 5 II I I ,I ~ I .. ''1,:: . ,',': ' '::, :,"'.' , ~ len I 'I I II ,.:[1\,,, I ,' II: ': :,11' III j - ,; I S:::ITI I 'II' 0 " "1111 I" I 11111 ' 1 1 I ,. . ' Wa:: III " .' 111I'll I I ~ I III II ' II I " I" lTI I : I~ " I il Ow ",q I::: I" I If1 : ' 11 : :'1 I II: ' 0, -t o -I- 4 f I I 1 I, . II' I' 1 11 11, ,I I 1'1, " I- '1 . I lTIen w i -. I I I .,.; ::: I I , '1':: I:: I :: :: nI : : : : I:: -. . :u-t w;:;: --- : - ' ;-; '~I -'-111--"'- 1:1:-1, ,-:-,11, 11 11 ll:l--- "~ " 0 en : I I I :' I I 1/ I I ~ I I.:' I I • I, I ' I' o 3 ~ c e> . I I :; :' I'~ I"~ : II, :; ' : m / 1 II I I 'II 1 1'1 ,,:. :l> : ~ : r I : I ~ : : ~ - ) FIG. 2.D iagram of wave actrvity at Women's Bay, Kodiak Island . (From visual observations made at Marginal Pier, N yman Peninsula. ) of the Kenai Peninsula, but these islands are TSUNA MI GE NERATED IN PRINCE WILLIAM inside the generating area. SOUND Yakatat, a coastal town 170 km southeast of Cape Yakataga, had a tide gauge in operation, The shallow continental shelf and the islands and the marigram shows that a positive wave bordering the southern side of Prince William arrived first (Fig. 3) . Sound , as well as the pattern of crustal displace It is quite possible, therefore, that the first ments, confined the waves generated in this area waves to arrive at Cape Yakataga had a differ to the Sound itself; very little energy escaped ent origin from that of the first waves to arrive this closed region. Most of the energy was ex at Yakatat. It could very well be that the Cape pend ed in the narrow, deep fjords of the Sound, Yakataga waves traveled over the shallow por creating catastroph ic waves and setting up reso tion of the shelf, whereas the Yakatat waves nating oscillations and surges that lasted for came from the open ocean. hours. In certain places maximum inundation An interesting aspect of these two records is occurred 5 or 6 hours later, at high tide. At that of the difference in amplitude and period Valdez, for example, the third wave came in at of the first waves to arrive at these two sites 2300, March 27, and the fourth one at 0145, which also supp orts the hypothesis of difference March 28 (Brown, 1964 ) . Thi s last wave took in origin (see Figs. 3 and 4). the form of a tidal bore and inundated the 306 PACI FIC SCIENCE, Vol. XXI, July 1967 8 7 6 5 4 3 en 2 0:: llJ ~ llJ ::E 0 -I -2 LEGEND -3 " ..... Projected tide after the earthquake -4 --Tide before earthquake -5 16 17 18 19 20 21 22 23 24 I 2 27-MARCH TIME IN HOURS -ALASKA STANDARD TIME 28-MARCH FIG. 3. Marigram of wave activity at the town of Yakutat. downtown section of Valdez, ruining almost all nega Island, inundating the village of Chenega the merchandise in the stores. These waves to an elevation of 15.5 m and completely de could not have come from the generating area stroying it. This same wave continued north outside Prince William Sound because if this through Knight Island Passage and inundated were so, it would have taken them only 34 Perry and Naked islands, but to lesser heights minutes to reach Valdez. It is more likely, then, (Berg et aI., in preparation) . that the waves at Valdez arrived in resonance Bathymetric surveys by the USCGS (1964) at high tide, from the immediate area of Port in the area off Montague Island and at the Valdez. north end of Latouche Island revealed a num Maximum positive crustal displacement in ber of large submarine slides. It is possible, Prince William Sound occurred along the north therefore, that the combination of submarine west coast of Montague Island and in the area slides and the tilting of the ocean floor due to offshore. These earth movements caused a gra uplift created the solitary wave reported at dient in hydrostatic level and the resulting Chenega village and at Perry and N aked islands. short-period wave raced through Knight Island A second wave about 40 m high (125 ft) Passage within 10 minutes and on toward Che- was reported coming out of the Valdez Narrows Alaska Earthquake and Tsunami, I-PARARAS-CARAYANNIS 307 I I I I I I I I I ., 8 7 6 - 5 , 4 , ! ~ ~~ : 3 ~ \ 1. I\1\1\" !,.. ' . V) a:: 1\ I\ ~III 1/ \ 1\ )...... 1LI2 1, t- III \ 111 U \ I \ ... '... .. ; :E,1LI I II! \ !~\II k. ...,./.. ...\...I, !\ f I ··.. \ \/111 . I. I 11 . v - : " \ I \,, I ~ V\ .v -: , ,' \ I, I o f----- I 1 (~ ~-- ~ - -- 1/- \'_1_' --1 i I ~\ \, \! -I 1/ \ / ~ ~ - ~ ~ LEGEND -2 • Observed ---Approximate water level -3 - -- --Hypothetical water level :...... Projected tide after the -4 earthquake --Tide before earthquake -5 I I I I I I II I I I 16 17 18 19 20 21 22 23 24 2 4 27-MARCH TIME IN HOURS-ALASKA STANDARD TIME 28-MARCH FIG. 4.Diagram of wave activity at Cape Yak ataga. and spread ing across the Sound (Plafker and log E(ergs) = 11.8 + 1.5 M (2) Mayo, 1965) . This wave was caused by slump The focal depth of the Alaska earthquake was ing of the glacial deltas in Port Valdez which about 20 km. This was shallow enough to create had been shaken loose by the force of the tsunami waves even though the epicenter of the earthquake. main shock was as much as 100 km inland from the coast. A number of shallower aftershocks TSUNAMI MECHANISM over a large area ranging from Hinchinbrook Most tsunamis result from earthquakes hav Island to southeast Kodiak Island indicate that ing focal depths of less than 60 km. Iida crustal movements over a wide area were in (1958) has derived an empirical relation giv volved. Undoubtedly these shallow aftershocks ing the maximum focal depth H ( in km ) for created smaller waves that could not be sepa an earthquake of magnitude M which has re rated, in the tide gauge records, from reflections sulted in a detectable tsunami : of the initial tsunami. If the tsunami waves that hit the island of M 6.42 0.01 H (1) = + Kodiak were the result of crustal movements where M is the Richter magnitude given by only, then the first wave could be expected to 308 PACIFIC SCIENCE, Vol. XXI, July 1967 be the highest, at least within the generating Geologic evidence has revealed a dipole pat area. At Uzinki, Kodiak City, W omen's Bay, tern of positive and negative tectonic move and elsewhere on the island of Kodiak, how ments resulting from this earthquake. The area ever, the third and fourth waves were the high of subsidence covers approximately 110,000 km2 est. A theory of generation from a single and the volume of crust that has been depressed pattern of crustal deformation is therefore not below its pre-earthquake level is about 115 km". satisfactory here. Such factors as reflection from The area of uplift covers about 105,000 km 2 coastal boundaries , wave interaction, and reso and includes the southern and eastern parts of nance should be taken into consideration. Prince William Sound, the coastal area as far Slumps or avalanches, similar to the ones that east as the Bering Glacier, and a great part of occurred in Prince William Sound , are usually the continental shelf and slope bordering the localized; they can produce no large tsunamis Gulf of Alaska. that would travel across wide portions of the The seaward limits of the area affected by ocean. According to Wiegel (195 4), not more the Alaska earthquake and the tsunami-generat than 2% of the potential energy of a fallin g or ing area were determined by means of a series sliding body is converted into wave energy. In of wave refraction diagrams as shown in Figure Prince William Sound, however, slumping and 5, based on Snell's Law of Refract ion. The sliding when added to tectonic movements cre tsunami-generating area covers 140,000 km2 ated tsunami waves of very large energy, but and includes the whole of the region of uplift their effect was catastrophic only locally; very and part of the region of subsidence. It extends little of the energy escaped the Sound . from the Trinity Islands to the Bering Glacier and includes Shelikof Strait, Cook Inle t, and SUMMARY AND CONCLUSIONS the continental shelf bordering the Gulf of Alaska to a depth of approximately 200 m. The The Alaska earthquake of March 27, 1964 total volume of displaced material in the tsu affected an area of approximately 215,000 krn-, nami-generating area was estimated to be 120 extending from the W rangell Mountains at the krn", and the energy associated with the tsunami northeast to the Trinity Islands in the south was calculated to be in the order of 6 X 1021 west, and from the west side of Shelikof Strait ergs. and Cook Inlet east to the vicinity of the Bering As a result of this work the following con Glacier. clusions are drawn: .... '110" ee· I--1----I--~___1---_1_---___t_;~~""--'----_j_-__:;~~M1r+t__\HHf--4-4---I_i'i-____i". ATTU l ~:;, .... .... ".. ,... ,... FIG. 5. Di agram of wave front's ief~acted toward the earthquake area from Attu Island (dashed line) , Adak Island (solid line) , and ,Unalaska Island (d otted line) . Alaska Earthquake and Tsunami, I-PARARAS-CARAYANNIS 309 1. Two main tsunami-generating areas can 7. In Prince William Sound two major tsu be distinguished: one along the continental namis were distinguished: one had its origin shelf bordering the Gulf of Alaska; the other near the west coast of Montague Island, the in Prince William Sound . other originated in the Port of Valdez. 2. The main generating area in the Gulf of 8. Two types of tsunami-generating mecha Alaska roughly corresponds to the geographic nisms were associated with the Alaska earth distribution of the major aftershocks. quake : (a) waves generated directly by tectonic 3, The energy of the tsunamis generated in movements of the sea floor, and (b) waves Prince William Sound was expended inside the generated indirectly from landslides, mudflows, Sound ; not much energy escaped this closed and slumping of alluvial deposits. region. 9. In Prince W illiam Sound both generation 4. The long period of the waves generated mechanisms were evident , while in the generat in the Gulf of Alaska is related to the long ing area along the Gulf of Alaska, the generated seiche period of the shallow shelf. tsunami was the direct result of tectonic move 5. The preferential radiation of energy to ments. ward the southeast is attributed to the orienta ACKNOWLEDGMENTS tion of the tectonic displacements along the continental shelf of the Gulf of Alaska. The work on which this paper is based was 6. The waves arriving at Cape Yakataga had supp orted in part by the National Science Foun their origin in .the shallow coastal area near the dation under the United States-Japan program Bering Glacier, whereas the waves arriving at for cooperative research in the Pacific, through Yakatat traveled through the deeper waters. grant N o. GF-1 53, and in part by the Office BERING , s ' « r > o Af TU l ~ ~A LAS KA '? " AL E UT \ A •• ;10 ~ .. , ..• . ~ ..o- 4 o.---+------h;:~~~_.;;:_~~---=T'_~==~-"""''__:::7''''h,?-_;7~~f_.A-+_--- 4 0 · 360_ 420- PALMY RA I. WA~t«J T O N l~ ~ I . ~ . 160 " E1BO· W 4BO FI G. 6. W ave refraction diagram of the Alaska tsunami for the north Pacific Ocean (time interval : 1) minutes) . 310 PACIFIC SCIENCE, Vol. XXI, July 1967 of Naval Research through contract Nom MENARD, H. W . 1964. Marine Geology of the 3748(03) . Pacific. McGraw-Hill Book Co., New York. I am particularly indebted to D . C. Cox, Pp. 97-116. W . M . Adams, and G. P. Woollard for their --- and R. S. DIETZ. 195 1. Submarine ge advice and constructive criticism. ology of the Gulf of Alaska . Bull. Geol. Soc. I would also like to acknowledge with appre Am. 62:239-253. ciation the advice, comments, and suggestions PLAFKER, G . 1965. Tectonic deformation asso given to me by A. S. Furumoto, K. Kajiura, ciated with the 1964 Alaska earthquake. Sci G. W . Groves, H. G . Loomis, G. R. Miller, ence 148 :1675-1687. and Robert Harvey. --- and L. R. MAYO. 1965. Tectonic De I also thank the members of the United formation, Subaqueous Slides and Destructive States-Japan Cooperative Field Survey (E . Berg, W aves Associated with the Alaskan March D . C. Cox, A. S. Furumoto, K. Kajiura, H. Ka 27, 1964 Earthquake: An Interim Geologic wasumi, and E. Shima) for permission to use Evaluation. U. S. Geol. Surv., Open File Rept. data from their report prior to publication. 19 pp. SHOR, G . G., JR. 1962 . Seismic refraction stud REFERENCES ies off the coast of Alaska : 1956-57. Bull. Geol. Soc. Am . 52 :37-57. BERG, E., D. C. Cox, A. S. FURUMOTO, K. U. S. COAST AND GEODETIC SURVEY. 1964. KA]IURA, H. KAWASUMI, and E. SHIMA. (In Preliminary Report, Prince William Sound, preparation.) Field Survey of the Tsunami of Alaskan Earthquakes; March-April 1964. 27 March 1964 in Alaska. Hawaii Inst. Geo 83 pp. phys. Rept. Series. VAN DORN, G. W. 1964. Source mechanism BROWN, D. L. 1964. Tsunamic Activity Accom of the tsunami of March 28, 1964 in Alaska . panying the Alaskan Earthquake of 27 March Chap. 10. In: Proc. N inth Conference on 1964. U. S. Army Engr. Dist., Anchorage, Coastal Engineering, Am . Soc. Civil Engr., Alaska. 20 pp. pp . 166-190. GRANTZ, A., G. PLAFKER, and R. KACHA WIEGEL, R. L. 1954. Laboratory studies of DOORIAN. 1964 . Alaska's Good Friday Earth gravity waves generated by the movement of quake March 27, 1964: A Preliminary Geo a submerged body. Univ. Calif. Inst. Engr. logic Evaluation. U. S. Geol. Surv. Circ. 491. Res., Ser. 3, Issue 362. 35 pp. WILSON, J. T. 1954. The development and IIDA, K. 1958. Magnitude and energy of earth structure of the crust. Chap. 4. In : Gerard P. quakes accompanied by tsunami, and tsunami Kuiper, ed., The Solar System, Vol. 2. The energy. J. Earth Sci., Nagoya Univ. 6 :10 i Earth as a Planet. Univ. of Chicago Press . 112 . WOOLLARD, G. P., N . A. OSTENSO, E. THIEL, JOHNSON, J. W ., P. O. O'BRIEN, and J. D . and W. E. BONINI. 1960. Gravity anomalies, ISAACS. 1948. Graphical construction of wave crustal structure, and geology in Alaska. J. refraction diagrams. H . O. Publ. No. 605. Geophys. Res. 65 :1021-1037.