inis.iaea.org...DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency

RECOMMENDED SEISMIC DESIGN

CRITERIA FOR HANFORD

NUCLEAR FACILITY

DR. GEO. W. HOUSNER

CALIFORNIA INSTITUTE OF TECHNOLOGY

UNDER

CONSULTANT AGREEMENT CA-00053

WITH

DOUGLAS UNITED NUCLEAR, INC.

OCTOBER 1, 1967

UlSTftstiUfKiK ‘Jf THtS DOCUMENT IS UHLMrES

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

DISCLAIM ER

Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

UNCLASSIFIED DUN-3130

97

RECOMMENDED SEISMIC DESIGN CRITERIAFOR HANFORD NUCLEAR FACILITY

By

Dr. George W. Housner

California Institute of Technology Under

Consultant Agreement CA-00053 With

Douglas United Nuclear, Inc.

October 1, 19^7... ^wciiuueni. Neither .... v'lmea states nor the United States Atomic Energy Commission, nor any of their employees, nor any of

their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights.

DOUGLAS UN/TED NUCLEAR, iNC.RICHLAND. WASHINGTON

NOTICETHIS REPORT WAS PREPARED FOR USE WITHIN DOUGLAS UNITED NUCLEAR,INC. IN THE COURSE OF WORK UNDER ATOMIC ENERGY COMMISSION CON

TRACT AT (45— I) - 1857, AND ANY VIEWS OR OPINIONS EXPRESSED IN THE

REPORT ARE THOSE OF THE AUTHOR ONLY. THIS REPORT IS SUBJECT TO

REVISION UPON COLLECTION OF ADDITIONAL DATA.

LEGAL NOTICETHIS REPORT WAS PREPARED AS AN ACCOUNT OF GOVERNMENT SPONSORED WORK.

NEITHER THE UNITED STATES, NOR THE COMMISSION, NOR ANY PERSON ACTING ON BEHALF OF THE COMMISSION:

A. MAKES ANY WARRANTY OR REPRESENTATION, EXPRESSED OR IMPLIED, WITH

RESPECT TO THE ACCURACY, COMPLETENESS, OR USEFULNESS OF THE INFORMATION CON

TAINED IN THIS REPORT, OR THAT THE USE OF ANY INFORMATION, APPARATUS, METHOD, OR PROCESS DISCLOSED IN THIS REPORT MAY NOT INFRINGE PRIVATELY OWNED RIGHTS; OR

B. ASSUMES ANY LIABILITIES WITH RESPECT TO THE USE OF, OR FOR DAMAGES

RESULTING FROM THE USE OF ANY INFORMATION, APPARATUS, METHOD, OR PROCESS DISCLOSED IN THIS REPORT.

AS USED IN THE ABOVE, ‘‘PERSON ACTING ON BEHALF OF THE COMMISSION^ INCLUDES

ANY EMPLOYEE OR CONTRACTOR OF THE COMMISSION, OR EMPLOYEE OF SUCH CONTRACTOR,

TO THE EXTENT THAT SUCH EMPLOYEE OR CONTRACTOR OF THE COMMISSION, OR EMPLOYEE

OF SUCH CONTRACTOR PREPARES, DISSEMINATES, OR PROVIDES ACCESS TO, ANY INFORMATION PURSUANT TO HIS EMPLOYMENT OR CONTRACT WITH THE COMMISSION, OR HIS EM

PLOYMENT WITH SUCH CONTRACTOR.

UNCLASSIFIED

UTStfttBttTtQK OF THIS DOCUMNT IS UNLM^IED54—5000—241 (12—65) AEC-RL.00 RICHLAND, WASH.

UNCLASSIFIED DUN-3130

RECOMMENDED SEISMIC DESIGN CRITERIA

FOR HANFORD NUCLEAR FACILITY

The Hanford nuclear facility, located in south-central Washington

State, consists of a number of reactors and their appurtenances0 The

reactors are in separate reinforced concrete buildings which may be

described as typical good quality eastern United States public utility

construction. This report contains recommendations for the seismic

safety of the Hanford facility. Two visits were made to the Hanford

area to inspect the facilities and the local geology. This report

is based largely on the information contained in the following reports

and publications:

a) Seismology Report on Washington, Idaho, Northern Oregon and Western Montana and the Hanford Area, Washington, by Norman H. Rasmussen, May 3, 1966.

b) Geology and Tectonic History of the Hanford Area, by Fred 0. Jones and Robert J. Deacon, June 15, 1966.

c) Geological Factors Relating to Engineering Seismology in the Hanford Area, Washington by Richard H„ Jahns, October 1, 1967.

d) Review of Hanford Reservation Soil and Geology, by Shannon and Wilson, Inc», September 1965.

e) Earthquake History of the United States, USC&GS, 1965.

f) Seismicity of the Earth, B. Gutenberg and C. F. Richter, Princeton University Press, 195^.

1. General Seismicity of the Area. The general seismicity of the

western United States, exclusive of California and western Nevada,

is indicated in Figure 1 which is a map prepared by the USC&GS, Two

north-south trending active seismic regions are indicated by the

clusters of earthquakes. One is along the western portion of

Washington including the Seattle-Tacoma-Olympia area; the other runs

down the western part of Montana into Colorado, Both of these areas

have experienced strong earthquake ground shaking, as evidenced by the

Seattle earthquake of April 13, 19^9, and the Hebgen Lake, Montana,

earthquake of August 17, 1959. Both of these were Magnitude 7,1 shocks.

UNCLASSIFIED

UNCLASSIFIED -2- DUN-3130

FIGURE 1

SEISMICITY OF WESTERN UNITED STATES

UNCLASSIFIED


The Hanford site, shown in Figure 1, is 'between these two relatively

active seismic zones in a region of lesser seismicity. On the basis

of the seismic history of the northwestern United States, Rasmussen

describes this area (lll+W to 121W)' as one of moderate seismicity.

Figure 2 is the USC&GS Seismic Probability Map (19^9) which shows the

Hanford region in Zone 2, verging towards Zone 1, whereas the Seattle

and the Hebgen Lake areas in Zones 3, In a general way, both Figure 1

and Figure 2 indicate that the site is in an area of moderate seismicity

(Zone 2) verging towards minor seismicity (Zone l). It is necessary,

however, to examine the detailed seismicity of the area and the geology

and tectonic activity of the area to see in what respects these corrobo

rate or modify the foregoing estimate of seismicity,

2, Detailed Seismicity of the Area, Figure 3 shows a plot of the

earthquake having instrumentally determined Magnitudes greater than

4,8, There are twenty-two of these shocks (Rasmussen) that occurred

between 1936 and 1965o Their Magnitudes were as follows; Tdj 7,1;

7,0; four at 6,0 to 6,4; seven at 5»5 to 6,0; five at 5,0 to 5,5; three

at 4,8 to 5,0, Only one of these occurred within 150 miles of the

site. This was the Milton-Freewater earthquake of July 15, 1936* which

had an assigned Magnitude of 5,7 - 5,8, This shock was located

approximately 60 miles southeast of the site (see Figure 3), Small

shocks, having Magnitudes less than 4,5, are more numerous.

If earthquakes with no instrumentally determined Magnitudes are

included, from 1865 to 1965, there are 114 shocks (Rasmussen) whose

epicentral ground motion was strong enough to be "felt by all; many

frightened and ran outdoors," These shocks presumably had Magnitudes

greater than about 4,5» They are plotted in Figure 4 where it is

seen that only two of them occurred within about 50 miles of the

site. One of these, the earthquake of March 6, 1893, is reported to

have caused some damage to buildings at Umatilla, Oregon, The other

shock, November 1, 1918, is described in Vol, 8, 1918 of the Bulletin

of the Seismological Society of America as, "The first shock was on

UNCLASSIFIED

UNCLASSIFIED

FIGURE 2

SEISMIC PROBABILITY MAP OF THE UNITED STATES

UNCLASSIFIED -L-

DUN-3130

UN

CLA

SSIFIED EARTHQUAKES WITH INSTRUMENTALLY DETERMINED MAGNITUDES I936-I965

UN

CLA

SSIFIED

-5- D

UN

-3130

UN

CLA

SSIFIED

FELT BY ALL; MANY FRIGHTENED AND RUN OUTDOORS.EVERYBODY RUNS OUTDOORS. DAMAGE NEGLIBIBLE IN BUILDINGS OF GOOD DESIGN AND CONSTRUCTION; SLIGHT TO MODERATE WELL BUILT ORDINARY STRUCTS

DAMAGE SLIGHT IN SPECIALLY DESIGNED STRUCTURES; CONSIDERABLE IN ORDINARY SUBSTANTIAL BUILDINGS WITH PARTIAL COLLAPSE . FALL OF BRICK CHIMNIES . (AFTER RASMUSSEN 1966)

FIGURE k

HISTORICAL EARTHQUAKES I865-I965

UN

CLA

SSIFIED

-6- D

UTT-3130

UNCLASSIFIED DUN-3130-7-

November 1st, between 9sl5 and 9s30 a


the area east of the Cascade Range to the Idaho border and south from

the east-west course of the Columbia River and its tributary, the

Spokane River, to the Oregon border. The basin province covers all of

this central and southeastern part of the state except for the south

east comer where the Blue Mountains of Oregon extend northward into

Washington, On the west, north and east, the basin is ringed by

mountains of diverse geologic elements; to the south the basin continues

for many miles into Oregon, The rock consists of a thick sequence of

basaltic lavas that have been folded by regional warping so that the

Columbia Basin now has the aspect of a broad structural basin centered

at Pasco (Near Hanford Reservation),"

Jones and Deacon conclude that, "Tectonic processes resulting in

major deformation of the earth’s crust follow major fault zones without regard to individual geologic or physiographic provinces. These zones can be identified on the earth’s surface by faults in the surface rocks. Persistently active tectonic zones can be identified by recurrent earthquake epicenters closely spaced along lineations which

are related to known and hidden faults, Hanford does not lie in a

zone of major tectonic deformation nor does it lie in a persistently active seismic zone,"

The foregoing conclusion is, in general, consistent with the estimate

of moderate seismicity in the Hanford region, Jones and Deacon, however,

cite evidence that might indicate the possibility of greater seismicity.

In particular, they note two fault systems in the Hanford area that

possibly have had surface displacement during historical times ^100

years). The first of these is the Saddle Mountain fault just north

of the site (shown in Figure 5)0 The second is the Rattlesnake

Mountain-Wallula-Milton-Freewater fault system, ten to eleven miles

south of separation plant sites (shown in Figure 5), The report by

Jahns describes the results of a follow-up investigation specifically

aimed at assessing the significance of these two geological features,

Jahns concludes "No evidence of recent or hisotric ground displacement

has been recognized along the trace of any fault in the Hanford region.

UNCLASSIFIED


•CORFU

SADDLE MOUNTAIN FAULT

YAKIMASITE

SNAKE RIVER

PASCO

YAKIMA RIVER

MILTON FREEWATER k ^ FAULT SYSTEM

MILTONFREEWATER

SCALE - MILES

FIGURE $

RELATION OF FAULTS TO THE SITE

UNCLASSIFIED


Features previously cited as constituting such evidence are significantly

different - in form, in attitude, and in location with respect to known

or inferred faults - from comparable features that do represent active

faults in other regions. All of them can be readily explained in terms

of genetic processes not necessarily associated with faults, and some

of them occupy ground where there is direct evidence against the

existence of faults," Jahns further states "It is recommended that

seismic design of structures within the Hanford nuclear facility be

compatible with the possibility of moderate to moderately strong ground

shaking from future earthquakes in the Pasco Basin 'and adjacent areas.

The distribution and nature of faults in the region suggest that a

local earthquake of Magnitude 5,5 is the strongest that could be

expected. The possibility of surface ground rupture due to upward

propagation of displacement along any fault in the Hanford facility

area is so remote that it can be safely disregarded,"

4, Foundation Materials. The foundation material at the site is

described as Glacio-Fluvial deposit of moderate depth having an

average seismic velocity of approximately 2000 ft, per sec, (Jones

and Deacon). This indicates a sufficiently firm material so that no

adverse seismic effects from it are anticipated and earthquake ground

motion having spectral characteristics similar to recorded California

ground motions on firm alluvium can be expected,

5, Engineering Significance of the Saddle Mountain Fault and the

Milton-Freewater Fault System, It is thought by Jones and Deacon, that

the 1918 Corfu earthquake originated on the Saddle Mountain fault. The

recorded description of the ground shaking at Corfu indicates only

moderate intensity. This evidence on shaking is not inconsistent

with the idea of Jones and Deacon. The foregoing would be consistent

with the occurrence of an earthquake having a Magnitude between 5,0 and

5,5, Since only moderate ground shaking was reported at Corfu, and

since the reactor plant sites are at a greater distance (10 to 15 miles)

from the Saddle Mountain fault than is Corfu (l to 3 miles) there would

be indicated a low intensity of shaking at the reactor plant sites.

UNCLASSIFIED


Low intensity of ground shaking would be expected in the event of an

earthquake having a Magnitude of 5.0 to 5.5 at a distance of 10 miles.

The occurrence of an earthquake of Magnitude 5.0 to 5.5 on the Saddle

Mountain fault would also be consistent with the general seismicity

of the area as shown in Figures 3 and 1+.

It is thought by Jones and Deacon that the earthquake of 1936 originated

on the Milton-Freewater fault system, Jahns concludes that this fault

system displays no evidence of surface movement during recent geological

time and that large earthquakes having Magnitude greater than about

5.5 are not expected to originate on it in the Pasco area. This is

consistent with the notion of moderate seismicity and the occureence

of earthquake of Magnitude about 5.5.

6, Recommended Design Earthquake. On the basis of the seismic record

it is estimated that the site experienced, during historical times, a

maximum ground acceleration less than 10$g; this would have been during

the 1918 Corfu earthquake. Although, according to the descriptions, the

1936 Milton-Freewater shock was larger than the Corfu shock, it was

centered approximately 60 miles from the site, and at this distance

the maximum acceleration for a Magnitude 5.8 shock would be less than

5$g. An earthquake similar to the 1936 Milton-Freewater shock occurring

along the northwest end of the fault would produce shaking at the site

approximately equivalent to a 15$g design spectrum. Accordingly, it

is recommended to base the earthquake design, using ordinary allowable

code stresses, on the Design Spectrum A,shown in Figure 6, which

corresponds to an acceleration of 17%g at zero period. This would be

consistent with the usual requirements for Zone 2 on the Seismic

Probability Map. For firm alluvium, not near a great fault, the Zone

requirements are usually considered to be as follows:

Zone 3 - 33%g

Zone 2 - l6%g

Zone 1 - 8%g

Zone 0 — k%g

UNCLASSIFIED

UN CLASSIFIED -12- DUN-3130

The recommendation of 17$g is on the conservative side when compared

with historical ^100 years) ground motions at the site.

Vertical and horizontal ground motion should he assumed to act

simultaneously and the spectrum for vertical motion should he 1/2 as

great as that for horizontal motion. This is consistent with calculated

spectra of recorded earthquakes.*

It should be noted that a design made on the basis of the 17%g spectrum

would have a factor of safety that would enable it to survive much

stronger ground motion. Actually, it would require ground motion more

than twice as severe as the 17$g spectrum to produce failure. This

factor of safety is to allow for the occurrence of larger earhtquakes

than those upon which the design is predicted, to allow for unforeseen

contingencies in the design and construction, etc. To insure an

adequate factor of safety the design should be such that the facility

will not release products hazardous to the public in the event of

ground shaking corresponding to the 30/£g spectrum B shown in Figure 7,

7o Method of Analysis and Design, For new critical structures, or

for new independent load-bearing elements of existing critical structures,

the design should be based on an elastic analysis (see TID-702^) and

ordinary allowable design stresses (no 33$ increase for transient loading)

as specified by the Uniform Building Code should be used. This

recommendation provides a conservative factor of safety.

Reasonable values of damping should be used as exemplified by the

following table;

17$g 30$gSpectrum Spectrum

Reinforced concrete shear wall building , 5$ 9$

Welded steel frame structure, 1$ 2$

Steel pipes with rigid supports , „ , , , 1$ 2$

*Chopra, A, K,, The Importance of the Vertical Component of Earthquake Motion, Bull, Seism, Soc, Amer„, Vol. 56, October 1966,

UNCLASSIFIED

(09S/U!) A

1D013A


n',2 .4 .6

PERIOD (secs)

FIGURE 6

DESIGN SPECTRUM - A

UNCLASSIFIED

VE

LOC

ITY

(in/s

ec)

UNCLASSIFIED -lU- DUN-3130

PERIOD (secs)

FIGURE 7

DESIGN SPECTRUM - B

UNCLASSIFIED


When strengthening the reactor buildings the existing stresses in

existing elements will not be known accurately so that special analysis

and design will be needed. Two different conditions will be encountered

At, The existing structural element is relatively weak and a new

element will be incorporated to carry all of the load. In

this case the above recommended method of analysis and design

should be used,

B, The existing structural element has considerable strength but

requires some strengthening. In this case, the design may be

such that failure will not occur in the event of ground motion

corresponding to a 30%g design spectrum. In the latter case,

steel may be stressed beyond the elastic limit and concrete

may sustain minor cracking,

8, Reactor Core, The reactors under consideration have graphite block

core structures containing the fuel rods and the control rods. The

blocks are keyed together but otherwise are free to expand and contract.

No recommendations are given here for the analysis and strengthening of

these structures. The complexity of these structures requires a special

study to evolve recommendations. It may be noted that the Japanese made

shaking table tests of a large-scale model of the graphite block core

of their Tokai power plant reactor before designing and constructing

the plant. Their experience may be used as a guide.

Prepared by

UNCLASSIFIED

UNCLASSIFIED APPENDIX DUN-3130Page l6

From 1841 to 1963 approximately 138 earthquakes of intensity V or greater centered in Washington and Oregon. Others were felt but centered either off shore in the Pacific, in British Columbia to the north, or in neighboring states. Most of the activity occurred in the western part of the region while the stronger shocks were in the neighborhood of Puget Sound. Indications are that the heaviest activity occurred in 1946 a few miles west of Tacoma and in 1949 near Olympia, Wash. A few of the earlier shocks may have equaled or possibly exceeded the 1946 shocks in intensity, but lack of detailed information prevents satisfactory comparison.

LIST OF EARTHQUAKES

Year Date Time Locality N.lat.

W.long.

Area(squaremiles)

IntensityM. M.

Authority

1841 16:00 0) V 32, 461856 48 123 3-25, 251859 02:30 (1) V 321860 48 123 0) 321864 18:10 48.5 123.5 VI 251865 August 25............ 21:00 48.5 123.5 VI 3-25, 251868 48 122 3-25, 251871 3-25,251872 150,000 VI 3-25, 25, 56

46.0 118.3 3-25, 25, 56January 4

1878 November 22__ 21:00 California, felt in Oregon.____ 42 124 70,000 VII 25, 28, 461877 09:00 VII 25, 461880 13:25 3-25, 25

December 12___ 20:40 VI 3-25, 251883 September 28__ 00:00 45.5 122.8 p) 3-25, 251885 08:00 47 123 V 3-25, 25

22:40 47.5 122.5 (2) v 251891 September 22__ 03:40 Port Angeles, Wash. .................. .. 48.0 123.5 (!) V 3-25, 25, 56

15:21 4,000 V-VI 3-25, 251892 20:30 10,000 VI 25, 46

14:50 47 123 VI 3-25, 251893 17:03 46 119 m VI-VII 25, 461895 04:47 46.5 122.4 V 3-25, 25

00:02 48 123 p) V-VI 3-9! 5, 9!K1896 22:15 VI 3-25, 25

21:55 48.3 124.3 (2) VI 3-2503:17 45.3 123.3 1,000 VI 9!5r

1897 47.8 120.0 4, 261903 18:15 47.7 122.2 10 000 V 3-251904 20:20 47 124 20,000 v 3-25r 561905 14:26 42.9 114.5 VII1906 05:45 7 000 VI 3-29, 56

05:12 38 123 375,000 XI 2fir 2Rr 5701:30 V 4601:10 41 124 « VII 8, 46, 2817:49 V 3-29, 4

1909 15:49 49.0 122.7 25,000 VII 3-25, 5609:20 47.6 120.0 (2) 822:45 40 M 124 100,000 VIII 28

1911 18:39 48.8 122.7 VI 3-251913 July 29................ 08:15 47 122 1,500 V 3-25

15:00 45.7 117.1 V 3-9, 46December 25___ 06:40 Puget Sound, Wash__ ________ 47.7 122.5 8,000 V 3-25

See footnotes at end of table

From: EARTHQUAKE HISTORY OF THE UNITED STATES, USC&GS, 1965

UNCLASSIFIED

UNCLASSIFIED APPENDIX DUN-3130Page 17

LIST OF EARTHQUAKES—Continued


W.long.

Area(squaremiles)

Intensity M. M.

Authority

1914 September 5___ 01:35 Olympia, Wash_______________ 47 123 1,000 V 3-251915 19:00 45.5 122.7 (*> Y 3-9, 46

06:05 48.5 121.4 VI 3-25, 56border.

10:00 48.5 121.4 30,000 V 3-251916 16:52 47.3 122.3 12,000 V 3-25

21:02 40M 119H 100,000 VI03:45 48.8 122.6 V 3-25

1917 09:05 46.8 122.0 (2) V 3-2506:30 46.8 122.0 (2) V 3-25

November 12___ 02:47 _____do___________________ ____ 46.8 121.8 1,000 VI 3-25November 13___ 18:57 46.8 121.8 (*) V 3-25

1918 February 28____ 15:45 Yakima, Wash________________ 46.5 120.5 m V 3-820:26 47.6 117.0 6,000 V22:47 46.5 121.7 (2) V 3-25

November 1____ 09:20 Corfu, Wash........ .......................... 46.7 119.5

UNCLASSIFIED APPENDIX DUN-3130Page l8

LIST OF EARTHQUAKES—Continued


W.long.

Area(squaremiles)

IntensityM. M.

Authority

1945 13:16 47.4 121.7 50,000 VI-VII 2700:46 47.4 121.7 VI 2712:46 47.4 121.7 V 27

1946 February 14____ 19:18 Puget Sound, Wash___________ 47.3 122.9 70,000 VII 2709:13 49.9 125.3 100,000 VIII 27

1948 14:35 V 271949 11:56 47.1 122.7 150,000 VIII 27

20:01 54 133 2,220,000 27, 561950 03:04 48 122% 7,000 VI 27

17:57 48.0 122.3 c1) v 271952 09:31 47.4 122.2 V 271953 December 15___ 20:32 Northwestern Oregon _______ 45.5 122.7 3,000 VI 271954 07:56 47.1 121.8 3,000 v 27

17:42 47.3 122.4 1,500 V 2705:02 47.4 122.3 17,000 VI 2705:42 V 27

July 6__________ 03:13 Western Nevada, felt in Oregon. 39.4 118.5 130,000 IX 2821:52 39.6 118.5 150,000 IX 28

December 16___ 03:07 _____do________________________ 39.3 118.2 200,000 X 28December 21___ 11:57 California, felt in Oregon_____ 40.8 124.1 50,000 VII 28

1955 02:20 47.8 124.0 V 27Wash.

22:56 48.0 122.0 8,500 VI 2708:53 48.4 124.6 V 2717:40 48.1 121.7 V 27

1956 20:30 47.3 122.4 2,500 v 2716:57 48.3 122.6 4,000 v 27

1957 17:16 48.3 122.4 15,000 VI 27February 11____ 09:05 47.5 121.1 4,000 VI 27

13:09 47.3 122.4 2,000 v 27November 1____ 02:12 Near Mount Rainier, Wash___ 47 121 1,500 V 27November 16___ 22:00 Northwest of Salem, Oreg___ 45.3 123.8 4,500 VI 27

1958 April 12________ 14:37 North-central Washington____ 48 120 8,000 VI 27July 9.................... 20:16 58.6 137.1 400,000 XI

21:00 v 2721:08 46.7 124.1 1,800 VI 27

1959 23:15 V 27(about)

15:53 45.7 122.3 600 v 27f 19:45 47.8 120.0 25,000 VI 27\ 20:36

13:36 47.8 122.0 2,800 v 27November 23___ 10:15 Near Longmire, Wash_________ 46.7 121.7 1,000 V 27December 11___ 22:24 Northwestern Washington_____ 48.7 123.3 8,000 V 27

1960 01:16 46.7 122.7 3,500 v 2722:48 47.5 122.3 600 VI 27

September 10__ 07:07 Northwestern Washington_____ 47.7 123.1 14,000 VI 271961 23:26 46.0 122.1 2,000 v 27

21:50 46.7 121.9 v 27Wash.

20:56 44.7 122.5 7,000 VI 27September 15__ 19:25 Southwestern Washington____ 46.0 122.2 7,000 VI 27September 16__ 03:45 Amboy, Wash_____ . ____ 46.0 122.2 V 27September 17__ 07:56 Southeast of Cougar, Wash 46.0 122.1 9,000 VI 27

19:35 48.4 120.0 1,200 v 27November 6____ 17:29 Northwest of Portland, Oreg___ 45.7 122.9 9,000 VI 27

13:30 V 271962 21:29 47.8 120.2 3,000 V 27

11:29 41.8 124.3 15,000 VI 27September 4___ 09:17 41.0 124.2 7,000 V 27November 5____ 19:37 Near Vancouver, Wash..____ 45.6 122.7 20,000 VII 27, 50December 31___ 12:50 West-central Washington___ 47.0 122.0 13,000 VI 27

1963 13:43 47.4 122.1 5,500 VI 2715:53 44.9 123.5 v 27

December 21___ 18:54 Okanogan County, Wash______ 48.3 119.3 3,000 V 27December 26 18:36 Northwestern Oregon 45.7 123.4 4,000 VI 27

1 Uncertain. 2 Local.

UNCLASSIFIED


INTERMEDIATE AND MINOR EARTHQUAKES

1841. December 2. Vancouver, Wash. Two shocks occurred after the eruption of Mount Baker. The first caused some unstable objects to fall. A loud report preceded or attended the shock and a roaring noise continued for some time. The second shock was undulatory, appeared to come from the west, and did some damage to a house foundation.

1856. December 26. Port Townsend, Wash. House jarred.1859. April 2. Crockery rattled and many were awakened in Olympia, Wash. The

Surveyor-General of the territory described its intensity as about equal to the effect of a sixty- mile per hour gale upon a frame house.

1860. May 7. Port Townsend, Wash. No details.1864. October 29. Strong shock at Victoria must have been strongly felt on Olympic

Peninsula, Wash.1865. August 25. Strong shock on Vancouver Island; probably felt strongly on Olympic

Peninsula, Wash.1868. May 30. Severe earthquake at Mukilteo and the Tulalip Reservation, Wash.1871. May 19. Shocks at Mount Rainier, in Washington Territory and along the coast

during the entire month.1872. December 14-16. At Olympia there was a severe shock at 21:40 on December 14,

followed by many others through December 16. At 09:18 on that date there was a shock, apparently most severe at Victoria, British Columbia. Very strong elsewhere in British Columbia. Dishes thrown from shelves at Seattle and slight damage at Olympia.

1872. December 16-January 4. A series of moderate shocks at Walla Walla, Wash.1873. November 22. A severe earthquake centering in northern California was felt from

San Francisco to Portland, Oreg. Nearly every building in Crescent City was damaged. Chimneys were damaged in many places as far north as Port Orford, Oreg. and east to Jacksonville, Oreg.

1877. October 12. Shock felt at Marshfield, Cascades, and Portland, Oreg. Chimneys thrown down in area.

1880. August 22. Earthquake felt at Port Townsend and Seattle, Wash., and on southern Vancouver Island. In Victoria, British Columbia plaster cracked and loose bricks fell.

1880. December 12. Strongest of shocks continuing from December 7 to December 29, and at intervals to March 14, 1881, apparently strongest at Bainbridge Island, Puget Sound, Wash. Felt from Victoria, British Columbia, to Portland, Oreg. There were four shocks in succession at Olympia.

1883. September 28. Two moderately strong shocks at Portland, Oreg.1885. October 9. Intensity V at Olympia, Wash.1885. December 8. Intensity V in Puget Sound region, Wash. Awoke sleepers at Olympia.

Three light shocks at East Sound; loud rumbling at Victoria, British Columbia.1891. September 22. Port Angeles, Wash. People wakened from sleep. Houses trembled.

Also felt at Victoria, British Columbia.1891. November 29. A strong shock was felt in the Puget Sound region. Epicenter

uncertain. Strong at Seattle, where an elevator jammed in the shaft and the waters of Lake Washington were disturbed. Also strong at Port Townsend, where people rushed from buildings, and at Pysht, where slight damage occurred.

1892. February 3. A severe shock at Portland, Oreg. Buildings swayed and terrified people rushed into the street. Strong vibration at Astoria, Salem, and Yaquina Head, Lake Harney.

1892. April 17. A shock whose epicenter was uncertain, but probably near Olympia, was sharply felt at Portland, Oreg. and at Tacoma, Wash. At Portland, people rushed into the street when buildings trembled.

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1893. March 6. Some damage to buildings at Umatilla, Oreg.1895. February 25. Eastern part of Cowlitz County, southwest Washington. Strongest

at Green River mines and along the Toutle River. Felt at Portland and Tacoma.1895. April 16. Port Townsend, Wash. Buildings trembled and many persons were

frightened.1896. January 3. At Port Angeles, Wash., lamp chimneys were shaken off and articles

tumbled from shelves. At Victoria, British Columbia, people hurried into streets.1896. February 6. A well-defined shock at East Clallam, Wash. Shook every house but

no damage. Felt at Neah Bay Reservation, Tatoosh Island and by vessel in Neah Bay.1896. April 2. At McMinnville, Oreg., three shocks in succession awakened everyone. The

shock was felt in Portland and Salem.1897. December 15. Lakeside, Wash. Severe. Felt at Waterville. Aftershocks through

December 20 and January 11-15, 1898.1903. March 13. Sand Point, Lake Washington, Wash. Two widely felt shocks felt at

Tacoma and Aberdeen.1904. March 16. Apparently strongest at Victoria, British Columbia, but widely felt over

western Washington.1905. November 11. A shock centering near Shoshone, Idaho was widely felt in eastern

Oregon.1906. January 2. Three shocks felt from south boundary of Spokane County, Wash, to

point north of Bradshaw, British Columbia. Felt at Colville, Davenport, and Grand Forks. Plaster fell at Nelson, British Columbia.

1906. April 18. This great California earthquake was sharply felt in southern Oregon. It was especially strong on soft ground at Paisley and Merrill.

1906. April 19. Strong enough to awaken people at Paisley, Oreg. Three additional shocks followed in 1% hours.

1906. April 23. An earthquake which threw down chimneys at Ferndale, Calif, was felt strongly at Grants Pass and Glendale, Oreg. where windows were broken and rumbling sounds heard. Also felt at Eureka, Calif.

1906. November 1. Shock centering near Colville, Wash., was felt over distance of 60 miles north-south and 70 miles east-west.

1909. January 11. Northwest comer of Washington. Cracks in walls at Blaine and plaster thrown down at Bellingham. Sidewalks twisted and piers slightly damaged at Anacortes. Felt at Olympia and Aberdeen.

1909. May 24. Dishes rattled and objects fell from shelves at Douglas and Waterville, Wash.

1909. October 28. This shock which was damaging in northern California was felt at Marshfield and Grants Pass, Oreg.

1911. September 28. Intensity VI at Victoria and IV at Bellingham, Wash.1913. July 29. Intensity V at Mount Rainier, Wash.1913. October 14. A strong earthquake in the Seven Devils District along the Oregon-

Idaho border broke windows and dishes.1913. December 25. Puget Sound, Wash. Two shocks felt at Seattle and Edmonds, Wash.;

second stronger.1914. September 5. At Olympia, Wash., there was a tremor followed by severe jolt. Felt

at Auburn, Tacoma, and other places.1915. May 18. A sharp local shock at Portland, Oreg. rattled dishes and rocked chairs.1915. August 18. Northwest Washington. Felt from Seattle to Laurier and from Vic

toria, British Columbia to Okanogan.1916. January 1. Puget Sound, Wash. Felt at Tacoma, Seattle, Olympia, and Silverton.

Buildings shook and doors moved.1916. February 2. Western Nevada shock felt in Oregon.1916. February 22. Marietta, Wash. Houses rocked, dishes rattled. Felt through south

west British Columbia and northwest Washington.1917. March 28. Shock felt on southwest slope of Mount Rainier and at Ashford, Wash.1917. June 9. Glenoma and Longmire, Wash. Shook buildings.

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1917. November 12. Mount Rainier, Wash. Rockslides at Longmire, Cedar Lake, and Summit Inn. A similar shock at Longmire Springs on November 13 (intensity V).

1918. February 28. Houses swayed at Yakima, Wash. Felt throughout Yakima Valley.1918. March 11. Shock centered near Rathdrum, Idaho. Felt in Spokane and other points

in eastern Washington.1918. June 20. Moderate at Longmire Springs near Mount Rainier, Wash.1918. November 1. Strong shock at Corfu, Wash, shook articles from shelves and caused

landslides.1918. December 6. A shock centering near Vancouver, British Columbia, was felt through

southern British Columbia and northwest Washington. Buildings shaken at Seattle. Magnitude 7.0.

1920. January 23. Northwest Washington and southwest British Columbia. Walls cracked at Bellingham and Anacortes. Epicenter probably under the Straits of Georgia. Strongly felt at Vancouver and Victoria, British Columbia. Some damage to houses on Vancouver Island. Several vessels felt the shock.

1920. April 14. Crater Lake, Oreg. Three shocks felt at Fort Klamath.1920. November 28-29. Fairly strong and widely felt shocks in Washington and Oregon,

apparently centering somewhere near Spokane.1921. February 25. Cascadia, Oreg. Felt by nearly all over an area of 6 by 12 miles.1922. January 31. Very strong submarine shock off northern California felt in south

western Oregon. Magnitude 7.6.1923. January 10. Lakeview and Klamath Falls, Oreg. Probably rather strong in un

settled region as it was widely felt. Plaster fell at Alturas, Calif.1923. February 12. Plaster broken in building in Bellingham, Wash. Two shocks at

Victoria, British Columbia. Felt at Marietta, Wash.1923. September (?) Sultan, Wash. Indefinite reports of a strong earthquake. No

accurate details but general agreement as to occurrence over wide area.1926. December 4. Epicenter probably in Straits of Juan de Fuca southwest of Victoria.

Strong at Bellingham, Wash, and Victoria, British Columbia. Felt sharply at Port Townsend and Port Angeles, Wash.

1926. December 30. Strongest at Wenatchee and Leavenworth, Wash, where people rushed into the street. Widely felt; epicenter uncertain.

1927. April 8. Shock in eastern Oregon widely felt over sparsely settled area. At Richland and Halfway entertainments were interrupted.

1928. February 2. Startup, Wash. Generally felt. Plaster cracked and people were alarmed.

1928. February 9. Strong on Vancouver Island, British Columbia. Fairly strong at Tatoosh Island with loud roar. Felt at Port Townsend, Wash.

1930. July 18. Shock near Perrydale, Oreg. Plaster cracked at McCoy. Roadbed cracked % mile west of Perrydale.

1931. April 17. Epicenter near Bellingham. At Acme a few bricks fell, and at Lawrence a severe twisting motion was observed. Felt slightly at Vancouver and Victoria, British Columbia.

1931. August 16. At Talent, Oreg., lamp was shaken from ceiling. Widely felt.1931. December 31. At Lilliwaup wall cracked, and at a number of places articles were

thrown from store shelves.1932. January 5. Near Sultan, Wash. Superficial damage at Monroe.1932. June 6. A strong submarine shock centering near Eureka, Calif, was widely felt in

southern Oregon at Klamath and Roseburg. Magnitude 6.4.1932. July 17. A widely felt shock centered near Sultan, Wash. No damage reported.1932. August 6. Strong local shock at Seattle, where a few chimneys were demolished and

others badly damaged.1932. August 6. Moderately strong shock at Sultan, Wash.

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1934. May 4. Puget Sound region. A sharp shock followed by numerous aftershocks. Furniture moved at Anacortes and Bellingham, Wash. People left theaters at Port Angeles. Also felt at Victoria and Vancouver, British Columbia.

1934. September 18. This was the first shock to attain intensity V of a series of local shocks at Ellensburg, Wash., which began on September 14 and continued till December 2. The series resembled the Helena, Mont, shocks of 1935 except that they were of much lower intensity. Other shocks of intensity V occurred on September 26 (2), October 19, and November 1 and 2. Effects were confined to movement of small objects, cracking of plaster, and slight damage to chimneys and cornices. Continued shocks terrified people who anticipated greater severity.

1934. November 3. A moderate shock east of the Puget Sound region probably reached intensity V. Felt most strongly at Rockport, Wash.

1935. July 9. Many frightened at Chelan Falls, Wash. Felt at Waterville.1936. July 15. Milton, Oreg. The earthquake was destructive at Freewater, State Line,

and Umapine, Oreg. At Freewater, plaster and windows were broken, chimneys were shifted at the roof line, and there was various damage to schoolhouses and other buildings. At Umapine walls and chimneys were cracked. At Walla Walla movable objects were shifted and a few chimneys were wrecked. In the central region there was much cracking of the ground, in one case over an area 1,500 by 75 feet. Some cracks were 200 feet long and water issued from many of them. The shock was felt over a large area in Washington, Oregon, and Idaho. Magnitude 5%. There were numerous aftershocks up to November 17. The two strongest attained intensity V on July 18 and August 4.

1936. August 27. Intensity V at Milton and Freewater, Oreg.1938. January 6. Epicenter probably in Puget Sound about 10 miles northwest of Seattle.

Felt strongest at Kingston, Port Orchard, and Seattle, where many were awakened and some frightened.

1939. November 12. Awakened populace generally and did some damage at Auburn, Brooklyn, Centralia, Elma, Oakville, Olympia, and Tacoma, Wash. Epicenter in mountains a few miles north and slightly west of Olympia. Affected area covered 60,000 square miles in Washington and Oregon. Also felt to some extent in Canada. Magnitude 5%.

1940. October 27. Puget Sound, Wash. Felt strongest in the Port Angeles-Port Town- send-Everett area. Also felt in Canada. No damage reported.

1941. February 9. Shock off northern California was felt in southwestern Oregon. Magnitude 6.6.

1941. April 7. Okanogan County, Wash. Furniture overturned at Mazama. Intensity V reported at Nespelem, Okanogan, and Omak.

1941. October 3. A sharp shock off northern California was felt in southwestern Oregon. Magnitude 6.4.

1941. December 29. Generally felt in Portland, Oreg. Some windows broken.1942. May 12. Corvallis, Oreg. Local shock strongly felt.1942. June 12. Dishes broken and table upset at Halfway, Oreg. Also felt at Baker,

Eagle Valley, Pine, and Richmond.1942. October 14. At Stehekin, Wash., boulder crashed down mountain, all awakened, and

plaster cracked. Also felt at Holden, Lucerne, and Mazama.1942. November 1. Plaster cracked at Portland, Oreg. Felt at Spokane, Wash.; Coeur

d’Alene, Idaho; and into Canada.1943. April 23. A sharp shock was felt by all or nearly all in Leavenworth and Entiat,

Wash. About 10,000 square miles in eastern Washington affected.1943. November 28. Puget Sound, Wash. Strongest at Richardson where chimneys

cracked. Also felt in British Columbia, Canada.1944. March 31. Sharp shock felt at Grapeview, Olympia, Orting, Shelton, and Tacoma,

Wash.1944. October 31. Felt by all in Entiat, Wash. Also felt at Chelan Falls, Lakeside,

Orondo, and Waterville.

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1945. April 29. Shock near North Bend, Wash, caused minor damage at North Bend, Palmer, Stampede Pass, and Cle Elum. Plaster, windows, and chimneys cracked. Large rockslides reported on west face of Mount Si. Muffled subterranean sound heard before and during shock. Felt area included most of Washington and small portions of Idaho and Oregon. Magnitude 5%.

1945. April 30. Aftershock of April 29 earthquake caused light damage at North Bend, Wash. Another aftershock on May 1 was widely felt in west-central Washington.

1946. February 14. Epicenter about 20 miles west of Tacoma, Wash. Light damage at Bremerton, Burton, Olympia, Seattle, and Tacoma. Greatest damage, estimated at $250,000, occurred at Seattle. The shock was felt in southwestern British Columbia and in northwestern Oregon. This was the strongest shock on record to center in the Seattle area.

1946. June 23. Epicenter in Georgia Strait, British Columbia. This was one of the strongest shocks on record for the Puget Sound area. Heavy damage occurred in the epicentral region. The bottom of Deep Bay in Georgia Strait was reported by the Canadian Hydrographic Department to have sunk from 9 to 84 feet. A 10-foot vertical ground shift occurred on Bead Island. Ground settlements up to 100 feet were noted at other points. South of the boundary in the State of Washington some chimneys fell at East Sound and a concrete mill was damaged at Port Angeles. It was felt strongly at Olympia, Seattle, Tacoma, Raymond, and Bellingham. Seattle, where tall buildings were damaged in the upper floors, was hardest hit in the Puget Sound area. Magnitude 7.3.

1948. September 24. Shock centering near Port Gamble, Wash, was felt throughout Puget Sound area, but caused no damage.

1949. April 13. Olympia, Wash. This earthquake caused heavy property damage over a wide area in Washington and Oregon. Eight persons were killed, many were injured, and total damage was estimated at about $25 million. At Olympia, nearly all large buildings were damaged, and water and gas mains were broken. A half-mile section of a 300-foot cliff toppled into Puget Sound near Tacoma. Many towns reported toppled chimneys, cracked walls and fallen plaster. Felt area extended eastward to western Montana and southward to Cape Blanco, Oreg. Magnitude 7.0.

1949. August 21. Queen Charlotte Islands. This shock, which did some damage near the epicenter, was felt as far south as Portland, Oreg. Small power lines and water mains broke in Seattle. Boats broke loose from moorings. Water level rose in Seattle lakes and sloshed from swimming pool in Tacoma. Magnitude 8.1.

1950. April 14. Epicenter near Langley, Wash. Many persons awakened in Coupeville, Langley, and Port Townsend. Plaster cracked and fell.

1950. December 2. Mukilteo, Wash. Sharp tremors were felt from 17:57 to 18:05. Stovepipes were shaken loose and dishes were broken.

1951. January 7. McNary, Oreg. Felt by and frightened many. Windows, doors and dishes rattled.

1952. August 6. Seattle, Wash. Plaster fell; old plaster cracks opened. Buildings creaked; loose objects rattled; and small objects swayed.

1953. December 15. Northwestern Oregon. Slight damage at Portland and Roy and at Vancouver, Wash.

1954. March 16. Shock centering near the Mud Mountains area of Mt. Rainier, Wash, was felt over 3,000 square miles of western Washington. Intensity V in parts of King and Pierce counties.

1954. May 4. Northwestern Washington. Shock was felt sharply at Tacoma, Wash, but caused no damage.

1954. May 15. Puget Sound, Wash. A moderately strong shock felt throughout northwestern Washington. Slight damage reported at Belfair, Lake Stevens, North Bend, Seattle, and Skykomish.

1954. May 23. Methow Valley, Wash. Sharp, brief shock at Winthrop and Twisp. Roaring sounds were heard.

1954. July 6, August 23, and December 16. A series of destructive shocks centering in western Nevada were widely felt in the western United States, including southeastern Oregon. Magnitudes 6.6, 6.8 and 7.1, respectively.

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UNCLASSIFIED APPENDIX DUN-3130Page 2k

1954. December 21. This intensity VII shock, which left $2,100,000 damage in the Eureka- Arcata, Calif, area, cracked plaster and concrete walls at Brookings, Oreg. Magnitude 6.6.

1955. January 11. Western Olympic Mountains, Wash. Intensity V at Port Angeles, where many persons were awakened and hanging objects swung. Also felt at Victoria, British Columbia and along the Strait of Juan de Fuca.

1955. March 25. Epicenter near Hartford, Wash. A house foundation near Everett was reported cracked. At Hartford, Monroe, Preston, and Sultan many persons were awakened by the shock. Windows, doors, and dishes rattled. Earth noises heard preceding shock.

1955. September 10. Neah Bay, Wash. Concrete buildings shook and small objects shifted. Also felt strongly on Tatoosh Island and at Clallam Bay.

1955. November 2. Shock northeast of Robe, Wash, was felt throughout Snohomish County. Principal effects were rattling of windows and dishes.

1956. January 6. Puget Sound, Wash. Intensity V at Burley, Dash Point, Dieringer, and Retsil. Windows and dishes rattled and small objects shifted.

1956. February 8. Northwestern Washington. Epicenter near the northwest corner of Whidbey Island. Maximum intensity V reported from communities in Skagit County. Weak aftershock at 17:29.

1957. January 25. Near mouth of Skagit River, Wash. Felt by many over an area of approximately 15,000 square miles of northwestern Washington. Plaster cracked at Clearlake.

1957. February 11. Near North Bend, Wash. Slight damage to plaster board and plaster at North Bend and Snoqualmie, respectively. Chimney cracked at Fall City.

1957. May 4. Puget Sound, Wash., near Dash Point. Trees, bushes shaken; windows, doors and dishes rattled. No damage.

1957. November 1. Near Mount Rainier, Wash. Felt over approximately 1,500 square miles of southwestern Washington, principally in Pierce and Lewis counties. Awakened many at Longmire, Packwood and Randle. Houses creaked; loose objects rattled.

1957. November 16. Northwest of Salem, Oreg. Frightened all at Salem. Plaster and walls cracked in west Salem; furnishings shifted.

1958. April 12. North-central Washington, about 8 miles southwest of Pateros. Slight damage reported consisting of cracked plaster; broken windows and dishes. Rocks slid onto roads near Chelan. Loud earth noises heard. A second shock was reported at Electric City (about 17:00 or 18:00) with about the same effects as the first shock.

1958. July 9. This major shock in southeastern Alaska was felt as far south as Seattle, Wash.

1958. August 22. Eastsound, Wash. (Orcas Island). Felt by several (some outdoors, active). Furnishings shifted.

1958. October 6. North end of Willapa Bay, Wash. Felt over approximately 1,800 square miles of Grays Harbor and Pacific counties. Patio cracked in several places at Tokeland. Moderate earth noises heard.

1959. January 20. Milton-Freewater, Oreg. Awakened many and frightened few. Pictures swayed. Also felt in Walla Walla, Wash. area.

1959. August 4. About 13 miles northeast of Portland, Oreg. in Washington. Felt over a limited area of Washington and Oregon, approximately 600 square miles. In Fairview, Oreg., pendulum clock stopped; small objects shifted. Sharply felt in downtown Portland area.

1959. August 5. Near Chelan and Chelan Falls, Wash. Minor damage at several localities. At Chelan, part of chimney and bricks fell; dishes broken. Chimney cracked and bricks loosened and fell at Waterville. Rockslides reported near Chelan and Waterville; many frightened. Severe shocks.

1959. October 14. Near Monroe on Mount Si Fault, Wash. Felt over approximately 2,800 square miles, principally on east side of Puget Sound. Felt by all at Monroe, Sultan, and Pine- hurst. Small objects shifted; loose objects rattled.

1959. November 23. Near Longmire, Wash. Awakened many at Ashford and Longmire. Windows and doors rattled; frame creaked.

1959. December 11. Northwest of Orcas Island, Wash. At Port Angeles windows broke; window cracked at Marysville.

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#1960. January 7. Southwestern Washington. Felt over 3,600 square miles, principally in

Lewis, Pierce, and Thurston counties. Many awakened and frightened. Small objects shifted. Houses creaked and loose objects rattled. Also felt at Portland, Oreg.

1960. April 10. About 6 miles southeast of Seattle city center, Wash. Felt over approximately 600 square miles of western Washington, principally in western King County. At Seattle, slight damage to concrete and wood walls; plaster cracked.

1960. September 10. Upper Duckabush River, near boundary between Olympic National Park and Olympic National Forest, Wash. Concrete basement floor and wall cracked at Bremerton. Considerable plaster cracking at Seattle.

1961. January 3. Epicenter 16 miles south-southeast of Mount St. Helens, Wash. (Skamania County). Felt over approximately 2,000 square miles of southwestern Washington, principally in Clark and Skamania counties. Felt by several and frightened few at Amboy; furnishings shifted. At North Booneville, awakened all in home.

1961. February 1. Epicenter a few miles west of Longmire in Mt. Rainier National Park,Wash. Felt by all at Longmire. Set off snow avalanches in mountains.

1961. August 18. Northwestern Oregon. Felt over approximately 7,000 square miles from southwest Lane County, Oreg. to Cowlitz County, Wash. At Lebanon, two chimneys toppled; windows broke; and traffic lights and signs fell. Plaster cracked at Albany. Generally felt.

1961. September 16. Southeast of Cougar, Wash, in Gifford Pinchot National Park. Felt over 7,000 square miles of southwestern Washington and northwestern Oregon. Felt by all and frightened many at Swift Dam. Knickknacks fell; trees, bushes shaken strongly. Intensity V at Corbett, Oreg.

1961. September 16. Amboy, Wash. Aftershock of September 15 (19:25). Felt by and frightened many. No damage.

1961. September 17. Southeast of Cougar, Wash, in Gifford Pinchot National Park. Principal aftershock of September 15 (19:25). Felt over 9,000 square miles of southwestern Washington and northwestern Oregon. Slight damage consisting of cracked chimneys, foundations and basement floor; old house shifted on foundation. Intensity VI in Oregon.

1961. October 30. Epicenter 17 miles west of Okanogan, Wash. Felt by all at Con- conully, Malott and Methow. No damage.

1961. November 6. About 15 miles northwest of downtown Portland, Oreg. Felt over approximately 9,000 square miles of northwestern Oregon and southwestern Washington. Felt by all throughout Portland area. Plaster cracked; part of chimney fell; and windows and lights broke.

1961. November 7. Oregon and Washington. At Portland, Oreg., television slid across floor; pictures tilted. Also felt at Vancouver and Washougal, Wash.

1962. January 14. Epicenter 16 miles due west of Chelan, Okanogan County, Wash., close to Navarre Coulee. Felt over 3,000 square miles of Chelan, Douglas and Okanogan counties of north-central Washington. Felt by all and awakened many in several towns. Plaster cracked at Malaga.

1962. August 23. Off Del Norte County coast, near Crescent City, Calif. Felt over 15,000 square miles of northwestern California and southwestern Oregon. Plaster, windows, walls, and chimneys cracked at Brookings and Cave Junction, Oreg. People fled into streets at Brookings. Intensity V at Grants Pass, Harbor, Merlin, Pistol River and Selma, Oreg.

1962. September 4. Northwest of Areata, Calif. Felt over 7,000 square miles of northwestern California. Intensity V reported at Cave Junction, Oreg. No details.

1962. November 5. Near Vancouver, Wash. Felt over an area of approximately 20,000 square miles of Washington and Oregon. Intensity VII in Portland where numerous chimneys were cracked or shaken down; windows broken; and large cracks in plaster. A loud noise and a thunderlike roar were reported. Minor damage was reported from several towns in Washington consisting principally of broken windows, cracked plaster and chimneys, and fallen bricks from chimneys.


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# UNCLASSIFIED APPENDIX DUN-3130Page 261962. December 31. Epicenter 5 miles due west of the northwest corner of Mt. Rainier

National Park, Wash. Slight damage consisting of cracked plaster, chimneys and walls; broken dishes; and twisted columns reported, mainly from Pierce County.

1963. January 24. Epicenter 2 miles due west of Maple Valley, Wash. Plaster and walls cracked at Maple Valley and Tacoma; furniture moved and objects fell to the floor.

1963. March 7. Northwestern Oregon, west of Salem. Felt from Portland south to Eugene and in some coastal areas. In west Salem area, plaster cracked and dishes broke.

1963. December 21. About 10 miles southeast of Omak, Wash. Felt over 3,000 square miles of Okanogan County, Wash. Felt by all at Malott, Loomis, Okanogan and Synarep. Moderately loud earth noises heard. Magnitude 4.4.

1963. December 26. Northwestern Oregon. Felt over an area of 4,000 square miles of northwestern Oregon and southwestern Washington. Plaster cracked at North Plains and Timber, Oreg. and at Toutle, Wash. Furniture shifted; books and pictures fell. Magnitude 4.5.

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