Earthquakes in the United States, July-September 1976

INTRODUCTION

The earthquake Information in this publication supplements that published in the NEIS (National Earthquake Information Service) publications, PDE ("Preliminary Determination of Epicenters") and "Preliminary Determination of Epicenters, Monthly Listing," to the extent of providing detailed felt and intensity data, as well as intensity and isoseismal maps for U.S. earthquakes. The purpose is to provide a complete listing of macroseismic effects of earthquakes, which can be used in risk studies, nuclear power plant site evaluations, seismicity studies, and answering inquiries by the public.

This publication contains two major sections. The first (table 1) is a tabular listing of earthquakes in chronological order by State, consisting of the following basic information: date, origin time, hypocenter, magnitude, maximum intensity, and computational source of the hypocenter. The second section consists of four maps and table 2, which lists detailed intensity information. The list of earthquakes in table 1 was compiled from those located in the United States or off the coasts that were published in the PDE; from hypocenters in California above magnitude 3.0, supplied by California Institute of Technology, Pasadena, the University of California, Berkeley, and other offices of the U.S. Geological Survey; from hypocenters in Hawaii supplied by the Hawaiian Volcano Observatory; and from any others that were felt or that caused damage, regardless of magnitude or availability of a hypocenter. Known or suspected explosions are also listed.

The intensities and macroseismic data were compiled from information obtained through questionnaires, from newspaper articles, and with the cooperation of other government agencies, State institutions, local organizations, and individuals. (See "Acknowledgments" for a list of collaborators.) The questionnaire (fig. 1A, B) is the latest revision of this form; it was not in use for earthquake-intensity evaluations for the years 1975-76. An interim version of the form and

Cl an earlier version that had been in use since the 1930's were the basis for intensity evaluations throughout 1976. Anyone wishing to submit felt or damage information on earthquakes for inclusion in future reports should send it to the National Earthquake Information Service, Stop 967, Box 25046, Denver Federal Center, Denver, Colo. 80225. Copies of the current "Earthquake Report" questionnaire can be obtained at this address.

collect macroseismic information is a questionnaire canvass using the "Earthquake Report" forms, which are mailed to postmasters in the area affected by the earthquake. The postmasters complete the forms and return them to the NEIS, where they are evaluated and an intensity value is assigned. The intensity observations are mapped and contoured by isoseismals. Isoseismal contours present a generalization of intensity data and an extrapolation of these data to regions from which there are no observations; they do not necessarily account for every individual observation.

"Earthquake Description" section of "United States Earthquakes," an annual publication, to which later data from other sources may be added for the purpose of updating and completeness. "United States Earthquakes" is published jointly by the U.S. Geological Survey, Department of the Interior, and the Environmental Data Service, NOAA, Department of Commerce.

and table 2 include the date, origin time, hypocenter (epicenter and focal depth), magnitude, intensity, and hypocenter source. The origin time and date are listed in Universal Coordinated Time (UTC) and local standard time based on the time-zone maps in figures 2 and 3. The epicenters, which were taken from those published in the PDE, or from other sources as noted, are listed here to two decimals. The accuracy of the The primary method used by the NEIS to

The data in table 2 will be included in the

DISCUSSION OF TABLES

The parameters for the earthquakes in table 1

C2

epicenters is that claimed by the institution supplying the hypocenter and is not necessarily the accuracy indicated by the number of decimals listed. The epicenters located by the NEIS have a varying degree of accuracy, usually two-tenths of a degree or less, depending on their continental or oceanic location. The oceanic hypocenters are less accurate than those on the continent, even though both are listed to two decimals. Depths are listed to the nearest whole kilometer.

Figures 4-6 are maps summarizing the earthquake activity for the conterminous United States, Alaska, and Hawaii for the period July-September 1976. The magnitudes plotted in these figures are based on ML or mbLg; if neither was computed, then on MS; and finally on mb, when it was the only magnitude computed.

The magnitude values listed in tables 1 and 2 were furnished by cooperating institutions or determined by the NEIS. The computational sources are labeled according to the assigned letter codes shown in headnotes to tables 1 and 2; the letter follows the value listed under the column heading "Magnitude." In table 1 the absence of a letter code indicates that the NEIS is the source. In table 2 the magnitude source is the same as the

C4 location source unless indicated otherwise, by an alphabetic character to the right of the magnitude value. The magnitude values calculated by the NEIS are based on the following formulas:

MS=log(A/T)+1.661ogD+3.3, (1)

as adopted by the International Association of Seismology and Physics of the Earth's Interior (IASPEI; Bath, 1966, p. 153), where A is the maximum horizontal surface-wave ground amplitude, in micrometers; T is the period, in seconds, and 18<T<22; and D is the distance, in geocentric degrees (station to epicenter), and 20°<D<160 0 . No depth correction is made for depths less than 50 km.

mb=log(A/T)+Q(D,h), (2)

as defined by Gutenberg and Richter (1956), except that T, the period in seconds, is restricted to 0.l£T<3.0, and A, the ground amplitude in micrometers, is not necessarily the maximum of the P-wave group. Q is a function of distance D and depth h, where 0^5°.

ML=logA-logA, (3)

as defined by Richter (1958, p. 340), where A is the maximum trace amplitude in millimeters, written by a Wood-Anderson torsion seismometer, and log A 0 is a standard value as a function of distance, where the distance is ^600 km. ML values are also calculated from other seismometers by conversion of recorded ground motion to the expected response of the torsion seismometer.

mbLg=3.30+1.66(logD)+log(A/T) 4°lDj<30 0 ,

as proposed by Huttli (1973), where A/T is expressed in micrometers per second, calculated from the vertical-component 1-second Lg waves, and D is the distance in geocentric degrees.

All of the intensity values (indicated by Roman numerals) listed in this summary were derived, using the Modified Mercalli Intensity Scale of 1931 (Wood and Neumann, 1931) shown below, from the evaluation of "Earthquake Report" forms; from field reports by U.S. Geological

C5

Survey personnel, engineering firms, or universities; and from detailed macroseismic data communicated to the NEIS by people in the area affected by the earthquake. All earthquake reports received which contain minimal information are assigned an Intensity II. These reports are filed in the offices of the NEIS or in government archives and are available for detailed study.

MODIFIED MERCALLI INTENSITY SCALE

Adapted from Sieberg's Mercalli-Cancani scale,

I. Not felt - or, except rarely under

OF 1931

modified and condensed.

especially favorable circumstances. Under certain conditions, at and outside the boundary of the area in which a great shock is felt: sometimes birds, animals, reported uneasy or disturbed; sometimes dizziness or nausea experienced; sometimes trees, structures, liquids, bodies of water, may sway doors may swing, very slowly.

n

II. Felt indoors by few, especially on upper floors, or by sensitive, or nervous persons. Also, as in grade I, but often more noticeably: sometimes hanging objects may swing, especially when delicately suspended; sometimes trees, structures, liquids, bodies of water, may sway, doors may swing, very slowly; sometimes birds, animals, reported uneasy or disturbed; sometimes dizziness or nausea experienced.

[II. Felt indoors by several, motion usually rapid vibration. Sometimes not recognized to be an earthquake at first. Duration estimated in some cases. Vibration like that due to passing of light, or lightly loaded trucks, or heavy trucks some distance away. Hanging objects may swing slightly. Movements may be appreciable on upper levels of tall structures. Rocked standing motor cars slightly.

IV. Felt indoors by many, outdoors by few.

Awakened few, especially light sleepers.

Frightened no one, unless apprehensive from previous experience. Vibration like that due to passing of heavy or heavily loaded trucks. Sensation like heavy body striking building or falling of heavy objects inside. Rattling of dishes, windows, doors; glassware and crockery clink and clash. Creaking of walls, frame, especially in the upper range of this grade. Hanging objects swung, in numerous instances. Disturbed liquids in open vessels slightly. Rocked standing motor cars noticeably.

V. Felt indoors by practically all, outdoors by many or most: outdoors direction estimated. Awakened many, or most. Frightened few slight excitement, a few ran outdoors. Buildings trembled throughout. Broke dishes, glassware, to some extent. Cracked windows in some cases, but not generally. Overturned vases, small or unstable objects, in many instances, with occasional fall. Hanging objects, doors, swing generally or considerably. Knocked pictures against walls, or swung them out of place. Opened, or closed, doors, shutters, abruptly. Pendulum clocks stopped, started or ran fast, or slow. Moved small objects, furnishings, the latter to slight extent. Spilled liquids in small amounts from well-filled open containers. Trees, bushes, shaken slightly.

VI. Felt by all, indoors and outdoors.

Frightened many, excitement general, some alarm, many ran outdoors. Awakened all. Persons made to move unsteadily. Trees, bushes, shaken slightly to moderately. Liquid set in strong motion. Small bells rang church, chapel, school, etc. Damage slight in poorly built buildings. Fall of plaster in small amount. Cracked plaster somewhat, especially fine cracks chimneys VII. Frightened all general alarm, all ran

VIII. Fright general alarm approaches panic.

IX. Panic general. Cracked ground

C8

in some instances. Broke dishes, glassware, in considerable quantity, also some windows. Fall of knick-knacks, books, pictures. Overturned furniture in many instances. Moved furnishings of moderately heavy kind.

outdoors. Some, or many, found it difficult to stand. Noticed by persons driving motor cars. Trees and bushes shaken moderately to strongly. Waves on ponds, lakes, and running water. Water turbid from mud stirred up. Incaving to some extent of sand or gravel stream banks. Rang large church bells, etc. Suspended objects made to quiver. Damage negligible in buildings of good design and construction, slight to moderate in well-built ordinary buildings, considerable in poorly built or badly designed buildings, adobe houses, old walls (especially where laid up without mortar), spires, etc. Cracked chimneys to considerable extent, walls to some extent. Fall of plaster in considerable to large amount, also some stucco. Broke numerous windows, furniture to some extent. Shook down loosened brickwork and tiles. Broke weak chimneys at the roof-line (sometimes damaging roofs). Fall of cornices from towers and high buildings. Dislodged bricks and stones. Overturned heavy furniture, with damage from breaking. Damage considerable to concrete irrigation ditches.

Disturbed persons driving motor cars. Trees shaken strongly branches, trunks, broken off, especially palm trees. Ejected sand and mud in small amounts. Changes: temporary, permanent; in flow of springs and wells; dry wells renewed flow; in temperature of spring and well waters. Damage slight in structures (brick) built especially to withstand earthquakes. Considerable in ordinary substantial buildings, partial collapse: racked, tumbled down, wooden houses in some cases; threw out panel walls in frame structures, broke off decayed piling. Fall of walls. Cracked, broke, solid stone walls seriously. Wet ground to some extent, also ground on steep slopes. Twisting, fall, of chimneys, columns, monuments, also factory stacks, towers. Moved conspicuously, overturned, very heavy furniture.

conspicuously. Damage considerable in (masonry) structures built especially to withstand earthquakes: Threw out of plumb some wood-frame houses built especially to withstand earthquakes; great in substantial (masonry) buildings, some collapse in large part; or wholly shifted frame buildings off foundations, racked frames; serious to reservoirs; underground pipes sometimes broken. X. Cracked ground, especially when loose and wet, up to widths of several inches; fissures up to a yard in width ran parallel to canal and stream banks. Landslides considerable from river banks and steep coasts. Shifted sand and mud horizontally on beaches and flat land. Changed level of water in wells. Threw water on banks of canals, lakes, rivers, etc. Damage serious to dams, dikes, embankments. Severe to well-built wooden structures and bridges, some destroyed. Developed dangerous cracks in excellent brick walls. Destroyed most masonry and frame structures, also their foundations. Bent railroad rails slightly. Tore apart, or crushed endwise, pipe lines buried in earth. Open cracks and broad wavy folds in cement pavements and asphalt road surfaces.

XI. Disturbances in ground many and widespread, varying with ground material. Broad fissures, earth slumps, and land slips in soft, wet ground. Ejected water in large amounts charged with sand and mud. Caused sea-waves ("tidal" waves) of significant magnitude. Damage severe to wood-frame structures, especially near shock centers. Great to dams, dikes, embankments often for long distances. Few, if any (masonry) structures remained standing. Destroyed large well-built bridges by the wrecking of supporting piers, or pillars. Affected yielding wooden bridges less. Bent railroad rails greatly, and thrust them endwise. Put pipe lines buried in earth completely out of service.

XII. Damage total practically all works of construction damaged greatly or destroyed. Disturbances in ground great and varied, 00.0 19.7 17.7 18 28 28.0 01 12 50.0 16 04 30.3 09 17 58.6 02 00 11.1 05 10 13.5 01 59 15.3 07 48 26.5 17 55 31.5 08 09 47.4

Table l.-SummaryofU.S. earthquakes for July-September 1976

63.23 N. 51.51 N. 51.30 N. 51.33 N. 63.56 N. 60.49 N. 61.91 N. 63.30 N. 59.93 N. 62.86 N. 53.95 N. 61.64 N. 62.70 N. 148.28 W. 179.15 W. 179.14 W. 179.16 W. 147.25 W. 147.83 W. 148.39 W. 150.80 W. 153.58 W. 150.68 W. 162.78 W. 146.36 W. 149.83 W. 33N 4.0 4.6 5.2 33N

4.5 4.6 33N 4.7 4.2

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numerous shearing cracks. Landslides, falls of rock of significant character, slumping of river banks, etc., numerous and extensive. Wrenched loose, tore off, large rock masses. Fault slips in firm rock, with notable horizontal and vertical offset displacements. Water channels, surface and underground, disturbed and modified greatly. Dammed lakes, produced waterfalls, deflected rivers, etc. Waves seen on ground surfaces (actually seen, probably, in some cases). Distorted lines of sight and level. Threw objects upward into the air.

3. OH 3.2M

<V ^ IS D^T^;

moN

Table l.-Summary of U.S. earthquakes for July-September 19 76-Continued

ii

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ii §11?: Si 11 5?:I 02 £:M: ffi \fafy jj. ::: SEPT: ... ... ... ... ii

Cll Table 1. -Summary of U.S. earthquakes for July-September 1976 -Continued

iii ii ii ii ii ii in ... in ... in ... ... in in ... in ... ... in ii ii ... iii ii ... ... ii ... in in

... ... ...V

C12 Table I.-Summary of U.S. earthquakes for July-September 7976-Continued Table 2.-Summary of macroseismic data for U.S. earthquakes, July-September 1976

5 July (G) Andreanof Islands, Aleutian Islands Origin time: 18 25 17.7 Epicenter: 51.30 N., 179.14 W. Depth: 61 km Magnitude: 4.6 mb Intensity II; Adak.

5 July (G) Andreanof Islands, Aleutian Islands Origin time: 18 28 28.0 Epicenter: 51.33N., 179.16 W. Depth: 54 km Magnitude: 5.2 mb Intensity II; Adak.

15 July (G) Central Alaska Origin time: Epicenter: Depth: Magnitude: Intensity IV;

22 July (G) Andreanof Islands, Aleutian Islands Origin time: Epicenter: Depth: Magnitude: Intensity II;

30 July (G) Southern Alaska Origin time: 13 54 32.2 Epicenter: Depth: Magnitude: Intensity II;

11 August (G) Andreanof Islands, Aleutian Islands Origin time: Epicenter: Depth: Magnitude: Intensity III;

16 August (G) Andreanof Islands, Aleutian Islands Origin time: 05 11 38.9 Epicenter: 51.50 N., 178.38 W. Depth: 65 km Magnitude: 5.1 mb Intensity II; Adak.

08 09 47.4 62.70 N., 149.83 W. 24 km 4.2 mb, 4.6 ML(M) Talkeetna.

14 30 17. 51.49 N., 177.86 W. 58 km 4.9 mb Adak.

61.33 N., 147.44 W. 40 km 3.9 mb, 4.0 ML(M) Valdez.

20 43 45.5 51.70 N., 175.42 W. Normal 4.6 mb Adak.

C14 Table 2.-Summary of macroseismic data for U.S. earthquakes,

16 August (G) Andreanof Islands, Aleutian Islands

22 August (G) Southern Alaska

25 August (G) Kenai Peninsula

July-September 7976-Continued

Origin time: 10 11 33.3 Epicenter: 51.49 N., 178.05 W. Depth: 55 km Magnitude: 4.8 mb, 3.9 MS Intensity II; Adak.

Origin time: 02 01 47.4 Epicenter: 60.22 N., 153.30 W. Depth: 144 km Magnitude: 5.5 mb

An observer near the epicenter noted:

Campers at the west end of Kontrashibuna Lake, at about 60.15 N., 153.90 U., heard a loud noise to the southeast, looked immediately in that direction, but saw nothing. Experienced mountaineers in the group agreed later that it sounded like a rock avalanche, and that if it had been a rockfall they would have seen it. Less than a minute later they saw a 5-8 cm swell on the lake reach the shore where they were camped, even though it was a windless day. Five to eight cm waves continued to break on the shore from many directions for several minutes before beginning to subside. The water was murky for at least one-half hour afterward. None of the campers felt any indication of earth movement.

Intensity VI; Kenai (small ground cracks unconfirmed), Ninilchik (small objects fell, not broken). Intensity V; Anchorage (small objects moved, many people frightened), Anchor Point, Clam Gulch, Homer, Kasilof (surface of water disturbed, small objects moved), Nondalton (observer drifting in small boat on Snowshoe Bay felt vibration), Port Graham, Port Lions, Seward (small objects moved), Soldotna, Sterling (observer picking berries felt shaking "longer than two minutes"), Was ilia. Intensity IV: Aniak, Chugiak, Nyac, Old Harbor, Ouzinkie, Seldovia, Talkeetna. Intensity III; Mill Bay, Kodiak, Palmer (M).

Origin time: 11 04 18.9 Epicenter: 60.61 N., 150.17 W. Depth: 47 km Magnitude: None computed. Intensity III; Anchorage, Northern Kenai Peninsula.

Table 2.-Summary of macroseismic data for U.S. earthquakes,

Intensity II; Adak.

15 September (G) Southern Alaska Origin time: Epicenter: Depth: Magnitude: Intensity II:

21 September (G) Kodiak Island region Origin time: 03 01 04.6 Epicenter: Depth: Magnitude: 4.9 mb, 4.6 ML(M) Intensity III; Kodiak.

22 September (G) Andreanof Islands, Aleutian

Origin time:

Epicenter:

Depth:

Magnitude:

Intensity IV; Adak.

27 September (G) Southern Alaska Origin time: Epicenter: Depth: Magnitude: Intensity III;

25 September (S) Northeastern Arkansas Origin time; Epicenter: Depth: Magnitude: JLntensity V;

Intensity IV;

Intensity II;

July-September /976-Continued

Arkansas Lepanto, Payneway, Trumann, Tyronza. Tennessee Macon, Memphis.

Arkansas Marked Tree, Riverdale. Missouri Deering.

Arkansas Hunter, Swifton. 178.77 W.

16 44 29.6 61.08 N., 150.62 W. 74 km None computed. Anchorage.

57.84 N., 152.12 W. Normal

02 30 25.7 51.72 N., 175.95 W. 43 km 4.8 mb, 5.1 MS

05 59 45.7 60.46 N., 145.17 W. 41 km 4.0 mb, 3.3 ML(M) Cordova.

14 06 56.0 35.61 N., 90.45 W. 5 km 3.6 mbLg

Table 2.-Summary of macroseismic data for U.S. earthquakes,

6 July (G) Northern California

7 July (B) Central California

July (B) Northern California

13 July (B) Northern California

July-September 7976-Continued

Origin time: Epicenter: Depth: Magnitude: Intensity V; Intensity IV; Intensity II;

Origin time: 03 55 16.2 Epicenter: 39.40N., 121.60 W. Depth: 5 km Magnitude: 4.5 mb, 4.1 ML(B) Intensity V; Camptonville, Dobbins, Fair Oaks, Forbestown, Oroville, Marysville. Intensity IV; Bangor, Browns Valley, Chico, Colfax, Grass Valley, Gridley, Loomis, Meadow Vista, Nevada City, Rackerby, Rio Oso, Sheridan, Smartville, Weimar, Wheatland. Intensity III; Strawberry Valley, Sutter, Trowbridge. Intensity II: Meridian, Richvale, Sacramento (press report), Twain, Yuba City (press report).

Origin time: 07 50 45.4 Epicenter: 37.44 N., 121.77 W. Depth: 10 km Magnitude: 3.5 ML

A power outage for 20,000 residents of Santa Clara County that lasted 2 hours occurred at the time of the quake (press report).

Intensity IV: Mt. Hamilton, San Jose, Sunnyvale, Willow Glen (press report). Intensity III; Campbell (press report), Fremont (press report), Santa Clara (press report).

Origin time: 16 14 10.5 Epicenter: Depth: Magnitude: Intensity IV;

Origin time: 13 34 53.7 Epicenter: 38.09 N., 121.87 W. Depth: 10 km Magnitude: 3.6 ML

Felt throughout sections of Contra Costa, Sacramento, and Solano Counties (press report). 19 45 20.4 40.39 N., 120.58 W. 5 km 4.4 mb(G), 3.8 ML Litchfield. Strawberry Valley. Janesville, Susanville.

40.10 N., 124.00 W. 2 km 2.9 ML Petrolia.

Table 2.-Summary of macroseismic data for U.S. earthquakes,

Intensity V;

Intensity IV;

Intensity III; Antioch, Collinsville (press

Intensity II; Bethel Island (press report),

18 July (B) Central California Origin time: 11 49 28.4 Epicenter: 37.28N., 122.17 W. Depth: 10 km Magnitude: 2.6 ML Intensity V; Los Altos Hills (stained glass

23 July (P) Southern California Origin time: Epicenter: Depth: Magnitude: Intensity IV;

Intensity III; Bellflower (press report),

26 July (B) Northern California Origin time: 13 50 05.0 Epicenter: 36.37 N., 121.17 W. Depth: 6 km Magnitude: 2.3 ML Intensity IV; Pinnacles National Monument

26 July (B) Northern California Origin time: 14 00 01.7 Epicenter: 36.55 N., 121.17 W. Depth: 6 km Magnitude: 2.0 ML Intensity IV; Pinnacles National Monument

1 August (P) Southern California Origin time: Epicenter: Depth: Magnitude: Intensity V; Intensity IV; Intensity II;

2 August (G) California-Nevada border region Origin time: Epicenter: Depth: Magnitude: Intensity IV; Intensity II;

9 August (P) Southern California Origin time: 10 54 30.0

California Continued California Continued

Vista.

report).

Byron, Concord, Fairfield (press report), Hood, Martinez, Ryde, Walnut Creek.

windows cracked press report).

lamps press report).

Compton (press report), North Long Beach (press report).

(east side, headquarters area).

(east side headquarters area).

Pittsburg.

Birds Landing, Diablo, Rio

20 53 55.9 33.87 N., 118.13 W. 11 km 3.1 ML Lakewood (shook desk

17 18 48.1 34.90 N., 116.58 W. 12 km 4.5 ML Daggett, Newberry Springs. Landers, Yermo. Baker.

08 14 07.4 38.38 N., 118.19 W. 8 km 4.8 mb, 4.3 ML(B) Luning, Mina. Hawthorne.

Table 2.-Summary of macroseismic data for U.S. earthquakes,

11 August (P) Southern California

July-September 7976-Continued

Epicenter: Depth: Magnitude: Intensity II;

Origin time: 15 24 55.5 Epicenter: 33.48 N., 116.51 W. Depth: 15 km Magnitude: 4.3 ML

An area around the epicenter having a radius of 200 km was canvassed and 642 questionnaires were mailed. The quake was felt in San Bernardino, San Diego, Orange, and Imperial Counties, over an area of approximately 15,500 sq km, as shown in figure 7.

Intensity VI; Borrego Springs (ground cracked in "fault wash" in east part of Anza-Borrego State Park; also some mudslides reported by acting manager of State Park), Indio (slight damage; one resident became nauseous press report), Palm Desert (cement curb raised 5 cm, causing buckling).

Intensity V; Angelus Oaks (postmaster sitting in car in parking lot reported, "The trees and surrounding area...made a strange sound as if the wind were blowing. The animals and birds were very still, and the building creaked somewhat. My vehicle bounced...for about 30-40 seconds and then began to slow down as the suspension stopped the vibrations."), Anza, Big Bear City, Cathedral City, Hemet, Idyllwild, Laguna Niguel (report from observer on fifth floor of six-story Federal Building stated that 13 of 18 people felt the shock. Duration was estimated to be 2-3 seconds, with two shocks 8-10 seconds apart. Hanging planters and pictures swung from east to west. Some people frightened; some became dizzy), North Palm Springs, Potrero, Ranchita (small objects displaced), San Diego, San Jacinto, San Luis Rey Downs, Thousand Palms, Warner Springs. Intensity IV; Alpine (goats reacted before the earthquake), Cabazon, Coachella, Escondido, Julian, La Quinta, Mead Valley, Mecca, Moreno, Morongo Valley, Mountain Center, Muscoy, North Shore, Pala, Palm Springs, Rancho Mirage, Salton City, Temecula, Thermal, White Water, Winchester, Yucca Valley. Intensity III; Cuyamaca (felt at caretaker's home, on State Highway 79 at south end of Cuyamaca Dam), Murrieta, Riverside, Santa Ysabel. Intensity II; Bonsai1, Homeland, North Park. 34.33 N., 118.52 W. 8 km 2.8 ML Northridge.

Table 2.-Summary of macroseismic data for U.S. earthquakes,

12 August (B) Central California Origin time: 08 51 11.3 Epicenter: Depth: Magnitude: Intensity IV;

15 August (B) Central California Origin time: 12 29 05.6 Epicenter: 37.79 N., 121.96 W. Depth: 7 km Magnitude: 3.3 ML

July-September 7976-Continued

California Continued California Continued

(windows rattled at headquarters building; light fixtures squeaked but did not swing) Storrie (windows rattled).

Table 2.-Summary of macroseismic data for U.S. earthquakes,

37.17 N., 121.53 W. 7 km 3.2 ML Pinnacles National Monument

July-September 7976-Continued

The press reported that seven quakes occurred within 2 1/2 hours after this shock near Danville in Contra Costa County.

Intensity V; Alamo, Castro Valley, Diablo (3 tremors felt from 3 a.m. to 5 a.m.), San Lorenzo. (Many were awakened and frightened in these communities.) Intensity IV; Danville (press report), Walnut Creek (radio station reported windows shattered in one house unconf irraed). Intensity II; Dimond, Oakland Airport.

Table 2.-Summary of macroseismic data for U.S. earthquakes,

16 August (F) Califonia-Nevada Border Region Origin time: Epicenter: Depth: Magnitude: Intensity V: 20 August (B) Central California Origin time: 22 05 52.9 Epicenter: 37.79 N., 121.97 W. Depth: 7 km Magnitude: 4.0 ML

Felt throughout the San Francisco Bay area.

Intensity IV; Alameda, Danville, Dublin

Intensity III; Berkeley (press report), El

Intensity II; Daly City, Dimond, Hayward,

20 August (B) Central California Origin time: 22 08 01.1 Epicenter: 37.76 N., 121.91 W. Depth: 2 km Magnitude: 3.8 ML Felt throughout the San Francisco Bay area.

Intensity IV;

22 August (P) Southern California Origin time: Epicenter: Depth: Magnitude: Intensity IV; Intensity III; Fontana (press report), San

1 September (B) Northern California Origin time: 22 42 48.8 Epicenter: 40.64 N., 122.21 W. Depth: 5 km Magnitude: 3.5 ML Intensity IV; Central Valley, French Gulch,

Intensity III; Millville.

Intensity II; Anderson.

5 September (B) Central California Origin time: 03 15 09.3 Epicenter: 37.60H., 121.43 W. Depth: 9 km Magnitude: 3.5 ML Intensity IV; Tracy (floors and walls

July-September 19 76 -Continued

California Continued California Continued

(press report).

Cerrito, Walnut Creek.

Martinez, Oakland, Pittsburg, Pleasanton, San Francisco, San Ramon, Sunol. (All press reports except Dimond.)

The preceding earthquake was canvassed. Only one respondent mentioned that the same effects were felt for both shocks.

report).

Bernardino (press report).

Lakehead, Palo Cedro, Project City, Red Bluff (press report), Redding.

shook). 16 37 21.4 36.19 N., 117.66 W. 8 km 3.7 ML(B), 3.7 ML(P) Darwin.

08 09 59.7 34.05 N., 117.47 W. 3 km 3.0 ML Etiwanda.

Table 2.-Summary of macroseismic data for U.S. earthquakes,

12 September (B) Northern California

16 September (B) Central California

24 September (P) Southern California

13 September (B) Northern California

All the intensities listed below, unless indicated otherwise, were assigned by the Hawaiian Volcano Observatory.

2 July (H) Island of Hawaii

8 July (H) Island of Hawaii

8 July (H) Island of Hawaii

July-September 19 76 -Continued

Origin time: 17 34 33.0 Epicenter: 37.90N., 122.22 W. Depth: 6 km Magnitude: 2.5 ML Intensity II; Martinez.

Origin time: 12 37 12.0 Epicenter: Depth: Magnitude: Intensity II;

Origin time: Epicenter: Depth: Magnitude: Intensity II;

California Off the coast

Origin time: Epicenter: Depth: Magnitude: Intensity IV; Intensity III; Rio Dell.

Origin time: Epicenter: Depth: Magnitude: Intensity II;

Origin time: Epicenter: Depth: Magnitude; Intensity II;

Origin time: Epicenter: Depth: Magnitude: Intensity III; Intensity II; 37.34 N., 121.77 W. 2 km 2.5 ML San Jose.

14 02 17.6 34.07 N., 118.15 W. 8 km 2.2 ML Downtown Los Angeles area.

16 08 10.2 40.20 N., 124.39 W. 1 km 4.8 mb(G), 4.0 ML Ferndale, Petrolia, Scotia,

15 57 37.8 19.26 N., 155.53 W. 9 km 2.6 ML Pahala.

03 49 06.6 19.40 N., 155.26 W. 5 km 2.5 ML Hawaii National Park.

07 39 17.0 19.39 N., 155.26 W. 7 km 2.7 ML Hawaii National Park. Volcano.

Table 2.-Summary of macroseismic data for U.S. earthquakes, July-September 19 76 -Continued

Hawaii Cont inued Hawa ii Cont inued

12 July (H) Island of Hawaii Origin time: 09 26 10.7 Epicenter: 19.35 N. , 155.22 W. Depth: 10 km Magnitude: 3.2 ML Intensity II: Volcano.

12 July (H) Island of Hawaii Origin time: Epicenter: Depth: Magnitude: Intensity II; Hawaiian Volcano Observatory,

14 July (H) Island of Hawaii Origin time: Epicenter: Depth: Magnitude: Intensity III; Intensity II;

15 July (H) Island of Hawaii Origin time: 00 14 38.1 Epicenter: Depth: Magnitude: Intensity II:

15 July (H) Island of Hawaii Origin time: 18 54 39.8 Epicenter: Depth: Magnitude: Intensity II; 16 July (H) Island of Hawaii Origin time: Epicenter: Depth: Magnitude: Intensity II; 22 July (H) Island of Hawaii Origin time: Epicenter: Depth: Magnitude: Intensity III; Intensity II;

23 July (H) Island of Hawaii Origin time: Epicenter: Depth: Magnitude: Intensity III; Intensity II; 24 July (H) Island of Hawaii Origin time: 05 38 17.0 Epicenter: 19.34 N., 155.14 W. Depth: 9 km Magnitude: 3.7 ML Intensity II; Kurtistown, Naniwale, Volcano.

22 45 35.2 19.38 N., 155.25 W. 5 km 3.0 ML

12 05 02.3 19.39 N., 155.24 W. 6 km 3.3 ML Hawaii National Park. Volcano.

19.37 N., 155.21 W. 6 km 3.2 ML Volcano.

19.36 N., 155.13 W. 8 km 3.3 ML Hilo.

11 11 28.6 19.19 N., 155.55 W. 10 km 3.2 ML Pahala.

12 40 53.0 19.38 N., 155.08 W. 9 km 3.7 ML Hilo. Mountain View, Papaikou.

07 49 45.4 19.39 N., 155.25 W. 5 km 3.3 ML Hawaii National Park. Volcano.

Table l.-Summary of macroseismic data for U.S. earthquakes,

25 July (H) Island of Hawaii

27 July (H) Island of Hawaii

28 July (H) Island of Hawaii

30 July (H) Island of Hawaii

30 July (H) Island of Hawaii

30 July (H) Island of Hawaii

31 July (11) Island of Hawaii

1 August (H) Island of Hawaii

July-September 797<J-Continued

Origin time: 06 53 44.1 Epicenter: 19.38 N. , 155.12 W. Depth: 9 km Magnitude: 2.9 ML Intensity II: Glenwood.

Origin time: 17 14 26.8 Epicenter: 19.37 N., 155.09 W. Depth: 9 km Magnitude: 4.0 ML Intensity III; Hilo. Intensity II; Glenwood, Kurtistown, Mountain View, Papaikou, Volcano.

Origin time: 06 37 12.7 Epicenter: 19.39 N., 155.24 W. Depth: 5 km Magnitude: 3.6 ML Intensity III; Hawaii National Park, Hawaiian Volcano Observatory. Intensity II; Volcano.

Origin time: 08 46 35.2 Epicenter: Depth: Magnitude: Intensity II;

Origin time: 15 09 43.6 Epicenter: 19.34N., 155.11 W. Depth: 8 km Magnitude: 3.8 ML Intensity III: Hilo. Intensity II; Keaau, Mountain View.

Origin time: 18 02 34.9 Epicenter: Depth: Magnitude: Intensity II;

Origin time: 09 19 13.9 Epicenter: Depth: Magnitude: Intensity II;

Origin time: 02 51 36.0 Epicenter: 19.41 N., 155.27 W. Depth: Magnitude: Intensity III: Hawaii National Park. Intensity II; Volcano. 19.37 N., 155.25 W. 6 km 3.0 ML Hawaii National Park, Volcano.

19.34 N., 155.12 W. 9 km 2.7 ML Hilo.

19.34 N., 155.20 W. 9 km 3.0 ML Volcano.

5 km 3.3 ML

Table 2.-Summary of macroseismic data for U.S. earthquakes, July-September 7976-Continued

2 August (H) Island of Hawaii Origin time: 01 01 17.4 Epicenter: 19.37N., 155.09 W. Depth: 9 km Magnitude: 3.4 ML Intensity III: Hilo.

2 August (H) Island of Hawaii Origin time: 02 39 18.0 Epicenter: 19.39M., 155. 25 W. Depth: 6 km Magnitude: 3.6 ML Intensity III: Hawaii National Park.

2 August (H) Island of Hawaii Origin time: 16 37 01.3 Epicenter: 19.36 N., 155.25 W. Depth: 10 km Magnitude: 3.2 ML Intensity II: Hilo.

9 August (H) Island of Hawaii Origin time: 23 09 33.5 Epicenter: 19.39 N., 155.24 W. Depth: 5 km Magnitude: 3.4 ML Intensity III: Hawaii National Park. Intensity II: Hawaiian Volcano Observatory.

11 August (H) Island of Hawaii Origin time: 05 03 47.5 Epicenter: 19.32 N., 155.22 W. Depth: 10 km Magnitude: 3.5 ML Intensity II: Hilo. Kurtistown. Volcano.

12 August (H) Island of Hawaii Origin time: 02 30 11.0 Epicenter: 19.34N., 155. 19 W. Depth: 9 km Magnitude: 2.7 ML Intensity II: Hawaii National Park.

15 August (H) Island of Hawaii Origin time: 03 01 00.3 Epicenter: 19.36 N., 155.14 W. Depth: 9 km Magnitude: 3.2 ML Intensity II: Volcano.

18 August (H) Island of Hawaii Origin time: 03 25 34.5 Epicenter: 19.41 N., 155.26 W. Depth: 2 km Magnitude: 2.3 ML Intensity II: Volcano.

23 August (H) Island of Hawaii Origin time: 02 26 55.8 Epicenter: 19.38N., 155. 24 W. Depth: 5 km Magnitude: 2.2 ML Intensity II: Hawaii National Park.

C20

Table 2.-Summary of macroseismic data for U.S. earthquakes,

26 August (H) Island of Hawaii

31 August (H) Island of Hawaii

2 September (H) Island of Hawaii

4 September (H) Island of Hawaii

4 September (H) Island of Hawaii

6 September (H) Island of Hawaii

8 September (H) Island of Hawaii

8 September (H) Island of Hawaii

July-September 1976 -Continued

Origin time: 13 19 43.5 Epicenter: 19.36 N., 155.25 W. Depth: 10 km Magnitude: 3.6 ML Intensity III: Volcano. Intensity II: Hilo, Mountain View, Papaikou.

Origin time: 20 41 08.3 Epicenter: 19.39 N., 155.49 W. Depth: 10 km Magnitude: 4.0 ML Intensity III: Hawaiian Volcano Observatory Intensity II: Kona.

Origin time: 20 20 26.7 Epicenter: 19.35 N., 155.05 W. Depth: 8 km Magnitude: 3.5 ML Intensity III: Hilo. Intensity II: Kalapana.

Origin time: 08 03 41.4 Epicenter: 19.48 N., 154.86 W. Depth: 9 km Magnitude: 3.5 ML Intensity III: Pahoa.

Origin time: 23 10 54.1 Epicenter: 19.33N., 155. 27 W. Depth: 10 km Magnitude: 3.9 ML Intensity III: Hawaiian Volcano Observatory, Volcano. Intensity II: Hilo, Honaunau, Keaau, Pahoa.

Origin time: 15 34 15.2 Epicenter: 19.44N., 154.91 W. Depth: 9 km Magnitude: 3.5 ML Intensity III: Glenwood. Intensity II: Hawaii National Park.

Origin time: 08 01 16.2 Epicenter: 19.37 N., 155.08 W. Depth: 8 km Magnitude: 3."5 ML Intensity III: Hilo, Kurtistown. Intensity II: Hawaii National Park.

Origin time: 14 01 55.4 Epicenter: 19.31 N., 155.35 W. Depth: 9 km Magnitude: 3.2 ML Intensity II: Glenwood, Hilo.

10 September (H) Island of Hawaii Origin time: 06 46 22.2 Epicenter: 19.39 N., 155.07 W. Depth: 8 km Magnitude: 2.5 ML Intensity II: Mountain View.

11 September (H) Island of Hawaii Origin time: 15 04 30.4 Epicenter: 19.37N., 155. 07 W. Depth: 8 km Magnitude: 3.6 ML Intensity III: Hilo. Intensity II: Keaau.

12 September (H) Island of Hawaii Origin time: 23 21 43.3 Epicenter: 19.43 N. , 154.97 W. Depth: 5 km Magnitude: 2.8 ML Intensity II: Pahoa.

21 September (H) Island of Hawaii Origin time: 19 35 49.7 Epicenter: 19.35 N., 155.11 W. Depth: 9 km Magnitude: 3.2 IIL Intensity II: Hilo.

28 September (H) Island of Hawaii Origin time: 19 14 53.3 Epicenter: 19.33N., 155. 22 W. Depth: 10 km Magnitude: 3. 7 ML Intensity III: Hawaiian Volcano Observatory,

Intensity II: Honaunau, Honokaa, Kapapala

29 September (H) Island of Hawaii Origin time: 22 58 03.9 Epicenter: 19.34 N., 155.09 W. Depth: 9 km Magnitude: 3.3 ML Intensity III: Hilo.

26 July (G) Western Idaho Origin time: 10 45 28.2 Epicenter: 45.02 N., 114.18 W. Depth: 10 km Magnitude: 4.3 mb, 4.4 ML Intensity V: Cobalt, North Fork, Tendoy. Intensity IV: Carmen, Ellis, Salmon, Shoup,

July-September 19 76 -Continued

Hilo.

Ranch, Mountain View, Naniwale, Papaikou, Pepeekeo.

Williams Lake (oress reoort).

C21

Table 2.-Summary of macroseismic data for U.S. earthquakes,

28 July (G) Western Montana

14 August (G) Western Nevada

14 August (G) Western Nevada

14 August (G) Western Nevada

26 August (A) Southern Nevada

20 September Southern Oklahoma

July-September 7976-Continued

Origin time: 05 06 16.9 Epicenter: 47.55 N., 112.73 W. Depth: 5 km Magnitude: 3.5 ML(D), 3.5 ML Intensity IV: Augusta.

Origin time: 07 50 44.9 Epicenter: 39.48N., 119. 62 W. Depth: 7 km Magnitude: 2.2 ML Intensity II: Steamboat (University of Nevada, oral commun., 1976).

Origin time: 07 58 32.4 Epicenter: 39.45 N. , 119.54 W. Depth: 4 km Magnitude: 3.1 ML(B) Intensity II: Steamboat (University of Nevada, oral commun., 1976).

Origin time: 08 08 03.1 Epicenter: 39.43N., 119. 64 W. Depth: 6 km Magnitude: 2.2 11L Intensity II: Steamboat (University of Nevada, oral commun., 1976).

Origin time: 14 30 00.2 Epicenter: 37.13N., 116.08 W. Depth: 0 km Magnitude: 5.3 mb, 4.2 MS, 5.1 ML(B)

Nevada Test Site explosion "Banon" at 37°07'

30.03" N., 116°04' 55.19" W. , surface elevation 1,302 m.

Origin time: 09 40 Epicenter: Not located. Depth: None computed. Magnitude: 2.2 ML(T) Intensity II: Wilson. Montana

Table 2.-Summary of macroseismic data for U.S. earthquakes,

13 September (G) Virginia-North Carolina border Origin time: 18 54 37.1 Epicenter: 36.60 N., 80.81 W. Depth: 5 km Magnitude: 3.3 mbLg(V)

An area around the epicenter having a radius

Intensity VI:

July-September 7976-Continued

of 150 km was canvassed by the U.S. Geological Survey and 356 questionnaires were mailed. In addition, data were also provided by G. A. Bollinger, Virginia Polytechnic Institute and State University, at Blacksburg, and by Law Engineering Testing Company, Marietta, Georgia. These data were evaluated by the U.S. Geological Survey and the combined results are listed below. The quake was felt over an area of approximately 17,500 sq km, as shown in figure 8.

North Carolina Toast (cracked masonry, cracked plaster; guards on fluorescent light fixtures and metal sorting cases in post office rattled violently. Loud noises resembling explosions were heard.), Mt. Airy (bricks dislodged from chimney).

WEST

Table 2.-Summary of macroseismic data for U.S. earthquakes,

Intensity V:

Intensity IV;

July-September 19 76- Continued

North Carolina Advance, Dobson, East Bend, Ennice, Glade Valley, Pilot Mountain, Piney Creek, Rural Hall, Siloam, Sparta, State Road, Thurmond, White Plains. Virginia Cana, Fancy Gap, Fries, Galax, Lambsburg.

North Carolina Ararat, Belle Island (two shocks felt several seconds apart at Currituck Sound), Boonville, Borum Springs, Concord (north-south motion reported), Elkin (loud sound like an explosion rattled windows and doors; water in bathtub rippled), Grandy (three shocks felt), Hamptonville, Harmony, Hillsville, Jonesville, Kitty Hawk (6.3 km north on Currituck Sound; two tremors noted, each lasting several seconds and separated by several seconds, described as relatively high frequency vibration that did not vary in intensity from beginning to end, but began and ceased abruptly.), Knotts Island (rattling of windows and doors, lasting about 10 seconds), Landis, Lewisville, Lowgap, Maple (in Currituck County5 three shocks felt in approximately 5 minutes, two

Table 2.-Summary of macroseismic data for U.S. earthquakes,

Intensity III;

48C Table 2. Summary of macroseismic data for U.S. earthquakes, July-September /976-Continued

Virg inia Cont inued Virginia Cont inued

close together), Millers Creek, Pilot Mountain, Powells Point (on Albemarle Sound), Roaring River, Ronda, Salisbury Intensity II: (southern Rowan County), Scottville, Sparta, Statesville, Union Grove, Westfield, Whitehead, Wilbar, Woodleaf. Virginia Austinville, Claudville, Cripple Creek, Independence, Mouth of Wilson, Stuart, Woodlawn. West Virginia Anawalt.

North Carolina Blowing Rock, Boomer, Denton, Kannapolis, Moyock (lasted longer

C23 July-September 19 76 -Continued

than 10 seconds), Needmore, Traphill. Virginia Ararat, Fancy Gap, Roanoke, Trout Dale.

North Carolina Charlotte, Longview, Manteo (two shocks felt), Mt. Pleasant. South Carolina Columbia (felt on upper floors of an eight-story building telephone report), Greenville (telephone report).

Virginia Indian Valley, Laurel Fork, Marion.

7 Felt at intensity 7

Table 2.-Summary of macroseismic data for U.S. earthquakes, Table 2.-Summary of macroseismic data for U.S. earthquakes.

2 September (W) Northwestern Washington Origin time: 13 36 11.0 Epicenter: 48.20N., 122.76 W. Depth: 24 km Magnitude: 4.3 mb(G), 4.0 I-IL(G)

This earthquake was widely felt in the

Intensity V; Bremerton, Carlsburg,

Intensity IV; Blakely Island, Bothell,

Intensity III; Bow, Keyport, Mt. Vernon

Intensity II; Capitol Hill.

8 September (W) Northwestern Washington Origin time: 08 21 01.6 Epicenter: 47.38N., 123.08 W. Depth: 48 km Magnitude: 4.6 mb(G), 3.9 MS(G), 4.8 ML(G)

An area around the epicenter having a radius

Intensity VI; Tacoma (broken glassware,

Intensity V; Allyn, Aloha, Anderson Island,

July-September 1976 July-September 1976

following Washington counties: Clallam, Island, Jefferson, King, Kitsap, San Juan, Skagit, Snohomish, and Whatcoin, as well as in Vancouver and Victoria in British Columbia (press report). An area around the epicenter having a radius of 125 km was canvassed by the USGS and 244 questionnaires were mailed. This quake was felt throughout the Puget Sound area, as shown in figure 9.

3 September (G) Northeastern Wyoming Coupeville, Everett, Greenbank, Hadlock, Joyce, La Connor, Lopezi, Lummi Island, Oak Harbor, Olga, Orcas, Port Angeles, Port Townsend, Quilcene, Seattle, Shaw Island, Stanwood, Waldron, Whidbey Island.

Brinnon, Chimacum, Clearlake, Eastsound, Ferndale, Freeland, Friday Harbor, Gardiner, Lyman, Lynnwood, Magnolia, Port Ludlow, Sequim, Skykomish.

(press report).

of 150 km was canvassed and 336 questionnaires were mailed. The quake was felt throughout the Puget Sound area, as shown in figure 10.

other slight damage, many awakened and frightened press report).

Auburn, Belfair, Burley, Carnation, Dockton, East Olympia, Fox Island, Grapeview, Lilliwaup, Longbranch, Lopez, Lyman, Manchester, Matlock, McMillin, Mercer Island (press report), Milton, Mineral, Nordland, Oakville, Olga, Olympia, Pacific, Puyallup, Redondo, Renton, Rochester, Rolling Bay, Seattle, Shaw Island, Shelton, South Colby, Startup, Tahuya, Tracyton, Union, Vashon, Victor (press repo'rt), West Seattle (press report).

C24

Intensity IV; Ashford, Bremerton, Carbonado, Fort Lewis, Hoodsport, Indianola, Joyce, Lakebay, Lynnwood, Malone, McCleary, Normandy Park (press report), Randle, Seattle-Tacoma Airport (control-tower personnel estimated tower swayed 3 m), Sumner. Intensity III; Duvall, Seabeck. Intensity II; Auburn, Suquamish.

Origin time: 04 18 16.2 Epicenter: 44.04 N., 106.15 W. Depth: 10 km Magnitude: 4.8 mb, 4.2 ML Intensity V; Kaycee (small objects and light furniture moved, building creaked, seve ral f r igh tened).

o Port Angeles^1 ° \ -vT£&

ACKNOWLEDGMENTS VIRGINIA: G. A. Bollinger, Department of

Listed below are the collaborators who Polytechnic Institute and State furnished data to the National Earthquake University, Blacksburg. Information Service for use in this circular: WASHINGTON: Robert S. Crosson, Geophysics

ALASKA: Staff of NOAA, Alaska Tsunami Warning

CANADA: Gary Rogers, Victoria Geophysical processing the intensity data and drafting the

CALIFORNIA: Clarence R. Alien, Seismological computerized manuscript.

HAWAII: Robert Y. Koyanagi, U.S. Geological Fuis, G. S., Friedman, M. E., and Hileman, J. A.,

MISSOURI: Otto Nuttli, Department of Geology 77-181, 107 p.

NEW YORK: Lynn R. Sykes and Yash P. Aggarwal, Geofisica, v. 9, no. 1, p. 1-15.

OKLAHOMA: James E. Lawson, Jr., University of 5 > P' 876 ~ 885 '

UTAH: Department of Geological and Wood, H. 0., and Neumann, F., 1931, Modified Center, Palmer. Acknowledgment is also given to B. B. Poppe for

Observatory. isoseismal maps, and to Paula Smith for doing the

Laboratory, California Institute of Technology, Pasadena. REFERENCES CITED Bruce A. Bolt, Seismograph Station, University of , . , n , f , California Berkeley. Bath ' Markus » 1966 » Earthquake energy and ' magnitude, in Physics and chemistry of the Gary S. Fuis, U.S. Geological Earth> volume 7: Oxford and New York, Survey, Pasadena. Pergamon Press, p. 115-165.

Survey, Hawaiian Volcano 1977, Preliminary catalog of earthquakes in Observatory, Hawaii National southern California, July 1974-September Park. 1976, U.S. Geological Survey Open-File Report

and Geophysics, St. Louis Gutenberg, B. and Richter, C. F., 1956, Magnitude University, St. Louis. and energy of earthquakes: Annali di

Lamont-Doherty Geological Nuttli, 0. W., 1973, Seismic wave attenuation and Observatory, Columbia magnitude relations for eastern North University, Palisades. America: Jour. Geophys. Research, v. 78, no.

Oklahoma, Earth Sciences Richter, C. F., 1958, Elementary seismology: San Observatory, Leonard. Francisco, Calif., W. H. Freeman and Co. f< Inc., 768 p.

Geophysical Sciences, University Mercalli Intensity Scale of 1931; Seismol.

of Utah, Salt Lake City. Soc. America Bull., v. 21, no. 4, p. 277-283. Geological Sciences, Virginia

Program, University of Washington, Seattle.

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