United States Earthquakes, 1978 - USGS

ISO' 159 157 158 o 154 J OAHU KAUAI 21 H MOLOKAI LANAI Gp MAUI *4* KAH()OLAWE 20 EXPLAhJATION Magnit jde 5.0 0 50 k m * V o JS,& HAWAII \j* \ NX O "/flh o preparing local and regional seismic histories for engineers, actuaries, and other scientists and answering direct inquiries from the public on all aspects of historical earthquakes. Additional services and products include publishing annual earthquake summaries and revised historical earthquake reports; and making available copies of seismograms, accelerograms, displacement meter records, digitized strong-motion seismograms, and epicenter lists in several formats. Many of these products and services are based on seismic records or other data that have originated with USGS recording networks or with USGS data-reduction facilities. Information concerning services and products of NGSDC may be obtained from the National Geophysical and Solar-Terrestrial Data Center, NOAA/EDIS, Boulder, CO 80303. MAGNITUDE AND INTENSITY RATINGS FIGURE 3. summary of earthquake epicenters in Hawaii for 1978. The selection of intensity or isoseismal maps shown in the Earthquake Descriptions is governed largely by the size of the area affected. This means that sharp, localized shocks of intensity VI (which occur mostly in California) may not be represented by these maps, whereas other earthquakes of intensity V and VI (which occur largely in the Eastern and Central States) often will be illustrated because of the larger felt areas. Numerals on these computer-plotted maps represent the maximum MM intensities at each town. Isoseismal contours are a generalization of intensity data and are extrapolated to regions that have no observations. The contours do not include each intensity observation. EARTHQUAKE INFORMATION SERVICES The USGS coordinates the collection of all types of earthquake information, with the special objective of correlating instrumentally determined earthquake locations with noninstrumental locations indicated by intensity data. This correlation is achieved through intensive regional investigations of earthquakes by local organizations and the USGS. Primary data are gathered by a canvass of the epicentral area using questionnaire cards. When returned and analyzed, this information is used to map the seismic areas of the country in order to promote public safety through a better understanding of earthquake phenomena. The National Geophysical and SolarTerrestrial Data Center (NGSDC), one of the five major facilities of NOAA's Environmental Data and Information Service, is responsible for data activities in seismology. Its services include Magnitude, a measure of the "size" of an earthquake, is roughly related to the energy release at the focus of an earthquake. Although the magnitude scale has neither "top" nor "bottom" values the highest ever recorded was magnitude 8.9 and the lowest about -3. On this logarithmic scale, a magnitude 6 shallow-focus earthquake represents elastic-wave energy about 30 times greater than that generated by a magnitude 5 earthquake, 900 times greater than that of a magnitude 4 shock, and so forth. Many factors enter into the determination of earthquake magnitude, including earthquake focal depth, frequency content of the sampled energy, and the earthquake radiation pattern. Magnitude values calculated by the USGS are based on the following formulas: MS log (A/T) 1.66 log D 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 vertical 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 j D 160 0 . No depth correction is made for depth less than 50 km, and no MS magnitudes are computed for depths greater 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 .1 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 DX5 . ML log A - log A 0 , as defined by Richter (1958, (3) p. 340),

80 100 45 35 EXPLANATION Intensity I-IV 5 Intensity V 6 Intensity VI 7 Intensity VII Figure 4. Earthquakes plotted by Modified United States for 1978. 155 160 165 170 175 180 175 170 165 Mercalli 160 155 150 Intensity 145 140 135 in 130 the conterminous 125 120 115" 60 55 EXPLANATION 50 50 Intensity I-IV 5 intensity V 6 Intensity VI 0 175 180 175 170' 165 300 km 160 155 150 145 140 Figure 5. Earthquakes plotted by Modified Mercalli Intensity in Alaska for 1978.

160 158 o 154 156 Although the Modified Mercalli Intensity Scale is in many instances inadequate for present-day requirements, the scale has been the guide used by the USGS and NOAA and will continue to be so used until a new scale has been devised and has acceptance in the engineering and seismological communities. Questions concerning the interpretation of historical earthquake intensities should be referred to the USGS. -s KAUAI ,OAHU fc MOLOKAI Z LANAI* L) T ( MAUI A KAl IOOLAWE EXPLA NATION Intens ty I-IV 0 50 k m ( '.r . \f imum intensity, which is given in the text and in table 1. HAWAII . MODIFIED MERCALLI INTENSITY SCALE OF 1931 Adapted from Sieberg's Mercalli-Cancani scale, modified and condensed. I. 18 Figure 6. Earthquakes plotted by Modified Mercalli Intensity in Hawaii for 1978. where A is the maximum trace amplitude in millimeters, written by a Wood-Anderson torsion seismometer, and log A0 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 3.75 0.90(log D) log (A/T) 0.5 D 4 , 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 . III 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. (4) mbLg 3.30 1.66(log D) log(A/T) 4 p 30 0 , as proposed by Nuttli (1973), where A/T is expressed in micrometers per second, calculated from the vertical-component 1second Lg waves, and D is the distance in geocentric degrees. Intensity, as applied to earthquakes, represents a quantity determined from the effects on people, manmade objects, and the Earth's surface (landslides, ground fissures). Intensities are assigned according to the descriptions listed in the Modified Mercalli Intensity Scale of 1931 (Wood and Neumann, 1931). There are 12 discrete steps in the MM scale (see next section). An earthquake in a populated area will have different intensities at different localities, owing to the distance from the epicenter of the earthquake, local geological conditions, structural design of buildings, and the earthquake magnitude. The text of this publication gives the intensity for each city where the earthquake was felt and summaries of the strongest effects reported. Each earthquake is further characterized by its max- Not felt - or, except rarely under 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. 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

negligible in buildings of good design and construction, slight to moderate in wellbuilt 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. 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. VI. VII. 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. 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 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. Frightened all general alarm, all ran 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 VIII. Fright general alarm approaches panic. 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. IX. Panic general. Cracked ground 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 oft 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 pra

10 Photograph of Southern Pacific Transportation Company freight train derailment west of Goleta, Calif. 24 11 Isoseismal map for the southern California earthquake of 13 August 1978. 25 12 Photograph of damage to mobile home near Goleta, Calif. 26 13 Isoseismal map for the Lake Tahoe, Calif, earthquake of 4 September .