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**Tsunamis****Earthquakes****Volcanoes**

| Earthquake Intensity Database              1638 - 1985Download Database (MS Excel format;                15MB)                                                   |
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| - Introduction
- Description of Database
- Definition of Variables
- History of Earthquake Intensity Scales
- Collecting Data on Earthquake Intensity
- References | Earthquake intensities are numerical values assigned to the effects of earthquakes               on people and their works, and on the natural environment.  Intensities are evaluated               using the Modified Mercalli Intensity Scale of 1931, which contains levels of effects               ranging from intensity I, barely perceptible, to intensity XII, total damage.

Although the development of seismological instruments and instrumental              techniques the past 80 years has been impressive, earthquake intensity              remains among the most acceptable criteria on which to base earthquake              risk factors and to project future seismic activity (Brazee, 1976).              This, in part, is due to the extensive availability of earthquake              intensity data (from the mid-1600s) compared to the availability of              earthquake instrumental data (from about 1897).

Earthquake intensity information is a unique and valuable data source              for the research seismologist, the structural engineer, the actuary, and              the earth science instructor.  Although published information on              earthquake effects has been available for many years (see "References"),              compiling comprehensive lists of earthquakes and the intensities              that were experienced at nearby cities still required much time and              effort by the researcher.

In the early 1960s, however, preparing lists of historical earthquakes              became less laborious and time consuming after the U.S. Coast and              Geodetic Survey compiled a computerized data file of worldwide              earthquakes.  The file not only contained epicenters of earthquakes but              also held other valuable information on each event, including the              maximum reported intensity.  The new file still had limitations,              however, because the names of cities experiencing the earthquakes and              the intensities at these cities were not included in the data base.  The              next logical step, therefore, was to compile another file--an              Earthquake Intensity File--that not only would include instrumental              earthquake data, but also would contain the important ancillary data              on earthquake effects.
Description of Database            The Earthquake Intensity File contains more than 157,000 reports on over            20,000 earthquakes that affected the United States from 1638 through 1985.            The principal data included for each earthquake in the file are the names            and geographic coordinates of cities (or localities) that have reported            effects from earthquakes (hereafter called "reporting cities") and the            intensities assigned to those effects.  Each intensity has been assigned            using the Modified Mercalli Intensity Scale of 1931 (Wood and Neumann, 1931).            Other information given for each earthquake includes:  distance of each            reporting city from the epicenter of the earthquake; number of hours to            subtract from Universal Time (UT) to obtain origin time in local standard            time; reference (authority) codes for reporting cities and intensity values;            and state codes.  In addition, the date, origin time, epicenter, magnitude,            and depth (where available) are given for all earthquakes.             Although the Earthquake Intensity File represents an important contribution            to seismology research, it has several limitations that should be mentioned:            - About 25 percent of the 2,500 earthquakes reported from 1638-1928                and 10 percent of the 18,500 events from 1928-80 do not have instrumental                epicenters; this omission is mainly due to the fact that seismological                instruments were not developed until the late 1800s, and further that the                instruments were not widely distributed for many years later.
- Several of the reporting cities (or localities) listed in the file have not                been assigned geographic coordinates.
- The file contains data primarily for those earthquakes that have epicenters                in the United States, nearby U.S. territories, and areas of Canada and Mexico                that border the United States.  Data for a few events in the Philippines                (from the late 1930s through 1941) are also included.
Definition of Variables- Year Mo Da Hr Mn Sec
- The Date and Time are listed in Universal Coordinated Time and are                Year, Month (Mo), Day (Da), Hour (Hr), Minute (Mn), Second (Sec)
- UTC Conv
- Number of hours to subtract from the Date and Time given in Universal                Coordinated Time to get local standard time for the epicenter.  In                general:
-    - 4 = 60 degree meridian (Atlantic Standard Time)
  - 5 = 75 degree meridian (Eastern Standard Time)
  - 6 = 90 degree meridian (Central Standard Time)
  - 7 = 105 degree meridian (Mountain Standard Time)
  - 8 = 120 degree meridian (Pacific Standard Time)
  - 9 = 135 degree meridian (Alaska Standard Time)
  - 10 = 150 degree meridian (Hawaii-Aleutian Standard Time) 
 Use care when converting Universal Coordinated Time to local standard time.              It is uncertain how some of the conversion factors in this database were              determined--for example, whether Daylight Saving Time or Standard Time was              used.  Many, but not all, areas represented in this database have observed              Daylight Saving Time during the summer.               Prior to 1966, states and communities that observed Daylight Saving used              whatever beginning and ending dates they chose.  The Uniform Time Act              of 1966 provided that any area that observes Daylight Saving Time must              begin and end on specified federal dates.               The Uniform Time Act of 1966, P.L. 89-387, section 4(c), also established              four time zones in Alaska:              - Pacific Standard Time (120th meridian--southeastern Alaska--8 hours behind UTC)
- Yukon Standard Time (135th meridian--Yakutat--9 hours behind UTC)
- Alaska-Hawaii Standard Time (150th meridian--most of Alaska, from                   west of Yakutat to just east of Cold Bay, and northward--10 hours behind UTC)
- Bering Standard Time (165th meridian--westward from just east of Cold Bay, at the western                   end of the Alaska Peninsula--11 hours behind UTC)
              On October 30, 1983, the number of time zones in Alaska was reduced from four to two,               which placed 90 percent of Alaska on the same time, just one hour behind the U.S. West               Coast; the boundary between the two zones is just west of Umnak Island in the Aleutian               chain:              - Alaska Standard Time (9 hours behind UTC)
- Hawaii-Aleutian Standard Time (10 hours behind UTC)
- U/G
- Unpublished or grouped intensity
- U = Intensity (MMI) assigned that was not listed in the source document. 
- G = Intensity grouped I-III in the source document was reassigned intensity III. 
- EQ Lat / EQ Long
-  This is the geographic latitude and longitude of the epicenter expressed as decimal                 numbers. The units are degrees. The latitude range is +4.0 to +69.0, where "+" designates                 North latitude (there are no South latitudes in the database). The longitude range is                 -179.0 to +180.0, where "-" designates West longitude and "+" designates East longitude.                 Most of the epicenters are West longitude (from -56 to -179), but a few epicenters in the                 Philippines and Aleutian Islands are East longitude (from +120 to +180). 
- Mag
-  These are magnitudes as listed in  **United States Earthquakes** ,  **Earthquake                 History of the United States**  (either mb, MS, or ML), or the equivalent derived from                 intensities for pre-instrumental events. The magnitude is a measure of seismic energy.  The                 magnitude scale is logarithmic. An increase of one in magnitude represents a tenfold increase                 in the recorded wave amplitude. However, the energy release associated with an increase of one                 in magnitude is not tenfold, but thirtyfold. For example, approximately 900 times more energy                 is released in an earthquake of magnitude 7 than in an earthquake of magnitude 5. Each increase                 in magnitude of one unit is equivalent to an increase of seismic energy of about 1,600,000,000,000 ergs. 
- Depth (km)
-  Hypocentral Depth (positive downward) in kilometers from the surface. 
- Epi Dis
-  Epicentral Distance in km that the reporting city (or locality) is located from the epicenter of the earthquake. 
- City Lat / City Long
-  This is the geographic latitude and longitude of the city (or locality) where the Modified Mercalli                 Intensity was observed, expressed as decimal numbers. The units are degrees. The latitude range is +6.0 to +72.0,                 where "+" designates North latitude (there are no South latitudes in the database). The longitude range is                 -177.0 to +180.0, where "-" designates West longitude and "+" designates East longitude. Most of the reporting                 cities (or localities) are West longitude (from -29 to -177), but a few reporting cities (or localities) in                 the Philippines and Aleutian Islands are East longitude (from +119 to +180). 
- MMI
- Modified Mercalli Scale Intensity  (MMI)                is given in Roman Numerals. Values range from I to XII.                (Roman Numerals were converted to numbers in the digital database.                Values range from 1 to 12.) Macroseismic information is compiled from                various sources including newspaper articles, foreign broadcasts, U.S.                Geological Survey Earthquake reports and seismological station reports.
- State Code
-  Numerical identifier for state, province, or country in which the earthquake                was reported (felt) by residents:                 01 Alabama          02 Alaska           03 Arizona04 Arkansas         05 California       07 Colorado08 Connecticut      09 Delaware         10 District of Columbia11 Florida          12 Georgia          14 Hawaii15 Idaho            16 Illinois         17 Indiana18 Iowa             19 Kansas           20 Kentucky21 Louisiana        22 Maine            23 Maryland24 Massachusetts    25 Michigan         26 Minnesota27 Mississippi      28 Missouri         29 Montana30 Nebraska         31 Nevada           32 New Hampshire33 New Jersey       34 New Mexico       35 New York36 North Carolina   37 North Dakota     38 Ohio39 Oklahoma         40 Oregon           41 Pennsylvania42 Puerto Rico      43 Rhode Island     45 South Carolina46 South Dakota     47 Tennessee        48 Texas49 Utah             50 Vermont          51 Virginia52 Virgin Islands   54 Washington       55 West Virginia56 Wisconsin        57 Wyoming          58 West Indies74 Panama           75 Philippine Is.   80 Mexico81 Baja California  90 Canada           91 Alberta92 Manitoba         93 Saskatchewan     94 British Columbia95 Ontario          96 New Brunswick    97 Quebec98 Nova Scotia      99 Yukon Territory 
- City Name
-  City (or locality) in which the earthquake was reported (felt) by residents. 
- Data Source
-  This is a code referring to the source of one or more of the reported parameters (e.g., epicenter, city and intensity).
A = Source unknown; 1925 earthquake in Boston area (reports not listed in source H).B = Report by Bollinger and Stover, 1976.C = Quarterly Seismological Reports, 1925-27.D = Source unknown; 1937-1977 earthquakes in Hawaii, California, and eastern U.S.H = Earthquake History of the United States (Coffman and others, 1982).K = Report by Carnegie Institution, 1908, 1910.M = Source unknown; 1899-1912 earthquakes in Alaska.N = Report by Nuttli, 1973.Q = Abstracts of Earthquake Reports for the United States, 1933-70.S = Unpublished report by Nina Scott, 1965.T = Source unknown; 1872-1904 earthquakes along U.S. west coast.U = United States Earthquakes, 1928-85.  W = Monthly Weather Service Seismological Reports, 1914-24.  History of Earthquake Intensity Scales            Although the history of the development of earthquake intensity scales            is long and interesting, only a brief summary will be presented here.            Poarid, an Italian, made the first known attempt to classify earthquakes            by intensity in 1627; he used a scale of four levels of intensity to            describe effects of earthquakes experienced at different towns.            Although many additional attempts were made in the 18th and 19th            centuries to develop comprehensive scales for measuring earthquake            intensity, none was more widely used than that formulated in 1873 by            M. S. de Rossi of Italy and F. A. Forel of Switzerland.  But this scale            also had severe limitations, and therefore was superseded in the early            1900s by Mercalli's revised intensity scale; it contained 12 levels of            intensity.             In 1931, a modified version of Mercalli's scale was published by H. O.            Wood and Frank Neumann.  Known as the Modified Mercalli Intensity            Scale of 1931, it has become the standard used by the United States            engineering seismology community, which includes the National            Geophysical Data Center and the U.S. Geological Survey.            An interpretation of the values is listed in Table 1.Table 1.--Modified Mercalli Intensity Scale of 1931I. Not felt except by a very few under especially              favorable circumstances. II. Felt only by a few persons at rest, especially              on upper floors of buildings.  Delicately suspended objects may swing. III. Felt quite noticeably indoors, especially on              upper floors of buildings, but many people do not recognize it as an              earthquake. Standing motor cars may rock slightly. Vibration like passing              truck. Duration estimated. IV. During the day felt indoors by many, outdoors by              few.  At night some awakened. Dishes, windows, and doors disturbed; walls make              creaking sound.  Sensation like heavy truck striking building.  Standing              motorcars rock noticeably. V. Felt by nearly everyone; many awakened. Some              dishes, windows, etc., broken; a few instances of cracked plaster; unstable              objects overturned. Disturbance of trees, poles, and other tall objects              sometimes noticed. Pendulum clocks may stop. VI. Felt by all; many frightened and run outdoors.              Some heavy furniture moved; a few instances of fallen plaster or damaged              chimneys. Damage slight. VII. Everybody runs outdoors.  Damage negligible in              buildings of good design and construction slight to moderate in well built              ordinary structures; considerable in poorly built or badly designed structures.              Some chimneys broken.  Noticed by persons driving motor cars. VIII. Damage slight in specially designed structures;              considerable in ordinary substantial buildings, with partial collapse; great              in poorly built structures.  Panel walls thrown out of frame structures. Fall              of chimneys, factory stacks, columns, monuments, walls. Heavy furniture              overturned. Sand and mud ejected in small amounts. Changes in well water.              Persons driving motor cars disturbed. IX. Damage considerable in specially designed              structures; well-designed frame structures thrown out of plumb; great in              substantial buildings, with partial collapse. Buildings shifted off foundations.              Ground cracked conspicuously.  Underground pipes broken. X. Some well-built wooden structures destroyed; most              masonry and frame structures destroyed with foundations; ground badly cracked.              Rails bent.  Landslides considerable from river banks and steep slopes.              Shifted sand and mud.  Water splashed over banks. XI. Few, if any (masonry), structures remain standing.              Bridges destroyed.  Broad fissures in ground. Underground pipelines completely              out of service.  Earth slumps and land slips in soft ground.  Rails bent greatly. XII. Damage total. Waves seen on ground surfaces. Lines              of sight and level distorted. Objects thrown upward into the air. Reference: Harry O. Wood and Frank Neumann, in Bulletin of the          Seismological Society of America, Vol. 21, No. 4, December 1931.          es Geophysicae, 4B, (6), Paris, France, 1986, pp. 679-702.            Comparison of Modified Mercalli (MM) and Other Intensity Scales            ModifiedMercalli    Rossi-Forel    Japanese    European   I             I            0           I   II            I-II         I           II   III           III          II          III   IV            IV-V         II-III      IV   V             V-VI         III         V   VI            VI-VII       IV          VI   VII           VIII-        IV-V        VII   VIII          VIII+ to     V           VIII                 IX-   IX            IX+          V-VI        IX   X             X            VI          X   XI            -----        VII         XI   XII           -----        -----       XIICollecting Data on Earthquake Intensity
The U.S. Geological Survey (USGS) is the Federal agency responsible for            collecting earthquake intensity data.  The USGS carries out this responsibility            using a questionnaire called "Earthquake Report," and also sends field            investigators to the scene of destructive earthquakes to analyze the resulting            damage.  Different versions of the questionnaire have been used since the            mid-1920s by several groups who were responsible for collecting intensity data.            The present questionnaire contains pertinent questions about earthquake effects            that enable a seismologist to evaluate the intensity of the earthquake in all            parts of the shaken area; it also is designed specifically for computer            processing.

            In the past, the USGS sent questionnaires immediately after each U.S. earthquake            to postmasters, National Weather Service offices, military installations, and            others, requesting that they report all effects of the earthquake in their area.            If the earthquake was damaging, expert observers travelled to the field to            investigate and photograph the damage incurred.  This data-collection program            was supplemented by newspaper accounts of earthquake effects, published            scientific reports, and reports provided by seismology collaborators.

            After the completed earthquake questionnaires were returned to USGS, a            seismologist analyzed each report and assigned intensities on the basis of the            effects at each town; intensity (or isoseismal) maps were then constructed for            earthquakes felt over large areas.  Descriptions and maps of these events were            published annually in the United States Earthquakes series, and a summary of            the stronger earthquakes (MM intensity >= V) was published periodically in            Earthquake History of the United States.

            The USGS now only canvasses selected earthquakes. If you want to report an             earthquake, use the National Earthquake Information Center's Did You Feel it? page.
References
The main sources of data used in compiling the Earthquake Intensity Database

***Earthquake History of the United  States***            This publication is a summary of all earthquakes (intensity V and above)            that have occurred in the United States and its territories from earliest            recorded history (about 1638 in the New England region) through 1980. The            1982 edition of this publication (Coffman and others, 1982) contains revised            epicenters and intensities for several earthquakes.  This source, therefore,            is the authority for epicenters of significant earthquakes in the file and            also for most intensities of MM intensity >= V.  In addition, pages xi-xii            of "Earthquake History" contain several addenda and corrigenda, which have            been used to update information in the Intensity File.

***United States Earthquakes***            Much of the intensity data in the Earthquake Intensity Database for 1928-85            were taken from this annual report.  Its publication in 1928 began a continuing            program of collecting comprehensive effect reports on all earthquakes in the            United States and its territories.  This publication not only contains brief            descriptions of all earthquakes that were felt or damaging, but also includes            MM intensities for most of the cities (or localities) in which the tremors were            observed.  For earthquakes in 1928-31, however, published intensities were            assigned using the Rossi-Forel (RF) intensity scale.  Where included in the            Intensity File, these intensities are converted to values on the MM scale. In            addition, some descriptions of earthquake effects in United States Earthquakes            were not assigned an intensity because the effect information was insufficiently            detailed (e.g., "slight," "feeble," "felt").  To make the computerized file as            complete as possible, NCEI assigned an intensity of II to earthquake reports            that had only the slightest of details, and an intensity of III to earthquake            reports that were grouped as intensity I-III. 

***Quarterly Seismological Report***            This publication, which was published by the U.S. Coast and Geodetic            Survey, was a source of information on reporting cities and intensities            for the years 1925-27.  All Rossi-Forel intensities assigned to            earthquake reports during this period have been converted to the MM            Intensity Scale.  Where omitted, intensities have been assigned            according to the method described in the preceding paragraph. 

***Abstracts of Earthquake Reports for the United States***            This quarterly publication includes all the effect data collected for            earthquakes in the United States and its territories during the 1933-70 period.            Because the quarterly "Abstracts" report contains only preliminary earthquake            data, information in United States Earthquakes annual reports and in Earthquake            History of the United States is preferred, for they contain additional            reporting cities and revised intensity information.

***Monthly Weather Service Seismological Reports***            These reports represent a main source for information on earthquake            effects in the United States and nearby territories for December 1914            through June 1924. As in other pre-1931 publications all intensities            were assigned according to the Rossi-Forel scale; however, minimal            reported effects (e.g., slightly felt) were not assigned intensities.            NCEI, therefore, has assigned intensities to all effects and, in            addition, has converted Rossi-Forel intensities to the MM scale.
Bibliography- Bollinger, G.A. and Carl W. Stover, 1976:  *List of Intensities for the                1886 Charleston, South Carolina, Earthquake* , U.S. Geological Survey                Open-File Report 76-66, 31 p.
- Brazee, Rutlage J., August 1976:  *Final Report: An Analysis of Earthquake                Intensities with Respect to Attenuation, Magnitude, and Rate of                Recurrence*  (Revised Edition), NOAA Tech. Memorandum EDS NGSDC-2,                NOAA/National Geophysical Data Center, Boulder, Colorado, 53 p. (plus                appendices).
- Carnegie Institution of Washington, vols. 1-2, 1908, 1910:  *California                Earthquake of April 18, 1906, Report of the State Earthquake                Investigation Commission* , v.1 (by Andrew C. Lawson); v. 2 (by Harry F.                Reid), Washington, D.C., 623 p. (plus Atlas).
- Coffman, Jerry L., Carl A. von Hake, and Carl W. Stover, 1982:  *Earthquake History of the United States* , Publication 41-1, Revised                Edition (with Supplement Through 1980), National Oceanic and Atmospheric                Administration and U.S. Geological Survey, Boulder, Colorado, 258 p.
- Dutton, Clarence E., 1889: "The Charleston Earthquake of August 31,                1886,"  *Ninth Annual Report, 1887-88* , U.S. Geological Survey, Washington                D.C., p. 203-528.
- Meyers, Herbert, April 1976:  *A Historical Summary of Earthquake                Epicenters in and Near Alaska* , NOAA Tech. Memorandum EDS NGDC-1,                NOAA/National Geophysical Data Center, Boulder, Colorado, 57 p. (plus                appendices).
- Meyers, Herbert and Carl A. von Hake, 1976:  *Earthquake Data File                Summary* , Key to Geophysical Records Documentation No. 5, NOAA/National                Geophysical Data Center, Boulder, Colorado, 32 p. (plus appendices).
- Meyers, Herbert, R.J. Brazee, J.L. Coffman, and S.R. Lessig, 1976:  *An                Analysis of Earthquake Intensities and Recurrence Rates in and Near                Alaska* , NOAA Technical Memorandum EDS NGSDC-3, NOAA/National Geophysical                Data Center, Boulder, Colorado, 101 p.
- Murphy, Leonard M. (Scientific Coordinator), 1973:  *San Fernando,                California, Earthquake of February 9, 1971* , vols. 1-3,                NOAA/Environmental Research Laboratories, Washington D.C.
- Nuttli, Otto W., 1973: "The Mississippi Valley Earthquakes of 1811 and                1812; Intensities, Ground Motion, and Magnitudes,"  *Bulletin of the                Seismological Society of America* , v. 63, No.1, p. 227-248.
- Scott, Nina, 1965: List of Modified Mercalli intensities for the April                8, 1906, San Francisco, California, Earthquake, Prepared under contract for                U.S. Geological Survey, unpublished manuscript.
- Tarr, Ralph S. and Lawrence Martin, 1912: "The Earthquakes at Yakutat                Bay, Alaska, in September 1899,"  *U.S Geological Survey Professional                Paper 69* , U.S. Department of the Interior, Geological Survey, Washington                D.C., 135 p.
- U.S. Department of Commerce, Coast and Geodetic Survey,  *Quarterly                Seismological Report, 1925-27* , Washington D.C.
- U.S. Department of Commerce, Environmental Science Services                Administration, vols. 1-3, 1966, 1967, 1969:  *The Prince William Sound,                Alaska, Earthquake of 1964 and Aftershocks* , Publication 10-3 (in three                volumes), Washington, D.C.
- U.S. Department of Commerce, National Oceanic and Atmospheric                Administration (and predecessor agencies),  *Abstracts of Earthquake                Reports for the United States* , quarterly issues 1933-70. (Earlier title:                Abstracts of Earthquake Reports for the Pacific Coast and the Western                Mountain Region).
- U.S. Department of Commerce, National Weather Service,  *Monthly Weather                Review* , December 1914-June 1924 (Seismological reports are usually                described in the issues for the month in which the earthquakes                occurred), Washington D.C.
- U.S. Geological Survey,  *United States Earthquakes* , published                annually by: Coast and Geodetic Survey from 1928-68; National Oceanic                and Atmospheric Administration (NOAA) from 1969-72; NOAA/U.S. Geological                Survey from 1973-80; and U.S. Geological Survey from 1981-1986.
- Wood, Harry O. and Frank Neumann, Dec. 1931: "Modified Mercalli                Intensity Scale of 1931,"  *Bulletin of the Seismological Society of                America* , v. 21, No. 4, p. 277-283.
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