Significant United States Earthquakes, 1568-2004

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How should this data set be cited?

   U.S. Geological Survey, 200501, Significant United States Earthquakes, 1568-2004: National Atlas of the United States, Reston, VA.

   Online Links:

   • <http://nationalatlas.gov/atlasftp.html?openChapters=chpgeol#chpgeol>

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: 143

   East_Bounding_Coordinate: -60

   North_Bounding_Coordinate: 65

   South_Bounding_Coordinate: 10

3. What does it look like?

4. Does the data set describe conditions during a particular time period?

   Beginning_Date:

   Ending_Date: 31-Jan-2004

   Currentness_Reference: Ground condition

5. What is the general form of this data set?

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

      Indirect_Spatial_Reference:

      U.S. Department of Commerce, 1987, Codes for the Identification of the States, the District of Columbia and the Outlying Areas of The United States, and Associated Areas (Federal Information Processing Standard 5-2): Washington, DC, National Institute of Standards and Technology.

      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (5351)

   2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000278. Longitudes are given to the nearest 0.000278. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is GRS1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222.
      

7. How does the data set describe geographic features?

   Significant United States Earthquakes (described by Quksigx020.dbf)

   Earthquakes within or near to the United States that caused deaths, property damage, or geological effects, or that were experienced by populations in the epicentral area. These events occurred between 1568 and January 2004. (Source: National Atlas of the United States)

   Shape

   The representation of the entity in the data. (Source: National Atlas of the United States)

   Value	Definition
   Point	0-dimensional element

   Quksigx020

   Internal feature number. (Source: National Atlas of the United States)

   Range of values
   Minimum:	1
   Maximum:	5387

   Quake_id

   Internal feature number. (Source: National Atlas of the United States)

   Range of values
   Minimum:	1
   Maximum:	5390

   Year

   The year when the earthquake occurred. (Source: National Atlas of the United States)

   Range of values
   Minimum:	1568
   Maximum:	2004

   Month

   The month when the earthquake occurred. (Source: National Atlas of the United States)

   Value	Definition
   -9999	The month of the event is unknown.

   Range of values
   Minimum:	1
   Maximum:	12

   Day

   The day when the earthquake occurred. (Source: National Atlas of the United States)

   Value	Definition
   -9999	The day of the event is unknown.

   Range of values
   Minimum:	1
   Maximum:	31

   Hour

   The GMT hour of the day when the earthquake occurred, on a 24-hour clock. (Source: National Atlas of the United States)

   Value	Definition
   -9999	The hour of the event is unknown.

   Range of values
   Minimum:	0
   Maximum:	23

   Minute

   The minute of the hour when the earthquake occurred. (Source: National Atlas of the United States)

   Value	Definition
   -9999	The minute of the event is unknown.

   Range of values
   Minimum:	0
   Maximum:	59

   Second

   The second of the minute when the earthquake occurred. (Source: National Atlas of the United States)

   Value	Definition
   -9999.000	The second of the event is unknown.

   Range of values
   Minimum:	0.010
   Maximum:	59.970

   Location

   The name of the town, city, physical feature, or other describable location near to the earthquake event. (Source: National Atlas of the United States)

   Value	Definition
   <Blank>	No location description is available.

   There is no predefined set of valid location names.

   Longitude

   The longitude of earthquake's epicenter in decimal degrees. (Source: National Atlas of the United States)

   Range of values
   Minimum:	-179.990
   Maximum:	180.000

   Latitude

   The latitude of earthquake's epicenter in decimal degrees. (Source: National Atlas of the United States)

   Range of values
   Minimum:	12.686
   Maximum:	68.689

   Depth_km

   The depth of earthquake's focus in kilometers. A value of 0 may indicate the depth is unknown. (Source: National Atlas of the United States)

   Value	Definition
   -9999	The depth is unknown.

   Range of values
   Minimum:	0
   Maximum:	274

   Mb_gs

   The body wave magnitude of the earthquake as reported by the U.S. Geological Survey. A body wave is a seismic wave that travels through the Earth's inner layers. (Source: National Atlas of the United States)

   Value	Definition
   -9999.000	The body wave magnitude is unknown.

   Range of values
   Minimum:	3.400
   Maximum:	7.000

   Ms_gs

   The surface wave magnitude of the earthquake as reported by the U.S. Geological Survey. A surface wave is a seismic wave that travels along the Earth's surface. (Source: National Atlas of the United States)

   Value	Definition
   -9999.000	The surface wave magnitude is unknown.

   Range of values
   Minimum:	3.100
   Maximum:	8.500

   Other_mag1

   The magnitude of the earthquake as reported by the source identified in Ref1. The type of magnitude is described by the attribute Type1. (Source: National Atlas of the United States)

   Value	Definition
   -9999.000	No additional magnitude measurement is available.

   Range of values
   Minimum:	2.080
   Maximum:	9.240

   Type1

   The type of magnitude recorded in the attribute Other_mag1, as defined by the source identified in Ref1. (Source: National Atlas of the United States)

   Value	Definition
   FA	The magnitude given in Other_mag1 is an estimated body wave magnitude. It is commonly computed from the felt area for earthquakes which occurred before seismic instruments were in general use.
   MD	The magnitude given in Other_mag1 is based on the duration or coda length of the earthquake vibration.
   ML	The magnitude given in Other_mag1 is the local magnitude, which is also known as the original "Richter" magnitude.
   MW	The magnitude given in Other_mag1 is the moment magnitude. It is the measure of total energy released by an earthquake.
   Mn	The magnitude given in Other_mag1 is the local or regional magnitude. It is the body wave magnitude using the Lg wave.
   Ms	The magnitude given in Other_mag1 is the surface wave magnitude. A surface wave is a seismic wave that travels along the Earth's surface.
   Mw	The magnitude given in Other_mag1 is the moment magnitude.
   UK	The magnitude type for the magnitude given in Other_mag1 is unknown.
   mb	The magnitude given in Other_mag1 is the body wave magnitude. A body wave is a seismic wave that travels through the Earth's inner layers.
   mbLg	The magnitude given in Other_mag1 is the local or regional magnitude. It is the body wave magnitude using the Lg wave.
   <Blank>	The type of magnitude given in Other_mag1 is unknown. The value came from Coffman, Jerry L., and von Hake, Carl A., 1973, Earthquake History of the United States: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, Publication 41-1, Revised Edition (Through 1970).

   Ref1

   A code identifying the source for the magnitude given in Other_mag1. The list of sources is provided in the text file quksigx_references.txt. (Source: National Atlas of the United States)

   Value	Definition
   <Blank>	No reference information is available.

   There is no predefined set of valid reference codes.

   Other_mag2

   The magnitude of the earthquake as reported by the source identified in Ref2. The type of magnitude is described by the attribute Type2. (Source: National Atlas of the United States)

   Value	Definition
   -9999.000	No additional magnitude measurement is available.

   Range of values
   Minimum:	2.900
   Maximum:	8.400

   Type2

   The type of magnitude recorded in the attribute Other_mag2, as defined by the source identified in Ref2. (Source: National Atlas of the United States)

   Value	Definition
   FA	The magnitude given in Other_mag2 is an estimated body wave magnitude. It is commonly computed from the felt area for earthquakes which occurred before seismic instruments were in general use.
   MD	The magnitude given in Other_mag2 is based on the duration or coda length of the earthquake vibration.
   ME	The magnitude given in Other_mag2 is the energy magnitude which is the radiated energy of the earthquake.
   ML	The magnitude given in Other_mag2 is the local magnitude, which is also known as the original "Richter" magnitude.
   MW	The magnitude given in Other_mag2 is the moment magnitude. It is the measure of total energy released by an earthquake.
   Mn	The magnitude given in Other_mag2 is the local or regional magnitude. It is the body wave magnitude using the Lg wave.
   Ms	The magnitude given in Other_mag2 is the surface wave magnitude. A surface wave is a seismic wave that travels along the Earth's surface.
   Mw	The magnitude given in Other_mag2 is the moment magnitude.
   UK	The magnitude type for the magnitude given in Other_mag2 is unknown.
   mb	The magnitude given in Other_mag2 is the body wave magnitude. A body wave is a seismic wave that travels through the Earth's inner layers.
   mbLg	The magnitude given in Other_mag2 is the local or regional magnitude. It is the body wave magnitude using the Lg wave.
   <Blank>	The type of magnitude given in Other_mag2 is unknown. The value came from Coffman, Jerry L., and von Hake, Carl A., 1973, Earthquake History of the United States: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, Publication 41-1, Revised Edition (Through 1970).

   Ref2

   A code identifying the source for the magnitude given in Other_mag2. The list of sources is provided in the text file quksigx_references.txt. (Source: National Atlas of the United States)

   Value	Definition
   <Blank>	No reference information is available

   There is no predefined set of valid references.

   Mmio

   Modified Mercalli Intensity (MMI), where the integer value represents the Roman numeral designation of the MMI intensity. (Source: U.S. Geological Survey)

   Value	Definition
   F	The earthquake was felt but no Modified Mercalli Intensity was assigned.
   2	An earthquake felt only by a few persons at rest, especially on upper floors of buildings. Delicately suspended objects may swing.
   3	An earthquake felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibration similar to the passing of a truck. Duration estimated in some cases.
   4	An earthquake felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.
   5	An earthquake felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.
   6	An earthquake felt by all; many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.
   7	An earthquake causing negligible damage in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by persons driving motor cars.
   8	An earthquake causing slight damage in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.
   9	An earthquake causing considerable damage in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.
   10	An earthquaking causing destruction of some well-built wooden structures; most masonry and frame structures destroyed with foundations. Railroad rails bent.
   11	An earthquake where few, if any (masonry) structures remain standing. Bridges destroyed. Railroad rails bent greatly.
   12	An earthquake where damage is total. Lines of sight and level distorted. Objects thrown into the air.

   Felt_area

   The area, in square kilometers, in which the earthquake was felt. (Source: National Atlas of the United States)

   Value	Definition
   <Blank>	The area in which the earthquake was felt is unknown.

   Range of values
   Minimum:	<1,000
   Maximum:	5,000,000

   Source

   The primary source of the earthquake information. (Source: National Atlas of the United States)

   Value	Definition
   EHUS1982	Coffman, J.L., von Hake, C.A., and Stover, C.W., 1982, Earthquake History of the United States: U.S. National Oceanic and Atmospheric Administration and U.S. Geological Survey, Publication No. 41-1, revised edition, [through 1980], 258p.
   MIDAS-IPGH	Tanner, J.G. and Shepherd, J.B., 1997, Project catalogue and seismic hazard maps, Seismic hazard in Latin America and the Caribbean: Panamerican Institute of Geography and History, v. 1, 143 p.
   PDE	Preliminary Determination of Epicenters, a list of earthquakes located by the National Earthquake Information Center of the U.S. Geological Survey and its predecessors in the U.S. Coast and Geodetic Survey, the National Oceanic Survey, and the Environmental Research Laboratories of the Department of Commerce. The PDE is comprised of final hypocenter and magnitude computations by the USGS NEIC published in monthly lists several months after the events.
   SUS	Stover, Carl W., and Coffman, Jerry L., 1993a, Seismicity of the United States, 1568-1989 (Revised): U.S. Geological Survey Professional Paper 1527, 418 p.

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • U.S. Geological Survey

2. Who also contributed to the data set?

   The following U.S. Geological Survey scientists contributed to this map layer: A. Tarr, M. Hopper, J. Dewey, M. McKeever, and N. Trevor.

3. To whom should users address questions about the data?
   Margaret G. Hopper
   U.S. Geological Survey
   MS966, Box 25046, Denver Federal Center
   Denver, CO 80225-0046
   USA
   

   303-273-8564 (voice)
   303-273-8600 (FAX)
   [email protected]
   

Why was the data set created?

These data are intended for geographic display and analysis at the national level, and for large regional areas. The data should be displayed and analyzed at scales appropriate for 1:2,000,000-scale data. No responsibility is assumed by the National Atlas of the United States or the U.S. Geological Survey in the use of these data. This map layer is intended for a mixed audience of specialists and non-specialists alike who have a need for general, non-technical information about significant United States earthquakes.

How was the data set created?

1. From what previous works were the data drawn?

   Seismicity of the United States (source 1 of 4)

   Stover, Carl W., and Coffman, Jerry L., 1993, Seismicity of the United States, 1568-1989 (Revised): Professional Paper 1527, U.S. Geological Survey, Washington, DC.

   Online Links:

   • <http://neic.usgs.gov/neis/epic/>

   Type_of_Source_Media: Paper

   Source_Contribution:

   Principal source of earthquake locations and attributes.

   PDE (source 2 of 4)

   U.S. Geological Survey, 200411, Preliminary Determination of Epicenters (PDE).

   Online Links:

   • <http://neic.usgs.gov/neis/epic/>

   Type_of_Source_Media: Online

   Source_Contribution:

   Supplemental source of earthquake locations and attributes.

   EHUS1982 (source 3 of 4)

   (ed.), J.L. Coffman , C.A. von Hake (ed.), and (ed.), C.W. Stover , 1982, Earthquake History of the United States: National Oceanic and Atmospheric Administration and U.S. Geological Survey, Boulder, CO.

   Type_of_Source_Media: Paper

   Source_Contribution:

   Supplemental source of earthquake locations and attributes.

   MIDAS-IPGH (source 4 of 4)

   Tanner, J.G., and Shepherd, J.B., 1997, Project catalogue and seismic hazard maps, Seismic hazard in Latin America and the Caribbean.

   Online Links:

   • <http://midas.uprm.edu>

   Type_of_Source_Media: Online

   Source_Contribution:

   Supplemental source of earthquake locations and attributes.

2. How were the data generated, processed, and modified?

   Date: Nov-2004 (process 1 of 1)

   Data for the years 1568 to 1989, from Seismicity of the United States, were combined with Preliminary Determination of Epicenters data for 1990 to 2004. EHUS1982 and MIDAS-IPGH were used to compile information for additional locations or for years not covered by the other sources. The resulting text file was loaded into ArcView and converted to a shapefile. Three records for Puerto Rico were dropped because they did not include values for longitude and latitude.

   Data sources used in this process:

   • Seismicity of the United States
   • PDE
   • EHUS1982
   • MIDAS-IPGH

3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?

   The attribute table was manually checked for unreasonable attribute values for depth and magnitude.

2. How accurate are the geographic locations?

   100 meter is the nominal precision of the reported instrumentally located coordinate values but accuracy is considerably less. Accuracy depends upon numerous factors including imprecision of the velocity model of the earth, uneven distribution of seismic stations, and imprecisions in the computational algorithm. Following initial proofreading of the input data file, a preliminary map of the locations of the earthquakes was produced which was examined for gross errors in spatial location.

3. How accurate are the heights or depths?

   Although depths are reported to the nearest 1 kilometer, the accuracy is considerably less owing to uncertainties in the velocity model of the Earth, uneven distribution of seismic stations, and imprecisions in the computational algorithm.

4. Where are the gaps in the data? What is missing?

   This map layer contains information on significant, historical earthquakes that caused deaths, property damage, geological effects, or that were experienced by populations in the epicentral area, for the United States, Puerto Rico, the U.S. Virgin Islands, Guam, and the Northern Mariana Islands. These data are limited to the best estimates of earthquake locations and to attributes such as magnitude and maximum intensity.

5. How consistent are the relationships among the observations, including topology?

   No formal tests for logical consistency were performed on this map layer, principally because the map layer contains attribute values that were arrived at by either or both quantitative (i.e. instrumental) and qualitative (i.e. historical) methods. Earthquakes that occurred prior to the introduction of seismological instrumentation are known only from written records, such as newspapers, books and journals, and diaries, which often may provide contradictory information that has to be carefully examined and weighed. As seismographs became more common in the early 1960's, the origin time and location were both more precisely and accurately determined but the compilation and evaluation of intensity reports was, and still is, a process that involves considerable subjectivity. As a result, all attributes associated with a given earthquake should be considered provisional and subject to further revision based on acquisition of new information and use of new analytical methods.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None

Use_Constraints:

None. Acknowledgment of the National Atlas of the United States of America and (or) the U.S. Geological Survey would be appreciated in products derived from these data.

1. Who distributes the data set? (Distributor 1 of 1)
   Earth Science Information Center, U.S. Geological Survey
   507 National Center
   Reston, VA 20192
   

   1-888-ASK-USGS (1-888-275-8747) (voice)
   

   Contact_Instructions:

   In addition to the address above there are other ESIC offices throughout the country. A full list of these offices is at <http://ask.usgs.gov/esic_index.html>.

2. What's the catalog number I need to order this data set?

3. What legal disclaimers am I supposed to read?

   Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made by the U.S. Geological Survey regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. No responsibility is assumed by the U.S. Geological Survey in the use of these data.

4. How can I download or order the data?
   • Availability in digital form:

     Data format:	ESRI Shapefile
     Network links:	<http://nationalatlas.gov/atlasftp.html?openChapters=chpgeol#chpgeol>

     Data format:	SDTS
     Network links:	<http://nationalatlas.gov/atlasftp.html?openChapters=chpgeol#chpgeol>

   • Cost to order the data: There is no charge for the map layer.

Who wrote the metadata?

Dates:

Last modified: 20-Jun-2006

Metadata author:

Gita Urban-Mathieux
National Atlas of the United States
12201 Sunrise Valley Dr
Reston, VA 20192

703-648-5175 (voice)
[email protected]

Metadata standard:

FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)