National Atlas
of the United States
Seismic Events: Map Layer Description File
This map layer includes a selection of seismic events above 4.0 magnitude in and near the United States for the years 1973-1998. The Seismic Events map layer was compiled by the U.S. Geological Survey from a database maintained by its National Earthquake Information Center.

The magnitude of the earthquake is a logarithmic measure of its "size." This is commonly referred to as the "Richter scale".

Download this map layer in Shapefile format.

Download this map layer in SDTS format.

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Metadata

What follows is very detailed technical information about this map layer. This is often called metadata. Metadata (or "data about data") describe the content, quality, condition, and other characteristics of data. Metadata are used to organize and maintain investments in data, to provide information to data catalogs and clearinghouses, and to aid data transfers. The Federal Geographic Data Committee (FGDC) publishes the Content Standard for Digital Geospatial Metadata. Many organizations within and outside of the federal government have adopted the FGDC metadata standard and are using automated indexing and serving mechanisms to provide access to their holdings through the Internet. Visit the FGDC Clearinghouse to learn more about how metadata is used in clearinghouses and to search for other data sets. 

Identification Information 
Data Quality Information 
Spatial Data Organization Information 
Spatial Reference Information 
Entity and Attribute Information 
Distribution Information 
Metadata Reference Information 

Identification Information: 
Citation: 
Citation_Information: 
Originator: U.S. Geological Survey (USGS) 
Publication_Date: 1996 
Title: Earthquakes 
Publication_Information: 
Publication_Place: Reston, Virginia 
Publisher: U.S. Geological Survey 
  
Description: 
Abstract: 
This data set includes a selection of seismic events above 4.0 magnitude in and near the United States for the years 1973-1998. 
Purpose: 
The digital data sets are used to create electronic and hard copy maps that depict various aspects of the nation. The data can be used to conduct geographic analysis on national and large regional scales. The digital data will provide a basis from which future revisions of the atlas can be derived. 
Supplemental_Information: 
Revisions: 1) 6/29/98 - Corrected ellipsoid name from WGS84 to GRS1980 and changed flattening ratio. 
  

Time_Period_of_Content: 
Time_Period_Information: 
Single_Date/Time: 
Calendar_Date: 1998 
Currentness_Reference: publication date 
  
Status: 
Progress: Complete 
Maintenance_and_Update_Frequency: Irregular 
  
Spatial_Domain: 
Bounding_Coordinates: 
West_Bounding_Coordinate: 172.0 
East_Bounding_Coordinate: -66.0 
North_Bounding_Coordinate: 72.0 
South_Bounding_Coordinate: 18.0 
  
Keywords: 
Theme: 
Theme_Keyword_Thesaurus: None 
Theme_Keyword: seismic 
Theme_Keyword: earthquakes 
Place: 
Place_Keyword_Thesaurus: 
U.S. Department of Commerce, 1995, Countries, dependencies, areas of special sovereignty, and their principal administrative divisions (Federal Information Processing Standard (FIPS) 10-4): Washington, D.C., National Institute of Standards and Technology. 
Place_Keyword: United States 
  
Access_Constraints: None 
Use_Constraints: 
None. Acknowledgment of the National Earthquake Information Center (NEIC) would be appreciated in products derived from these data. 
Point_of_Contact: 
Contact_Information: 
Contact_Person_Primary: 
Contact_Person: Bruce Wright 
Contact_Organization: U.S. Geological Survey 
Contact_Address: 
Address_Type: mailing address 
Address: 521 National Center 
City: Reston 
State_or_Province: VA 
Postal_Code: 20192 
Contact_Voice_Telephone: 703-648-4528 
Contact_Electronic_Mail_Address: bwright@usgs.gov 
  

Data Quality Information: 
Logical_Consistency_Report: 
No tests for logical consistency were performed on this data set. 
Completeness_Report: 
This data set includes all seismic events in and near the United States. No tests for completeness were performed on this data set. 
Lineage: 
Source_Information: 
Source_Citation: 
Citation_Information: 
Originator: 
National Earthquake Information Center (NEIC), USGS-Geologic Division 
Publication_Date: 1998 
Title: Earthquake data base 
Publication_Information: 
Publication_Place: Golden, CO 
Publisher: USGS 
Type_of_Source_Media: online 
Source_Time_Period_of_Content: 
Time_Period_Information: 
Range_of_Dates/Times: 
Beginning_Date: 1973 
Ending_Date: 1998 
Source_Currentness_Reference: publication date 
Source_Citation_Abbreviation: n/a 
Source_Contribution: spatial and attribute information 
Process_Step: 
Process_Description: 
The data were extracted from the NEIC Earthquake Search WWW site at: <http://wwwneic.cr.usgs.gov/neis/epic/epic.html.> The data were then loaded into an INFO database. Latitude and Longitude values were written to an external file and used as input to the ARC/INFO command GENERATE to create a point coverage. The remaining attributes were joined to the data using the command JOINITEM. A bounding rectangle was used to isolate just those earthquakes located in the area of interest, standard tics were added and point topology was build. A spot check was conducted to validate that the proper attributes were associated with the earthquake locations. 
Process_Date: 1998 
  

Spatial Data Organization Information: 
Direct_Spatial_Reference_Method: Vector 
Point_and_Vector_Object_Information: 
SDTS_Terms_Description: 
SDTS_Point_and_Vector_Object_Type: Point 
Point_and_Vector_Object_Count: 26867 
  

Spatial Reference Information: 
Horizontal_Coordinate_System_Definition: 
Geographic: 
Latitude_Resolution: 0.01 
Longitude_Resolution: 0.01 
Geographic_Coordinate_Units: Decimal Degrees 
Geodetic_Model: 
Horizontal_Datum_Name: North American Datum of 1983 
Ellipsoid_Name: GRS1980 
Semi-major_Axis: 6378137 
Denominator_of_Flattening_Ratio: 298.257222 
  

Entity and Attribute Information: 
Detailed_Description: 
Entity_Type: 
Entity_Type_Label: QUAKESX020.PAT 
Entity_Type_Definition: Point attribute table 
Entity_Type_Definition_Source: ARC/INFO 
Attribute: 
Attribute_Label: AREA 
Attribute_Definition: Point 
Attribute_Definition_Source: Computed 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: 0.0 
Enumerated_Domain_Value_Definition: n/a 
Enumerated_Domain_Value_Definition_Source: n/a 
Attribute: 
Attribute_Label: PERIMETER 
Attribute_Definition: Point 
Attribute_Definition_Source: Computed 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: 0.0 
Enumerated_Domain_Value_Definition: n/a 
Enumerated_Domain_Value_Definition_Source: n/a 
Attribute: 
Attribute_Label: QUAKESX020# 
Attribute_Definition: Internal feature number 
Attribute_Definition_Source: Computed 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: Sequential unique positive integer 
Enumerated_Domain_Value_Definition: n/a 
Enumerated_Domain_Value_Definition_Source: n/a 
Attribute: 
Attribute_Label: QUAKESX020-ID 
Attribute_Definition: User-assigned feature number 
Attribute_Definition_Source: User-defined 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: Integer 
Enumerated_Domain_Value_Definition: n/a 
Enumerated_Domain_Value_Definition_Source: n/a 
Attribute: 
Attribute_Label: CATALOG_SRC 
Attribute_Definition: Contributing source of earthquake data 
Attribute_Definition_Source: NEIC 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: 
PDE = Contributed by USGS NEIC, Preliminary Determination of Epicenters - Monthly Listing 
Enumerated_Domain_Value_Definition: 
Contributed by USGS NEIC, Preliminary Determination of Epicenters - Monthly Listing 
Enumerated_Domain_Value_Definition_Source: NEIC 
Attribute: 
Attribute_Label: YEAR 
Attribute_Definition: Year of the event 
Attribute_Definition_Source: NEIC 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: 1973-1998 
Enumerated_Domain_Value_Definition: n/a 
Enumerated_Domain_Value_Definition_Source: NEIC 
Attribute: 
Attribute_Label: MONTH 
Attribute_Definition: Month of the event 
Attribute_Definition_Source: NEIC 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: 1-12 
Enumerated_Domain_Value_Definition: n/a 
Enumerated_Domain_Value_Definition_Source: n/a 
Attribute: 
Attribute_Label: DAY 
Attribute_Definition: Day of the event 
Attribute_Definition_Source: NEIC 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: 1-31 
Enumerated_Domain_Value_Definition: n/a 
Enumerated_Domain_Value_Definition_Source: n/a 
Attribute: 
Attribute_Label: ORIGIN_TIME 
Attribute_Definition: 
Time of the event in Universal Time Coordinated (UTC) in hours, minutes, seconds, and decimal seconds expressed as a single real number. 
Attribute_Definition_Source: NEIC 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: 000000.0 - 235959.9 
Enumerated_Domain_Value_Definition: n/a 
Enumerated_Domain_Value_Definition_Source: n/a 
Attribute_Units_of_Measure: decimal degrees 
Attribute: 
Attribute_Label: LAT 
Attribute_Definition: Latitude of earthquake 
Attribute_Definition_Source: NEIC 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: 0-90 
Enumerated_Domain_Value_Definition: n/a 
Enumerated_Domain_Value_Definition_Source: n/a 
Attribute_Units_of_Measure: decimal degrees 
Attribute: 
Attribute_Label: LON 
Attribute_Definition: Longitude of earthquake 
Attribute_Definition_Source: NEIC 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: -180 to 0 and 155 to 180 
Enumerated_Domain_Value_Definition: n/a 
Enumerated_Domain_Value_Definition_Source: n/a 
Attribute: 
Attribute_Label: DEPTH 
Attribute_Definition: Depth of earthquake in kilometers 
Attribute_Definition_Source: NEIC 
Attribute_Domain_Values: 
Range_Domain: 
Range_Domain_Minimum: 0 
Range_Domain_Maximum: 634 
Attribute_Units_of_Measure: Kilometers (rounded up to nearest) 
Attribute: 
Attribute_Label: MAGNITUDE 
Attribute_Definition: 
Magnitude of the earthquake. It is a logarithmic measure of the "size" of an earthquake. Commonly referred to as the "Richter scale". 
Attribute_Definition_Source: NEIC 
Attribute_Domain_Values: 
Range_Domain: 
Range_Domain_Minimum: 4.0 
Range_Domain_Maximum: 8.10 
Attribute: 
Attribute_Label: MAG_SCALE 
Attribute_Definition: Magnitude scale 
Attribute_Definition_Source: NEIC 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: 
Parameters that apply to the magnitude value. See NEIC WWW site for more information: <http://wwwneic.cr.usgs.gov/neis/epic/code_magnitude.html> 
Enumerated_Domain_Value_Definition_Source: NEIC 
Attribute: 
Attribute_Label: MAG_SOURCE 
Attribute_Definition: 
Two and three letter acronyms of the source of the magnitude data. See the NEIC WWW site for more information (<http://wwwneic.cr.usgs.gov/neis/epic/code_magnitude.html).> 
Attribute_Definition_Source: NEIC 
Attribute_Domain_Values: 
Enumerated_Domain: 
Enumerated_Domain_Value: Various two and three letter acronyms 
Enumerated_Domain_Value_Definition: n/a 
Enumerated_Domain_Value_Definition_Source: 
National Earthquake Information Center 
  

Overview_Description: 
Entity_and_Attribute_Overview: 
The point attribute table: 
 Column
 Item Name
 Width
 Output
 Type
 N. Dec.
 
 1
 AREA 4 12 F 3 
 5
  PERIMETER  4  12  F  3 
9 
  QUAKESX020#  4  5  B  - 
13   QUAKESX020-ID  4  5  B  - 
17   CATALOG_SRC  3 3  C -  
20 YEAR 4 4  I  - 
24 MONTH 2 2 I  - 
26 DAY 2 2 I  - 
28 ORIGIN_TIME 4 12 F 2 
33
 LAT 4 12 F 2 
36  LON 4 12 F 2 
40 DEPTH 4 4 I - 
44 MAGNITUDE 4 12 F 2 
48 MAG_SCALE 2 2 C - 
50 MAG_SOURCE 2 2 C - 

  
Entity_and_Attribute_Detail_Citation: n/a 
  

Distribution Information: 
Distributor: 
Contact_Information: 
Contact_Person_Primary: 
Contact_Person: Bruce Wright 
Contact_Organization: U.S. Geological Survey 
Contact_Address: 
Address_Type: mailing address 
Address: 521 National Center 
City: Reston 
State_or_Province: VA 
Postal_Code: 20192 
Contact_Voice_Telephone: 703-648-4528 
Contact_Electronic_Mail_Address: bwright@usgs.gov 
  
Distribution_Liability: 
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 USGS regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. 
Metadata Reference Information: 
Metadata_Date: 19980514 
Metadata_Contact: 
Contact_Information: 
Contact_Person_Primary: 
Contact_Person: Bruce Wright 
Contact_Organization: U.S. Geological Survey 
Contact_Address: 
Address_Type: mailing address 
Address: 521 National Center 
City: Reston 
State_or_Province: VA 
Postal_Code: 20192 
Contact_Voice_Telephone: 703-648-4528 
Contact_Electronic_Mail_Address: bwright@usgs.gov 
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata 
Metadata_Standard_Version: 19940608 
Metadata_Security_Information: 
Metadata_Security_Classification_System: None 
Metadata_Security_Classification: Unclassified 
Metadata_Security_Handling_Description: None 

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U.S. Geological Survey
National Atlas of the United States and The National Atlas of the United States of America are trademarks of the United States Geological Survey.
URL: http://www.nationalatlas.gov/quakesmt.html
Public access to these map layers is provided by the EROS Data Center
Comments and feedback: atlasmail
Last modification: 02JUN99 bum