Seismic-Hazard Maps for Alaska and the Aleutian Islands: 3HZ250

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Frequently anticipated questions:


What does this data set describe?

Title: Seismic-Hazard Maps for Alaska and the Aleutian Islands: 3HZ250
Abstract:
Probabilistic seismic hazard maps were prepared for Alaska portraying peak horizontal ground acceleration and horizontal spectral response acceleration for 0.2, 0.3, and 1.0 second periods with probabilities of exceedance of 10% in 50 years and 2% in 50 years. This particular data set is for horizontal spectral response acceleration for 0.3 second period with a 2% probability of exceedance in 50 years. All of the maps were prepared by combining hazard derived from spatially- smoothed historic seismicity with hazard from fault-specific sources. The acceleration values contoured are the random horizontal component. The reference site condition is firm rock, defined as having an average shear-wave velocity of 760 m/sec in the top 30 meters corresponding to the boundary between NEHRP site classes B and C.
This data set represents the results of calculations of hazard curves for a grid of points with a spacing of 0.1 degrees in latitude and longitude. The grid of points were contoured to produce the final representation of the seismic-hazard.
Supplemental_Information:
A description of how the underlying geologic and geophysical data were prepared as well as the methodology used in calculating hazard for a geographic location can be found in the following report:
Wesson, Robert, Frankel, Arthur, Mueller, Charles, and Harmsen, Stephen, 1999, Probabilistic Seismic Hazard Maps of Alaska: U.S. Geological Survey Open-File Report 99-36, 48 p.
  1. How might this data set be cited?
    Wesson, Robert L., Frankel, Arthur D., Mueller, Charles S., Harmsen, Stephen C., and Rukstales, Kenneth S. (compiler), 1999, Seismic-Hazard Maps for Alaska and the Aleutian Islands: 3HZ250: U.S. Geological Survey Geologic Investigations Series I-2679, U.S. Geological Survey, Denver, Colorado.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: 170.0
    East_Bounding_Coordinate: -130.0
    North_Bounding_Coordinate: 72.0
    South_Bounding_Coordinate: 50.0
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 1999
    Currentness_Reference:
    publication date
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: map
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • Point (105)
      • String (218)
      • GT-polygon composed of chains (106)
    2. What coordinate system is used to represent geographic features?
      The map projection used is Albers Conical Equal Area.
      Projection parameters:
      Standard_Parallel: 55
      Standard_Parallel: 65
      Longitude_of_Central_Meridian: -160
      Latitude_of_Projection_Origin: 0
      False_Easting: 0.00000
      False_Northing: 0.00000
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.0001
      Ordinates (y-coordinates) are specified to the nearest 0.0001
      Planar coordinates are specified in Meters
      The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.4.
      The flattening of the ellipsoid used is 1/294.98.
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    Attribute items are in ARC/INFO feature class format.  Additional
    items that were added to the data are:
    
    POLYGON
    
    attribute        description
    =========	===========
    acc_val	      Acceleration value in percent of gravity of the
                     polygon.  The polygon represents the range of
                     acceleration values that are contained within its
                     borders.  The polygon is assigned the lowest value
                     allowed within the polygon's borders.  The range of
                     values allowed within a polygon is controlled by the
                     contours.  Valid values are:  0,4,8,12,16,20,24,28,32,
                     36,40,60,80,100,120,160,240,320,400
    
    valley		A topological indicator that tells whether the area
                     contained within the polygon is a local minima (valley)
                     or not.  A value of "1" indicates the area is a local
                     minima.
    LINE
    
    attribute 	description
    =========	===========
    acc_val	      Acceleration value in percent of gravity that the
                     contour represents.  Valid values are: 0,4,8,12,16,20,
                     24,28,32,36,40,60,80,100,120,160,240,320,400
    
    valley		A topological indicator that tells whether the area
                     contained within the contour is a local minima (valley)
                     or not.  A value of "1" indicates the area is a local
                     minima.
    
    Entity_and_Attribute_Detail_Citation: none

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Wesson, Robert L.
    • Frankel, Arthur D.
    • Mueller, Charles S.
    • Harmsen, Stephen C.
    • Rukstales, Kenneth S. (compiler)
  2. Who also contributed to the data set?
    We thank Max Wyss and Stefan Wiemer of the Geophysical Institute, University of Alaska, and John Lahr of the U.S. Geological Survey for their help with seismicity catalogs. Ken Rukstales prepared the ARC/INFO data and formatted the GIS versions of the maps.
  3. To whom should users address questions about the data?
    Ken Rukstales
    U.S. Geological Survey
    Box 25046, Mail Stop 966
    Denver, Colorado
    USA

    303-273-8677 (voice)
    303-273-8600 (FAX)
    rukstales@usgs.gov
    Contact_Instructions: Best to contact via e-mail or telephone

Why was the data set created?

This map is intended to summarize the available quantitative information about seismic ground motion hazard in Alaska from geologic and geophysical sources.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 1999 (process 1 of 2)
    The data to produce the maps were originally an ASCII file of grid points having a latitude and longitude spacing of 0.1 degrees. Each grid point had an associated acceleration value calculated from the prescribed seismological model. The data were imported into a grid and then contoured using ARC/INFO. The desired final contours were selected and polygon and arc topology were ascertained as well as appropriate feature attributes. Person who carried out this activity:
    Ken Rukstales
    U.S. Geological Survey
    Box 25046, Mail Stop 966
    Denver, Colorado
    USA

    303-273-8677 (voice)
    303-273-8600 (FAX)
    rukstales@usgs.gov
    Contact_Instructions: Best to contact via e-mail or telephone
    Date: 10-Jun-1999 (process 2 of 2)
    Creation of original metadata record Person who carried out this activity:
    U.S. Geological Survey
    Attn: Ken Rukstales
    Box 25046, Mail Stop 966
    Denver, Colorado
    USA

    303-273-8677 (voice)
    303-273-8600 (FAX)
    rukstales@usgs.gov
  3. What similar or related data should the user be aware of?
    Wesson, Robert L., Frankel, Arthur D., Mueller, Charles S., and Harmsen, Stephen C., 1999, Probabilistic Seismic Hazard Maps of Alaska: U.S. Geological Survey Open-File Report 99-36, U.S. Geological Survey, Denver, Colorado.


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

  1. How well have the observations been checked?
    Calculation of the acceleration values is described in the following report:
    Wesson, Robert, Frankel, Arthur, Mueller, Charles, and Harmsen, Stephen, 1999, Probabilistic Seismic Hazard Maps of Alaska: U.S. Geological Survey Open-File Report 99-36, 48 p.
    The hazard maps do not consider uncertainty in the underlying seismicity or fault parameters.
  2. How accurate are the geographic locations?
    The location of features is based on theoretical calculations of a seismological model for the study area. The location of each point is considered to be correct within the confines of computer accuracy.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Areas outside of Alaska and the Aleutian Islands have been removed.
  5. How consistent are the relationships among the observations, including topology?
    Polygon and chain-node topology present.

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:
The data are not to be used for areas outside of Alaska and the Aleutian Islands.
  1. Who distributes the data set? (Distributor 1 of 2)
    U.S. Geological Survey, Information Services
    Box 25286, Mail Stop 306
    Denver, Colorado
    USA

    1-888-ASK-USGS (voice)
    303-202-4693 (FAX)
  2. What's the catalog number I need to order this data set? U.S. Geological Survey Geologic Investigations Series I-2679 (Sheet 2 of 2) Seismic-Hazard Maps For Alaska and the Aleutian Islands, Sheet2, 2% Probability of Exceedance in 50 Years For Peak Horizontal Acceleration and Horizontal Spectral Response Acceleration For 0.2, 0.3, and 1.0 Second Periods (5% of Critical Damping)
  3. What legal disclaimers am I supposed to read?
    Although these data have been used by the U.S. Geological Survey, no warranty, expressed or implied is made by the USGS as to the accuracy of the data and related material nor shall the fact of distribution constitute any such warranty, and no responsibility is assumed by the USGS in connection therewith.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: U.S. Geological Survey Geologic Investigations Series I-2679 (Sheet 2 of 2)
      Seismic-Hazard Maps For Alaska and the Aleutian Islands, Sheet2, 2% Probability of Exceedance in 50 Years For Peak Horizontal Acceleration and Horizontal Spectral Response Acceleration For 0.2, 0.3, and 1.0 Second Periods (5% of Critical Damping) in format PDF (version version 4.0) Adobe Portable Document Format
      Network links: http://pubs.usgs.gov/imap/i-2679/i2679-2.pdf
    • Cost to order the data: none


  1. Who distributes the data set? (Distributor 2 of 2)
    U.S. Geological Survey
    Attn: Ken Rukstales
    Box 25046, Mail Stop 966
    Denver, Colorado
    USA

    303-273-8677 (voice)
    rukstales@usgs.gov
    Contact_Instructions: Best to contact via e-mail or telephone
  2. What's the catalog number I need to order this data set? Downloadable geospatial data sets in ARC/INFO export format are available.
  3. What legal disclaimers am I supposed to read?
    Although these data have been used by the U.S. Geological Survey, no warranty, expressed or implied is made by the USGS as to the accuracy of the data and related material nor shall the fact of distribution constitute any such warranty, and no responsibility is assumed by the USGS in connection therewith.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: Seismic-Hazard Map For Alaska and the Aleutian Islands, 2% Probability of Exceedance in 50 Years For Horizontal Spectral Response Acceleration For 0.3 Second Period (5% of Critical Damping) in format ARCE (version 7.2.1) Size: 0.1367
      Network links: http://pubs.usgs.gov/imap/i-2679/ak3hz250.e00.gz
    • Cost to order the data: none


Who wrote the metadata?

Dates:
Last modified: 13-Jun-2016
Last Reviewed: 1999
Metadata author:
Peter N Schweitzer
USGS Midwest Area
Collection manager, USGS Geoscience Data Clearinghouse, http://geo-nsdi.er.usgs.gov/
Mail Stop 954
12201 Sunrise Valley Dr
Reston, VA
USA

703-648-6533 (voice)
703-648-6252 (FAX)
pschweitzer@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://geo-nsdi.er.usgs.gov/metadata/map-i/2679/3HZ250.faq.html>
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