U.S. Seismic Design Maps - Documentation & Help

Motivation for the tool

The USGS collaborates with organizations that develop model building codes to make seismic design parameter values available to engineers. Although the USGS provides data files and maps of the gridded design values, most engineers need design values only at their building site. This tool provides the design values from the specified building code reference document at the specified site.

Help on input to the tool

Choosing a building code reference document

Users who are unsure which building code reference document and edition govern their project type and location should contact their local building department. Most municipalities adopt the International Building Code (in full, in part, or with amendments) and the AASHTO Guide Specifications for LRFD Seismic Bridge Design.

The U.S. Seismic Design Maps tool provides seismic design parameter values for the U.S. and its Territories from the following documents:

• International Building Code: 2012, 2009, and 2006
• ASCE/SEI 7 Standard: 2010 and 2005
• NEHRP Recommended Seismic Provisions: 2009 and 2003
• 2009 AASHTO Guide Specifications for LRFD Seismic Bridge Design

Selecting the Site Class

Users who do not know the site soil classification should consult their building code reference document. Each document provides guidance on how to use shear wave velocity, field standard penetration resistance, or shear strength data to classify the site soil. The USGS does not provide site soil classifications.

The U.S. Seismic Design Maps tool does not accommodate Site Class F. The design of structures at Site Class F locations generally requires the use of site-specific ground motion procedures, for example, detailed in Section 21.1 of the 2010 ASCE/SEI 7 Standard. The procedures for these site-specific cases are different from those used by the U.S. Seismic Design Maps tool.

Error messages

Error message: "Location Out of Bounds" - One (or both) of the site latitude and longitude values is (are) not valid. Please check that the longitude value is negative and the latitude value is positive. Also, the location must be within one of the following boxes (in degrees):

• latitude: 24.6 to 50; longitude: -125 to -65 (Conterminous U.S.)
• latitude: 48 to 72; longitude: -200 to -125.1 (Alaska)
• latitude: 18 to 23; longitude -161 to -154 (Hawaii)
• latitude: 17.5 to 19.8; longitude: -67.5 to -64.5 (Puerto Rico and the U.S. Virgin Islands)

Help on output from the tool

No output?

If output is not visible, the web browser may be blocking pop-up windows by default. The U.S. Seismic Design Maps tool provides output reports via a pop-up window. For help enabling pop-ups, please consult the browser-specific information at one of the following links: Chrome, Firefox, Internet Explorer, or Safari.

Does the printout of the Detailed Report appear incomplete?

If the lines, colors, or both in the Detailed Report are visible on the computer screen but not visible in a printed version, the browser may not be printing background colors. Please consult the following browser-specific instructions for assistance:

• Firefox (on a PC):
  • Select "File" in the upper-left corner of the main browser window.
  • Select "Page Setup."
  • Under the “Format & Options” tab, check the box next to the "Print Background" option.
• Firefox (on a Mac):
  • Select “File” in the the gray bar at the top of the screen.
  • Select “Print.”
  • In the “Appearance” section, check the boxes next to the “Print Background Colors” and “Print Background Images” options.
• Internet Explorer:
  • Select "File" in the upper-left corner of the main browser window.
  • Select "Page Setup."
  • Under "Paper Options," check the box next to the "Print Background Colors and Images" option.
• Safari:
  • Select "File" in the the gray bar at the top of the screen.
  • Select "Print."
  • Click the downward-pointing arrow appearing to the right of the Printer name.
  • Click the box next to "Print Backgrounds".

Design values versus hazard values

How do they differ?

The design values provided by the U.S. Seismic Design Maps tool are different than the USGS hazard values because the design values are the lesser of probabilistic and deterministic ground motion values. Also, for the 2009 NEHRP Recommended Seismic Provisions, the 2010 ASCE/SEI 7 Standard, and the 2012 International Building Code:

• the probabilistic values are risk-targeted rather than uniform-hazard ground motions;
• and both the probabilistic and deterministic values are defined in terms of maximum-direction rather than geometric-mean, horizontal spectral acceleration.

For more information, consult the references at the end of this web page.

How are design values calculated?

The USGS calculated the design values using:

1. hazard values computed by the USGS on a national scale and
2. site-specific procedures for seismic design stipulated in Chapter 21 of the NEHRP Recommended Seismic Provisions and the ASCE/SEI 7 Standard.

From both (1) and (2), the USGS derived national maps of design values for Site Class B. For the other site classes that may be specified by a user (that is, A, C, D, and E), the application adjusts the Site Class B design values using NEHRP “site coefficients.”

Design parameters in different building code reference documents

The seismic design parameters of the 2009 NEHRP Recommended Seismic Provisions, the 2010 ASCE/SEI 7 Standard, and the 2012 International Building Code are identical. The seismic design categories of the 2012 International Residential Code are derived from these parameters. However, the underlying uniform-hazard, risk coefficient, and deterministic parameters are only enumerated in the 2009 NEHRP Provisions. The 2010 ASCE/SEI 7 Standard also provides the risk coefficients in its site-specific ground motion procedures.

For more information about site and risk coefficients, see:

• Section C11.4.3 of Part 1 of the 2009 NEHRP Recommended Seismic Provisions and the additional information referenced there; and
• the conference paper by Luco and colleagues (2007) listed at the end of this web page.

Future updates

Include design values from:

• 2012/09/06/03/00 International Residential Code
• 2003/00 International Building Code
• 2002/98 ASCE/SEI 7 Standard
• 2000/97 NEHRP Recommended Provisions

Data access

Data from the tool can be accessed in XML format, using URLs like the following:

https://earthquake.usgs.gov/designmaps/us/inc/data-api.inc.php?latitude=40&longitude=-105&edition=ibc-2009&siteclass=3&riskcategory=0

Each parameter has a different set of options:

• latitude: Required; should be decimal degrees, with negative values south of the equator.
• longitude: Required, should be decimal degrees, with negative values west of the prime meridian.
• edition:

  ibc-2012

  2012 International Building Code

  asce-2010

  ASCE 7-10 Standard

  aashto-2009

  2009 AASHTO Guide Specifications for LRFD Seismic Bridge Design

  ibc-2009

  2006/2009 International Building Code

  nehrp-2009

  2009 NEHRP Recommended Seismic Provisions

  asce-2005

  ASCE 7-05 Standard

  nehrp-2003

  2003 NEHRP Recommended Seismic Provisions

• siteclass:

  0

  Site Class A

  1

  Site Class B

  2

  Site Class C

  3

  Site Class D

  4

  Site Class E

• riskcategory:

  0

  Risk Category I

  1

  Risk Category II

  2

  Risk Category III

  3

  Risk Category IV

Normal output will be contained within a <output> tag, while any errors will be a simple string within an <error> tag.

References

• Huang, Y. N., A.S. Whittaker & N. Luco (2008), “Maximum Spectral Demands in the Near-Fault Region,” Earthquake Spectra, Vol. 24, No. 1, pp. 319-341.
• Luco, N., B.R. Ellingwood, R.O. Hamburger, J.D. Hooper, J.K. Kimball & C.A. Kircher (2007), “Risk-Targeted versus Current Seismic Design Maps for the Conterminous United States,” Proceedings of the 2007 Structural Engineers Association of California Convention, Lake Tahoe, CA, pp. 163-175.
• Building Seismic Safety Council (2009), “NEHRP Recommended Seismic Provisions for New Buildings and Other Structures (FEMA P-750): Part I, Provisions,” Federal Emergency Management Agency, Washington, D.C., pp. 5-8, 10-18, 67-71, and 92-93 in particular.
• Petersen, M.D., A.D. Frankel, S.C. Harmsen, C.S. Mueller, K.M. Haller, R.L. Wheeler, R.L. Wesson, Y. Zeng, O.S. Boyd, D.M. Perkins, N. Luco, E.H. Field, C.J. Wills, & K.S. Rukstales (2008), “Documentation for the 2008 Update of the United States National Seismic Hazard Maps,” U.S. Geological Survey Open-File Report 2008-1128, 61 p.