SEISMIC DESIGN SPECTRAL ACCELERATION VALUES

“USGS96SA” — USGS 1996 SPECTRAL ACCELERATION VALUES

Program Description:

“USGS96SA” is a spreadsheet program written in MS-Excel for the purpose of determining the mapped
spectral acceleration values Ss and S1 to be used for seismic analysis and design in either the IBC 2000
or IBC 2003 Codes. Results may be obtained by input of location Zip Code or input of precise known
location latitude and longitude angles and are based on the 1996 USGS gridded data.

This program is a workbook consisting of two (2) worksheets, described as follows:

Worksheet Name Description
Doc This documentation sheet
USGS 1996 SA Values USGS 1996 spectral acceleration, Ss and S1 values

Program Assumptions and Limitations:

1. References are: a. “Seismic Design Parameters for Use with the 2000 International Building Code,
   2000 International Residential Code, 1997 NEHRP Seismic Design Provisons,
   and 1997 NEHRP Rehabilitation Guidelines” CD – Version 3.01
   by: E.V. Leyendecker, A.D. Frankel, and K.S. Rukstales
   Prepared by the U.S. Geological Survey (USGS) – February 2000
   Text file used for Lat. and Long. vs. Ss and S1 values only was: “MCE_10-48states.out”
   b. Interim User Guide for Seismic Design Parameters” – Version 4.00
   with “2003 NEHRP Recommended Provisions and FEMA 450” CD – June 2003
   by: E.V. Leyendecker, A.D. Frankel, and K.S. Rukstales
   Prepared by the U.S. Geological Survey (USGS) – June 2004
   Text file used for zip codes only was: “2003-Zip-Codes.txt”
   c. USGS Seismic Hazards internet web site located at:
   http://eqhazmaps.usgs.gov/
2. The Zip Code file listing from Reference “b” above was used instead of the Zip Code file from Reference “a”
   because it was more recent and contained many more entries.
3. The original Zip Code file listing used from Reference “b” above was modified to include only latitude angles
   between 24.6 (rounded) and 50 degrees, as well as only longitude angles between -125 and -65 degrees.
4. The USGS 1996 gridded values for mapped spectral accelerations, Ss and S1, from Reference “a” above are
   the values used in creating the maps that appear both in the IBC 2000 and IBC 2003 Codes. The values for
   Ss and S1 based on the Zip Code are for the latitude and longitude at the centroid of the Zip Code area.
   Since these spectral acceleration values may vary widely within a particular Zip Code, the user is advised to
   get the precise latitude and longitude of the project location for the most accurate results.