Worldwide Seismic Design Values - Documentation & Help

Motivation for this tool

The USGS has received numerous requests for SS and S1 values at sites around the world, not just in the U.S. and its Territories. The Worldwide Seismic Design Values tool collects published SS and S1 values from local, regional, and global studies and makes them available from one tool.

Important notes

The SS and S1 values provided by this tool should be consistent with those from a local study. Nonetheless, the design values in this tool never supersede those in the governing building code or from a site-specific analysis.

The seismic design procedures of local or national building codes might require design parameters other than SS and S1. The user is responsible for knowing what seismic design parameters are required by the applicable building code.

Help using the tool

The user interface of the Worldwide Seismic Design Values tool is a Google Map. A user can pan and zoom the map, like any other Google Map, either by using the pan and zoom controls, by dragging the map, or by double-clicking on a location. If the red "location marker" is no longer visible after panning or zooming, the location marker automatically moves to the center of the new viewport.

Shaded red boxes indicate regional, gridded datasets. The Global Seismic Hazard Assessment Program data are not indicated by a red box as they cover most locations of the globe.

SS and S1 values are available in an information window by querying the map in several ways:

Each information window shows SS and S1 values at the selected location from all available datasets.

Error message: "No point data exists for this location" - There is no dataset covering the selected site. This is most likely to occur in ocean areas and near the poles, where even GSHAP data are unavailable.

If you use Internet Explorer and cannot see the Google Map, please read the information below. This issue results from Internet Explorer's security settings, and the USGS is currently working to address it. Individuals using other browsers, such as Firefox, Chrome, or Safari, will not experience this problem.

If you use Google Chrome and the application fails to load, please follow these steps.

Sources of SS and S1 values

Region Dataset Grid spacing (deg) Number of locations Notes
Worldwide Global Seismic Hazard Assessment Program 0.1 5,367,600 These data are not an exact copy of the GSHAP database:
  • The USGS approximated SS and S1 from the PGA values provided by GSHAP, as described in the Approximate SS and S1 Values Section below.
  • SS and S1 values of "No Data" or zero ("0") were removed.
Worldwide GS of Canada Open File 5814 NA 173 The SS and S1 values are reproduced from Table 7 of the GSC OF 5814 report. At sites in Canada, the GSC based the SS and S1 values on the 2005 National Building Code of Canada. At sites in the U.S., the GSC used SS and S1 values from the 2009/06 International Building Code. At sites outside Canada and the U.S., the GSC estimated SS and S1 values from the Global Seismic Hazard Assessment Program.
U.S. & its Territories 2009/06 International Building Code
  • 0.05 (Conterminous U.S.)
  • 0.1 (Alaska)
  • 0.02 (Hawaii)
  • 0.05 (Puerto Rico & U.S. Virgin Islands)
  • 611,309 (Conterminous U.S.)
  • 132,821 (Alaska)
  • 88,101 (Hawaii)
  • 16,261 (Puerto Rico & U.S. Virgin Islands)
The SS and S1 values are reproduced from the Maximum Considered Earthquake ground motion maps in the 2009/06 International Building Code. The USGS derived these design values from the following hazard studies using the IBC procedure to convert hazard values to design values:
Outside the U.S. & its Territories UFC 3-310-01, Change 2 NA 441 The SS and S1 values reported here are reproduced from Tables D-2 and E-1 of Unified Facilities Criteria 3-310-01, Change 2. The data are not provided on a regular grid but rather given at selected locations outside the U.S. and its Territories. The SS and S1 values may have been approximated from peak ground acceleration values with a 10% probability of exceedance in 50 years, as described in the Approximate SS and S1 Values Section below.
Haiti 2010 USGS OFR 1067 0.05 24,341 The USGS derived SS and S1 values following the procedure defined in the 2009/06 International Building Code. Each SS and S1 value is the minimum of probabilistic and deterministic hazard values.
Afghanistan 2007 USGS OFR 1137 0.1 34,881 The SS and S1 values are spectral accelerations with a 2% probability of exceedance in 50 years. The USGS has not calculated deterministic values in this region, which would be used according to the International Building Code procedure to cap these probabilistic values.
Southeast Asia 2007 USGS Administrative Report 0.1 66,581
  • This dataset merges the Java/Sumatra and Southeast Asia datasets. Where the datasets overlap, the data from the Southeast Asia dataset are used.
  • Reference: Mark Petersen, Stephen Harmsen, Charles Mueller, Kathleen Haller, James Dewey, Nicolas Luco, Anthony Crone, David Lidke, and Kenneth Rukstales. Documentation for the Southeast Asia Seismic Hazard Maps, 30 September 2007, 61p.
  • The SS and S1 values are spectral accelerations with a 2% probability of exceedance in 50 years. The USGS has not calculated deterministic values in this region, which would be used according to the International Building Code procedure to cap these probabilistic values.
Please request other datasets.

Approximate SS and S1 values

Some datasets provide peak ground acceleration (PGA) values with a 10% probability of exceedance in 50 years. For the Global Seismic Hazard Assessment Program dataset and some sites in the Unified Facilities Criteria dataset, the Worldwide Seismic Design Values tool provides approximate SS and S1 values derived from PGA values. This tool uses the following approximations. PGA values with a 2%-in-50-year exceedance are approximately twice the PGA values with a 10%-in-50-year exceedance. The SS value is 2.5 times the 2%-in-50-year PGA value, and the S1 value is roughly equivalent to the 2%-in-50-year PGA value. Thus, SS is approximately 5.0 times the 10%-in-50-year PGA, and S1 is approximately 2.0 times the 10%-in-50-year PGA.

Multiple SS and S1 values

At many sites around the world, SS and S1 values are available from several datasets. The Worldwide Seismic Design Values tool reports SS and S1 values from all available datasets in an unordered list. The dataset listing in the information window does not imply preference for one dataset over another. Also, the variability (or consistency) in SS and S1 values is not equivalent to the uncertainty in the SS and S1 value at a site. Some datasets adopt values from existing studies. In this case, at least two datasets will have the same SS and S1 values in the information window, but these are not independent reports of the design values.

If there are multiple SS and S1 values available at the site of interest, the user should choose the most appropriate source of information for the design project. The user might consider choosing the dataset that is the most specific to the site. For example, the USGS performed a seismic hazard analysis specifically for Afghanistan, but the Global Seismic Hazard Assessment Program dataset also covers the country. The SS and S1 values from the USGS dataset would be more specific to sites in Afghanistan than the values from the GSHAP dataset. Similarly, if two or more country-specific datasets overlap (for example, near an international border), the SS and S1 values from the dataset associated with the country where the project will be built would be more specific to the site than any dataset associated with another country.

Unpopulated areas

The Global Seismic Hazard Assessment Program dataset is the primary source used for unpopulated areas (as well as many populated areas). Though this dataset does not cover the entire world, it does cover a significant portion of it.

Spatial interpolation

interpolation

Example gridded dataset (black dots) and the four types of requested locations (red dots).

If a user selects a location with one or more underlying datasets on a grid, the application uses a bilinear interpolation method to return the SS and S1 values associated with the location from each gridded dataset. A selected location falls into one of four categories (labeled in the figure at right):

Future updates