Worldwide Seismic Design Values - Documentation & Help

Motivation for this tool

The USGS has received numerous requests for S_S 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 S_S and S₁ values from local, regional, and global studies and makes them available from one tool.

Important notes

The S_S 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 S_S 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.

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

Pins with gray stems and red, ball tops indicate data at particular locations. Click on a pin to view the information window.
The "location marker" is a large red arrow and can be moved to any location on the map. Drag the marker to the location of interest and drop it to show the information window.
A latitude and longitude pair can be entered in the search box at the top of the map. Latitudes should be in the range -90 to 90 decimal degrees, with negative values for the Southern Hemisphere. Longitudes should be in the range -180 to 180 decimal degrees, with negative values for the Western Hemisphere. The location marker will move to the latitude and longitude entered, and the information window will appear.
An address or partial address (for example, city or ZIP code) can be entered at the top of the map instead of a coordinate. Click on the link "Enter Address Instead," and an address input box will replace the coordinate input boxes. The location marker will move to the address entered, and the information window will appear. For a partial address, Google Maps finds a single point consistent with the partial address, and the Worldwide Seismic Design Values tool reports the S_S and S₁ values at that single point. The user can switch back to the coordinate input boxes by clicking "Enter Lat and Lon Instead."
The user's computer can provide its approximate location. In the address input bar, select "Geolocate Me." The location marker will move to the approximate location, and the information window will appear.

Each information window shows S_S 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.

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For Internet Explorer 8: If a pop-up window appears with the question "Do you want to view only the webpage content that was delivered securely?," please click "No."
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If you use Google Chrome and the application fails to load, please follow these steps.

Sources of S_S 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 S_S and S₁ from the PGA values provided by GSHAP, as described in the Approximate S_S and S₁ Values Section below. S_S and S₁ values of "No Data" or zero ("0") were removed.
Worldwide	GS of Canada Open File 5814	NA	173	The S_S and S₁ values are reproduced from Table 7 of the GSC OF 5814 report. At sites in Canada, the GSC based the S_S and S₁ values on the 2005 National Building Code of Canada. At sites in the U.S., the GSC used S_S and S₁ values from the 2009/06 International Building Code. At sites outside Canada and the U.S., the GSC estimated S_S 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 S_S 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: 2008 USGS OFR 1128 (Conterminous U.S.) 2007 USGS OFR 1043 (Alaska) Klein and colleagues (2001) "Seismic Hazard in Hawaii," Bulletin of the Seismological Society of America. (Hawaii) 2003 USGS NSHMP (Puerto Rico & U.S. Virgin Islands)
Outside the U.S. & its Territories	UFC 3-310-01, Change 2	NA	441	The S_S 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 S_S 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 S_S and S₁ Values Section below.
Haiti	2010 USGS OFR 1067	0.05	24,341	The USGS derived S_S and S₁ values following the procedure defined in the 2009/06 International Building Code. Each S_S and S₁ value is the minimum of probabilistic and deterministic hazard values.
Afghanistan	2007 USGS OFR 1137	0.1	34,881	The S_S 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 S_S 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 S_S 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 S_S 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 S_S 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, S_S 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 S_S and S₁ values

At many sites around the world, S_S and S₁ values are available from several datasets. The Worldwide Seismic Design Values tool reports S_S 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 S_S and S₁ values is not equivalent to the uncertainty in the S_S and S₁ value at a site. Some datasets adopt values from existing studies. In this case, at least two datasets will have the same S_S and S₁ values in the information window, but these are not independent reports of the design values.

If there are multiple S_S 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 S_S 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 S_S 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

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 S_S 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):

Exact Grid Point (P1). The requested location is at a grid point in the underlying dataset. The application returns the exact S_S and S₁ values at the grid point in the dataset.
Between Two Longitudes (P2). The requested location shares a latitude in the gridded dataset, but the location is between two gridded longitude values. The application returns S_S and S₁ values linearly interpolated between the two gridded points with the same latitude on either side of the location.
Between Two Latitudes (P3). The requested location shares a longitude in the gridded dataset, but the location is between two gridded latitude values. The application returns S_S and S₁ values linearly interpolated between the two gridded points with the same longitude on either side of the location.
Bounded by Four Grid Points (P4). The requested location is inside an imaginary box defined by four grid points in the dataset. The application performs a bilinear interpolation. First the S_S and S₁values are linearly interpolated between the northern pair of grid points and between the southern pair. Then these interpolated values are again interpolated to find the S_S and S₁ values at the requested latitude.

Future updates

Add data from:
- Canada (GS of Canada Open File 5813)
- New Zealand (NZ Standard 1170.5:2004)
- Mexico (2008 Manual of Civil Structures)
Add batch-mode functionality
Indicate the precision of S_S and S₁ values in the information window