U.S. Seismic Design Maps

For occasional announcements about this web tool, please visit our U.S. Seismic Design Maps wiki.

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Soon, the American Society of Civil Engineers (ASCE) will release an erratum for ASCE Standard 7-10 that affects this web application.

The peak ground acceleration (PGA) maps in the first two printings of ASCE 7-10 were developed using 0.6g for the floor of the deterministic cap, whereas the site-specific ground motion procedure (Section 21.5) specified 0.5g. In the third and subsequent printings, the PGA maps will be based on the 0.5g floor, consistent with the site-specific procedure. In anticipation of this change, on December 12 of 2012 the floor of the deterministic PGA cap used in this web application was lowered to 0.5g for the 2010 ASCE 7 “Design Code Reference Document” option.

Prematurely, the floor was also lowered for the 2009 NEHRP option. Although the ASCE 7-10 erratum might ultimately be adopted by the developers of the 2009 NEHRP Provisions, for the time being the PGA maps in the Provisions still reflect a 0.6g floor.

Thus, as of April 2 of 2013, the floor of the deterministic PGA cap for the 2009 NEHRP option of this web application has been reset to 0.6g. The floor for the 2010 ASCE 7 option remains 0.5g.