U.S. Seismic Design Maps
Due to insufficient resources and the recent development of similar web tools by third parties, this spring the USGS will be streamlining the two U.S. Seismic Design Maps web applications, including the one below. Whereas the current applications each interact with users through a graphical user interface (GUI), the new web services will receive the inputs (e.g. latitude and longitude) in the form of a web address and return the outputs (e.g. SDS and SD1) in text form, without supplementary graphics. Though designed primarily to be read by the aforementioned third-party web GUIs, the text outputs are also human-readable. To preview the new web services, please click here. Step-by-step instructions for using one of these web services, namely that for the recently published 2016 ASCE 7 Standard, are posted here.
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.