Statistically Derived Design Spectra


Elastic design response spectra can be predicted in the same statistical manner as ground motion parameters such as peak ground acceleration or velocity. Numerous researchers have developed attenuation relationships for elastic spectra, which are listed in the references.

The general procedure for generating statistically derived spectra is as follows:

  • Classes of ground motions are selected (based on soil, magnitude, distance, etc.)
  • Response spectra for a large number of corresponding ground motions are generated and averaged
  • Curves are fit to match computed mean spectra
  • Resulting equations are used to develop a design response spectrum with desired probability of exceedence

Relationships for statistically derived spectra are available for western North America, eastern and central North America, and subduction zones. Be aware that the spectra for eastern and central North America and the Cascadia subduction zone are derived primarily from artificial ground motion records due to the lack of historical ground motion records in those areas. Most relationships are for psuedospectral acceleration, but several relationships for psuedospectral velocity are available as well. A table of relationships, including those for PGA, etc. is located in the attenuation relationships section of the notes, and interactive examples are available for all relationships listed.

Interactive Examples