Seismic design requirements for critical facilities normally require the development and application of a uniform hazard spectrum having a specified return period. For a soil site, hazard results are often evaluated for bedrock level and soil surface.
This paper introduces a method for the evaluation of the seismic risk at the site of an engineering project. The results are in terms of a ground motion parameter (such as peak acceleration) versus average return period. The method incorporates the influence of all potential sources of earthquakes and the average activity rates assigned to them.
Ground-motion prediction (attenuation) models predict the probability distributions of spectral acceleration values for a specified earthquake event. In this article a large number of strong ground motions are used to empirically estimate these correlations, and nonlinear regression is used to develop approximate analytical equations for their evaluation.