The disadvantage of probabilistic seismic hazard analysis is that the concept of a “design earthquake” is lost; i.e. there is no single event that for design or retrofit. The relative contributions of the various sources to the total seismic hazard are determined as a function of their occurrence rates and their ground-motion potential. This study describes a method wherein a design earthquake can be obtained that accurately represents the uniform Fourier hazard spectrum from a PSHA. If different seismic sources dominate the hazard at different frequencies, then contributions to the hazard come from significantly different magnitudes, distances, and ε’s. In this case, a single design earthquake is not appropriate and it is necessary to represent design earthquake for short and long periods.
