Using information theory concepts to compare alternative intensity measures for representing ground motion uncertainty

The seismic risk assessment of a structure in performance-based design may be significantly affected by the representation of ground motion uncertainty. The uncertainty in the ground motion is commonly represented by adopting a parameter or a vector of parameters known as the intensity measure (IM). In this work, a new measure, called a sufficiency measure, is derived based on information theory concepts, to quantify the suitability of one IM relative to another in representing ground motion uncertainty. Based on this measure, alternative IM’s can be compared in terms of the expected difference in information they provide about a designated structural response parameter. Several scalar IM’s are compared in terms of the amount of information they provide about the seismic response of an existing reinforced-concrete frame structure.