Application of Dempster‐Shafer Theory for Interpretation of Seismic Parameters

Seismic design parameters are inherently imprecise and fuzzy. Formal models of inexact inferences are therefore highly relevant to the interpretation of such inexactly described seismic parameters. Application of such techniques becomes even more relevant if it is envisaged that, in the future, provisions for seismic design may be more effectively represented by encoding them as fuzzy expert systems. The linguistic representation of imprecise variables is presented. More importantly, how an evidence‐based scheme, the Dempster‐Shafer theory of evidence, can be used to infer conclusions about imprecisely stated problems is demonstrated. A set of seismic parameters, namely the seismic performance category (SPC), the seismic hazard exposure (SHE), and the seismic intensity (SI), are selected from a seismic design code. How the relationship between the three parameters can be “softened” is demonstrated using a linguistic representation; such a representation involves setting up conditional IF … THEN types of rules describing how different states of rule‐antecedents, SI and SHE, will lead to different states of a rule‐consequent, SPC. A frame of discernment (θ) is then defined which comprises several hypotheses about SPC. Thereafter evidence about SI and SHE is used to infer conclusions about SPC. The conclusions are represented by a combined degree of belief and plausibility in the hypotheses in θ.