Quantifying and communicating uncertainty in seismic risk assessment

Modern seismic risk assessment strives to support risk mitigation by providing insight into the performance of civil infrastructure, including buildings, bridges and transportation and utility systems, subjected to severe earthquakes. A fully-coupled seismic risk or safety assessment of a structural system, and its accompanying analysis of uncertainty, provides estimates of the annual probability of exceeding pre-defined performance levels, defined either in terms of structural responses or more qualitatively defined damage states. All sources of uncertainty, both inherent and knowledge-based, should be included in risk assessment; however, the manner in which they are displayed depends on the preferences of the stakeholders and decision-makers. This paper illustrates how such uncertainties are propagated through a seismic risk assessment of steel frame building structures that are typical of regions of low-to-moderate seismicity in the Central and Eastern United States and explores some of the implications for risk-informed evaluation of civil infrastructure.