We propose a new framework to facilitate dynamic assurance within a safety case approach by associating safety performance measurement with the core assurance artifacts of a safety case. The focus is mainly on the safety architecture, whose underlying risk assessment model gives the concrete link from safety measurement to operational risk. Using an aviation domain example of autonomous taxiing, we describe our approach to derive safety indicators and revise the risk assessment based on safety measurement. We then outline a notion of consistency between a collection of safety indicators and the safety case, as a formal basis for implementing the proposed framework in our tool, AdvoCATE.