The complexity of tectonic environments and the limited data available for seismic source and ground motion characterization make the use of a significant level of expert judgment in seismic hazard assessment studies unavoidable. In the mid-90s the Nuclear Regulatory Commission, the U.S. Department of Energy, and the Electric Power Research Institute sponsored a study to develop recommendations for how studies incorporating the use of expert assessments should be conducted in the future. The Senior Seismic Hazard Analysis Committee (SSHAC) developed a structured, multi-level assessment process (the "SSHAC process") described in NUREG/CR-6372 that has since been used for numerous natural hazard studies and is recommended in NRC Regulatory Guide 1.208 for the development of new models to be used in probabilistic seismic hazard analyses.