USE OF TECHNICAL EXPERT PANELS - APPLICATIONS TO PROBABILISTIC SEISMIC HAZARD ANALYSIS

Probabilistic Seismic Hazard,Analysis (PSHA) is a methodology that est imates the likelihood that various levels of earthquake-caused ground motions will be exceeded at a given location in a given future time pe riod. Due to large uncertainties in all of the geosciences data and in their modeling, multiple model interpretations are often possible. Th is leads to disagreements among the experts, which in the past has led to disagreement on the selection of a ground motion for design at a g iven site. This paper reports on a project, co-sponsored by the U.S. N uclear Regulatory Commission, the U.S. Department of Energy, and the E lectric Power Research Institute, that was undertaken to review the st ate-of-the-art and improve on the overall stability of the PSHA proces s, by providing methodological guidance or! how to perform a PSHA. The project reviewed past studies and examined ways to improve on the pre sent state-of-the-art. In analyzing past PSHA studies, the most import ant conclusion is that differences in PSHA results are commonly due to process rather than technical differences. Thus, the project concentr ated heavily on developing process recommendations, especially on the use of multiple experts, and this paper reports on those process recom mendations. The problem of facilitating and integrating the judgments of a diverse group of experts is analyzed in detail. The authors belie ve that the concepts and process principles apply just as well to non- earthquake fields such as volcanic hazard, flood risk, nuclear-plant s afety, and climate change.