Recommendations for Probabilistic Seismic Hazard Analysis: Guidance on Uncertainty and Use of Experts: Appendices (NUREG/CR-6372, Volume 2)

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Publication Information

Manuscript Completed: April 1997
Date Published:
April 1997

Prepared by:
Senior Seismic Hazard Analysis Committee (SSHAC)
R.J. Budnitz (Chairman), G. Apostolakis, D.M. Boore, L.S. Cluff,
K.J. Coppersmith, C.A. Cornell, P.A. Morris

Under Contract to:
Lawrence Livermore National Laboratory
Livermore, California 94550

Prepared for:
Division of Engineering Technology
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Engineering and Operations Support Group
Office of Defense Programs
U.S. Department of Energy
19901 Germantown Road
Germantown, Maryland 20874-1290

Electric Power Research Institute
3412 Hillview Avenue
Palo Alto, California 94304-1395

NRC Job Code L2503

Availability Notice


Probabilistic Seismic Hazard Analysis (PSHA) is a methodology that estimates the likelihood that various levels of earthquake-caused ground motion will be exceeded at a given location in a given future time period. Due to large uncertainties in all the geosciences data and in their modeling, multiple model interpretations are often possible. This leads to disagreement among experts, which in the past has led to disagreement on the selection of ground motion for design at a given site.

In order to review the present state-of-the-art and improve on the overall stability of the PSHA process, the U.S. Nuclear Regulatory Commission (NRC), the U.S. Department of Energy (DOE), and the Electric Power Research Institute (EPRI) co-sponsored a project to provide methodological guidance on how to perform a PSHA.

The project has been carried out by a seven-member Senior Seismic Hazard Analysis Committee (SSHAC) supported by a large number other experts.

The SSHAC reviewed past studies, including the Lawrence Livermore National Laboratory and the EPRI landmark PSHA studies of the 1980s and examined ways to improve on the present state-of-the-art.

The Committee's most important conclusion is that differences in PSHA results are due to procedural rather than technical differences. Thus, in addition to providing a detailed documentation on state-of-the-art elements of a PSHA, this report provides a series of procedural recommendations.

The role of experts is analyzed in detail. Two entities are formally definied—the Technical Integrator (TI) and the Technical Facilitator Integrator (TFI)—to account for the various levels of complexity in the technical issues and different levels of efforts needed in a given study.

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