14-15 September 2023 in Cambridge

Ellen Rathje

Applying the SSHAC Framework to Site Response Analysis for Critical Facilities

Abstract

Probabilistic seismic hazard analysis (PSHA) is the standard approach for developing earthquake ground motions for critical facilities because it account for the important sources of uncertainty and variability associated with the earthquake source and with ground motion prediction. The Senior Seismic Hazard Analysis Committee (SSHAC) process was initiated in 1997 by the US Nuclear Regulatory Committee to provide guidance on uncertainty and the use of experts in PSHA, and since then the SSHAC framework has been used for PSHA projects for critical facilities around the world. Site response analysis traditionally has been performed outside of the PSHA and, thus, the SSHAC process has not been utilized, despite the fact that significant uncertainties and judgments are associated with site response analysis. More recently, site response analysis has become part of the PSHA and guidance for applying the SSHAC process to site response analysis has been developed. This presentation will introduce the SSHAC process and its application to site response analysis in recent projects. The approach to developing site adjustment factors will be described, along with the main sources of epistemic uncertainty and aleatory variability. The logic tree approach to incorporate epistemic uncertainty will be demonstrated and examples provided.

Biography

Dr. Ellen M. Rathje is the Janet S. Cockrell Centennial Chair in Engineering in the Department of Civil, Architectural, and Environmental Engineering at the University of Texas at Austin (UT), and Senior Research Scientist at the UT Bureau of Economic Geology.  She has expertise in the areas of geotechnical earthquake engineering, engineering seismology, induced seismicity, field reconnaissance after earthquakes, and remote sensing.  She has participated in seismic hazard assessments and site response studies for nuclear facilities in South Africa, Taiwan, the United Kingdom, and the United States.  Dr. Rathje is the Principal Investigator for the DesignSafe-ci.org cyberinfrastructure for the NSF-funded Natural Hazards Engineering Research Infrastructure (NHERI).  She has been honored with various research awards, including the 2022 Ralph Peck Award from the ASCE Geo-Institute, the 2018 William B. Joyner Lecture Award from the Seismological Society of America and the Earthquake Engineering Research Institute, and the 2010 Huber Research Prize from the ASCE. She was elected Fellow of the American Society of Civil Engineers in 2016.