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Updated Mmax Distributions for Seismic Hazard Analyses of Nuclear Facilities in the Central and Eastern US

Description: 

This study examines changes in maximum magnitude (Mmax) characterization by analyzing an up-to-date earthquake catalog for the Central and Eastern US (CEUS) region. The objective is to assess whether the expanded catalog data warrants an update of the Mmax distribution of the CEUS Seismic Source Characterization (SSC) model for nuclear facilities (NUREG-2115). The main interest is at lower annual exceedance frequencies, which are of relevance in probabilistic seismic hazard analysis studies concerning critical infrastructure. The CEUS-SSC model was developed following a rigorous Senior Seismic Hazard Analysis Committee Level 3 process and relied on a catalog complete through 2008. In 2015 EPRI published recalculated Mmax distributions for 8 zones to correct an error in the original estimates. We compiled an updated catalog by adding earthquakes that occurred in the CEUS study region since January 1, 2009, for which there is a seismic moment. We note that many earthquakes in the updated catalog occurred in Texas and Oklahoma and are likely associated with human activities.

The calculation of Mmax follows 3 main steps: (1) application of the Johnston et al. (1994) Bayesian approach with a set of prior distributions obtained from groupings of stable continental regions with similar crust; (2) application of the Kijko (2004) approach; and (3) assessment of the relative weights to assign to each method. We find that when earthquakes occurred since 2008 are added to the catalog, there is a general tendency for a slight downward shift in the Mmax distribution for many of the CEUS-SSC source zones. Using three demonstration sites as example locations, we find that the updated Mmax distributions generally lead to small decreases in hazard rates at low annual frequencies of exceedance computed with the CEUS-SSC earthquake rate parameters.

Session: Advancing Seismic Hazard and Risk Assessment through Multi-Disciplinary Approaches [Poster]

Type: Poster

Date: 4/15/2026

Presentation Time: 08:00 AM (local time)

Presenting Author: Shreyasvi Chandrasekhar

Student Presenter: No

Invited Presentation: 

Poster Number: 40

Authors