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2023 Update of the USGS National Seismic Hazard Model for the Conterminous US

The U.S. Geological Survey’s National Seismic Hazard Model Project (NSHMP) plans to next update the National Seismic Hazard Model (NSHM) for the conterminous U.S. in 2023. The timing of the update will allow for (1) two years of development, (2) stakeholder feedback early and often (e.g., kick-off workshop in January 2021 and regional workshops throughout the update process), (3) one year for external review of the NSHM documentation and publication and (4) coordination with the next update of the NEHRP Recommended Seismic Provisions for New Buildings and Other Structures (and the 2028 ASCE 7 Standard and the 2023 International Building Code). The timeline for the 2023 NSHM update is posted on our website (https://www.usgs.gov/natural-hazards/earthquake-hazards/hazards).

The previous update in 2018 was focused on updating central and eastern U.S. (CEUS) ground motion models (GMMs) and incorporating basin amplifications in four urban areas in the western U.S. (WUS). The 2023 update will focus on updating the WUS source model (e.g., new faults) and subduction-zone GMMs (i.e., NGA-Subduction). Additional updates may include improved Atlantic and Gulf Coast site-effect models, the Uniform California Earthquake Rupture Forecast (UCERF) with updated catalogs and other logic tree modifications, GMMs derived from physics-based 3D simulations, non-ergodic aleatory ground motion uncertainty, additional basin-effect models for urban areas in the WUS, updated geodetic models, new magnitude-area scaling relations and improved treatment of the WUS-CEUS attenuation boundary. The NSHMP requests that the earthquake hazards community bring to our attention new source and ground motion data or models that could be included in the 2023 NSHM. The deadline for publication of external data or models to be considered by the NSHMP for this update is December 31, 2020.

Presenting Author: Allison M. Shumway

Additional Authors