USGS National Seismic Hazard Model

USGS National Seismic Hazard Model
Name	USGS National Seismic Hazard Model
Jurisdiction	United States
Agency	United States Geological Survey
Formed	1996

USGS National Seismic Hazard Model The USGS National Seismic Hazard Model provides probabilistic estimates of ground shaking across the United States to support Federal Emergency Management Agency, National Institutes of Health, Department of Transportation, California Department of Water Resources, and City of Los Angeles planning, building code, insurance rate setting, and research. The model integrates earthquake catalogs, fault studies, and seismic monitoring networks such as Advanced National Seismic System, Parkfield Experiment, Hayward Fault investigations, and collaborations with institutions like California Institute of Technology, University of California, Berkeley, Massachusetts Institute of Technology, Stanford University, and Southern California Earthquake Center.

Overview

The model produces maps and hazard curves that quantify peak ground acceleration and spectral acceleration for specified probabilities used by International Code Council, American Society of Civil Engineers, National Institute of Standards and Technology, New Zealand Society for Earthquake Engineering, and state agencies. Outputs inform seismic design provisions referenced by International Building Code, ASCE 7, California Building Code, Oregon Department of Transportation, and Nevada Seismic Safety Commission. Stakeholders such as insurance companies, real estate developers, Los Angeles County, San Francisco Bay Area Rapid Transit District, and Port Authority of New York and New Jersey use the model to allocate resources and set priorities.

Development and Methodology

Development began through collaborations among United States Geological Survey, Southern California Earthquake Center, Geological Survey of Canada, New Zealand Council for Geoscience, National Research Council, and university consortia. Methodology combines probabilistic seismic hazard analysis workflows similar to those used by Cornell University researchers and incorporates ground motion prediction equations developed by investigators at Pacific Earthquake Engineering Research Center, Lawrence Livermore National Laboratory, U.S. Army Corps of Engineers, Electric Power Research Institute, and Oak Ridge National Laboratory. The modeling framework uses logic trees, epistemic uncertainty representation, and site amplification factors informed by studies at Evergreen Basin, Cascadia Subduction Zone, San Andreas Fault, Wasatch Fault, and New Madrid Seismic Zone.

Data Sources and Models

Primary earthquake occurrence data derive from catalogs maintained by International Seismological Centre, National Earthquake Information Center, Northern California Earthquake Data Center, Southern California Earthquake Data Center, and regional networks like Pacific Northwest Seismic Network. Fault geometry and slip rates use paleoseismology results from Paleoseismology of the San Andreas Fault, trenching studies at Pallett Creek, and GPS deformation fields from Plate Boundary Observatory, Scripps Institution of Oceanography, Harvard University, and Jet Propulsion Laboratory. Ground motion models draw on empirical studies by Frankel et al., Boore and Atkinson, Campbell and Bozorgnia, and other contributors affiliated with Seismological Society of America, European Seismological Commission, and American Geophysical Union.

Applications and Use

Practitioners apply the model in seismic hazard assessments for nuclear power plants regulated by the Nuclear Regulatory Commission, lifeline design for Federal Highway Administration projects, retrofits of structures overseen by Port of Seattle, and urban resilience planning in municipalities like San Francisco, Los Angeles, Anchorage, Salt Lake City, and Phoenix. Researchers use model outputs in tsunami forecasting collaborations with National Oceanic and Atmospheric Administration, landslide inventories with United States Forest Service, and seismic risk modeling for Munich Re and Swiss Re. Engineering firms such as Arup, AECOM, Bechtel, and Jacobs Engineering integrate hazard curves into site-specific response spectra for structural analysis.

Updates and Version History

Major releases occurred in 1996, 2002, 2008, 2014, and 2023 with technical contributions from Working Group on California Earthquake Probabilities, Collaboratory for the Study of Earthquake Predictability, Participation of Pacific Northwest Seismic Network, and international peer review including members from United Kingdom Geological Survey and Geoscience Australia. Each update incorporated revised seismicity rates, new fault mapping from agencies like California Geological Survey and Nevada Bureau of Mines and Geology, updated ground motion models by researchers at University of Southern California and University of California, Los Angeles, and expanded coverage for offshore regions such as Gulf of Alaska and Aleutian Islands. Versioning is documented in technical reports prepared by the United States Geological Survey in cooperation with National Science Foundation-funded teams.

Limitations and Criticism

Criticism centers on epistemic uncertainty in long-term recurrence estimates for complex systems like the Cascadia Subduction Zone, epistemic choices in logic trees debated by members of Seismological Society of America and National Research Council, and limited resolution for induced seismicity from hydraulic fracturing and wastewater injection in regions such as Oklahoma, Kansas, and Northern Texas. Stakeholders including local governments and utility companies have called for greater transparency in weighting schemes and incorporation of non-Poissonian clustering models advanced by researchers at Columbia University and Brown University. Additional limitations include uneven seismic instrumentation density across territories such as Puerto Rico and U.S. Virgin Islands compared with continental regions, prompting collaborative efforts with Caribbean Geological Institute and University of Puerto Rico.

Category:Seismology