The 2018 Update of the U.S. National Seismic Hazard Model defines the potential for earthquake ground shaking for various probability levels across the conterminous United States and is applied in seismic provisions of building codes, insurance rate structures, risk assessments, and other public policy. The updated model represents an assessment of the best available science in earthquake hazards and incorporates new findings on earthquake ground shaking, seismicity, and long-period amplification over deep sedimentary basins. The new model represents an update of the seismic hazard model; previous versions were developed in 1996, 2002, 2008, and 2014.
The output from the National Seismic Hazard Model is a suite of seismic hazard curves calculated on a grid of latitude/longitude locations across the conterminous United States that describe the annual frequency of exceeding a set of ground motions. Hazard curves and probabilistic hazard data and maps for VS30 equal to 760 m/s and 260 m/s (NEHRP site class B/C and D), for 0.2, 1.0, and 5.0 second periods, as well as PGA, are available for download below, in the Child Items. Maps depict probabilistic ground motions with a 2 percent, 5 percent, and 10 percent probability of exceedance in 50 years. Spectral accelerations are calculated for 5 percent damped linear elastic oscillators. Additional maps and data portraying the chance of damaging earthquake shaking, probabilistic Modified Mercalli Intensity, and the seismicity catalog used in the hazard model are also available for download.
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