Probabilistic seismic-hazard maps were prepared for the conterminous United States
portraying peak horizontal acceleration and horizontal spectral response
acceleration for 0.2- and 1.0-second periods with probabilities of exceedance
of 10 percent in 50 years and 2 percent in 50 years. All of the maps
were prepared by combining the hazard derived from spatially smoothed
historic seismicity with the hazard from fault-specific sources. The
acceleration values contoured are the random horizontal component. The
reference site condition is firm rock, defined as having an average shear-wave
velocity of 760 m/sec in the top 30 meters corresponding to the boundary
between NEHRP (National Earthquake Hazards Reduction program) site classes
B and C.
This data set represents the results of calculations of hazard curves for a grid of points with a spacing of 0.05 degrees in latitude and longitude. The points were contoured to produce the final representation of the seismic hazard.
|Posted May 2005
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