Arthur D. Frankel Stephen C. Harmsen Charles S. Mueller Kathleen M. Haller Russel L. Wheller Robert L. Wesson Yuehua Zeng Oliver S. Boyd David M. Perkins Nicolas Luco Edward H. Field Christopher J. Wills Kenneth S. Rukstales Mark D. Petersen 2011 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/s 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 grid of points were contoured to produce the final representation of the seismic-hazard. These maps are intended to summarize the available quantitative information about seismic ground motion hazard for the conterminous United States from geologic and geophysical source. application/pdf 10.3133/sim3195 en U.S. Geological Survey Seismic-Hazard Maps for the Conterminous United States, 2008 reports