New Tools to Determine Seismic Hazard and Other Seismic Parameters for the United States

The U. S. Geological Survey (USGS) has completed new probabilistic seismic hazard maps for the United States. The maps depict peak horizontal ground acceleration, and 0.2, 0.3, and 1.0 sec response spectral acceleration values for 10%, 5%, and 2% probabilities of exceedance in 50 years (corresponding to approximate return times of 500, 1000, and 2500 years, respectively). The maps for the 0.2 sec and 1.0 sec response spectral acceleration with a 2% probability exceedance in 50 years, modified by engineering judgement, are the basis for seismic design maps developed for the 1997 NEHRP Recommended Provisions for Seismic Regulations for New Buildings. The USGS team preparing the new maps made a concentrated effort to make as much of the data used available via our Internet Website. This includes documentation, input data, output data, and computer code used to calculate the maps. In addition two CDROMs have been prepared - one for the probabilistic maps and one for the seismic design maps. Paper maps are also available.