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Probabilistic seismic hazard analysis (PSHA) is a widely used method for seismic hazard assessment. PSHA predicts a relationship, called the seismic hazard curve, between the maximum ground motion or response spectra and the annual frequency of exceedance (return period). Generally, the smaller the annual frequency of exceedance, meaning the longer the return period, the larger the ground motion— seismic hazard—PSHA will predict, and vice versa. PSHA is the most widely used method for assessing seismic hazards for input into various aspects of public and financial policy.

Site conditions at 37 locations in Paducah, Kentucky, and the surrounding area were modeled using seismic refraction and reflection data to determine site response to a suite of Canadian strong-motion records and a hypothetical central United States earthquake. The seismic data, integrated with local borehole information, indicated that depths to bedrock range from less than 300 to more than 500 ft. The site-response analysis shows that the study area can be subdivided into three zones and the highest spectral amplifications are associated with thick alluvial and lake-bed deposits. The magnitude of spectral ratios ranges from less than five to more than 20 times, and dynamic site periods range from 0.7 to 1.5 sec. Although this study relates directly to the Paducah area, the methods and types of data collected are applicable for other Upper Mississippi Embayment communities for land-use planning and the design of critical structures.

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