Analysis of Bore-Hole Seismic Velocity Surveys at the Paducah Gaseous Diffusion Plant

Adequate seismic design of hazardous facilities depends on the ability to predict the influence of several layers of unconsolidated soils and sediments on ground motion at the free-surface during strong-motion earthquakes. Computer programs (such as SHAKE) have been developed to analyze ground motions at the free-surface. Such analyses are based on the physical properties of the soil column (all the layers of soil between the bedrock and ground surfaces). Physical properties include the thickness, density, and propagation velocities of artificially generated seismic waves through the soil in each layer. Shear and compressional wave velocities (V, and V_p, respectively) in unconsolidated layers of soil are commonly measured by a cross-hole seismic survey where an energy source and receivers are placed at the same elevation in adjacent holes. A down-hole seismic survey is an alternative to a cross-hole survey. In a down-hole survey two or more receivers (spaced a fixed distance apart on a cable) are lowed into a hole and an energy source is placed at the surface. A down-hole survey is occasionally used in the deeper part of the soil column where a cross-hole survey may be impractical. This paper presents an analysis of cross- and down-hole seismic surveys at the Paducah Gaseous Diffusion Plant (PGDP).