SITE EFFECTS AT A VERTICAL ACCELEROMETER ARRAY NEAR PADUCAH, KENTUCKY

The downhole vertical accelerometer array VSAP near Paducah, KY, consi sts of three-component accelerometers at the surface, the top of the M cNairy Formation (-41 m), and the top of the Paleozoic bedrock (-99 m) . The array is at the northern end of the Mississippi Embayment, and i t was installed to verify the ground-motion modeling for the site, ass uming a significant earthquake in the New Madrid Seismic Zone. Acceler ograms from 4.2 and 2.0 m(b) earthquakes were used to check aspects of the modeling pertaining to linear behavior of the soil column, and to review the soil column models derived by drilling and geotechnical me thods and through the use of high-resolution P- and SH-wave seismic re fraction and reflection techniques. Results of the study indicate that for the linear case the soil column models derived by the two techniq ues are equivalent, and that the most important boundary in the soil c olumn, with respect to amplification of the ground motions, is the int erface between the limestone bedrock and soil.