THREE-DIMENSIONAL GEOLOGIC MAP OF MCCRACKEN COUNTY, WESTERN KENTUCKY: PRELIMINARY RESULTS

Seismic hazards, such as amplification of earthquake ground motion, liquefaction, and earthquake-induced landslides, are affected by near-surface geologic conditions. The near-surface geology also affects groundwater flow and contaminant transport. McCracken County, in western Kentucky, is at risk to earthquake damage because of its proximity to the New Madrid Seismic Zone. Also, groundwater contamination at the Paducah Gaseous Diffusion Plant in the county is being cleaned up. A three-dimensional geologic map can provide useful information for the seismic-hazard assessment and groundwater clean-up.

The three-dimensional geology in McCracken County is being characterized by combining existing surface geologic maps with geophysical data, geotechnical data, and water-well data in a geographic information system (GIS). The first step in creating the three-dimensional map is to delineate subsurface boundaries of geologic materials using existing surface geologic maps, and to develop methods to integrate point data (stratigraphic control), line data (seismic profile), and areal data (digital geologic map) in three dimensions. The analysis of existing geophysical and geotechnical data, along with the collection of new geophysical data, will improve the geologic model and will help us to better describe relationships between lithologic materials and engineering properties. The three-dimensional geologic maps will be used to develop seismic-hazard maps, which will show potential for ground-motion amplification, liquefaction, and earthquake-induced slope failure in McCracken County.