SEISMIC HAZARD MAPPING IN THE LOUISVILLE METROPOLITAN AREA, KENTUCKY

Seismic hazards associated with local geology, such as ground-motion amplification, liquefaction, and earthquake-induced slope failure, can result in great damage during earthquakes. Many densely populated areas along the Ohio River, such as metropolitan Louisville are unlain by thick and soft soils that are prone to amplification and liquefaction. These two hazards can be assessed if soil properties and groundwater table are known. Important properties such as depth to bedrock, standard penetration test (SPT), and shear-wave velocity are being characterized using surface geologic, water well, geotechnical, and geophysical data. The ground-motion amplification hazard is assessed based on the average shear-wave velocity of the top 30-m (100-ft) of soil (NEHRP 1994 methodology). Two steps are required to properly evaluate the liquefaction hazard. In the first step, the Youd and Perkins liquefaction susceptibility criteria are applied, based on depositional environments and ages: this identifies the soil units that have liquefaction potential. The next step is to further evaluate the soil units that meet the liquefaction susceptibility criteria, using soil engineering properties, depth to water-table, and potential ground-motion level. These maps can be used by emergency managers, land-use planners, and general public for seismic hazard mitigation.