Site-specific Fault Rupture Hazard Assessment--Fluorspar Area Fault Complex, Western Kentucky

Abstract

We evaluated post-Paleozoic sediments overlying a southerly projection of the Fluorspar area fault complex and coincident with an area of diffuse microseismicity for Quaternary deformation. Nearly 1 km of seismic reflection data were collected and interpreted for evidence of late Quaternary deformation. Five significant high-angle geophysical anomalies were interpreted to extend within approximately 7 m of the ground surface, near the upper limit of the seismic sampling. We subsequently collected 86 closely spaced, 9.1-m-deep, continuous cores above these anomalous features. We performed stratigraphic and chronological analyses on the cores to determine the presence or absence of structure above the geophysical anomalies and define the near-surface extent and age of deformation. Optical stimulated luminescence dates showed the sampled sediment age ranged between nearly 16 ka and greater than 125 ka. Interpretation of the resultant geologic cross-sections indicates identified stratigraphic anomalies were generally constrained to post-date a 53.6 to 75.5 ka loess deposit; however, no perceptible displacement was found at the base of younger loess dated between 16.6 and 23.5 ka.