HVSR-ASSISTED MAPPING OF GLACIAL BURIED VALLEYS IN SOUTHWESTERN OHIO

Horizontal-to-vertical spectral ratio (HVSR) passive-seismic analysis has been incorporated as a key component of recent bedrock-topographic mapping activities in parts of Preble, Butler and Hamilton counties in southwestern Ohio. The HVSR analyses, calibrated to stations recorded at wells with known bedrock depths, have been used in conjunction with abundant depth-to-bedrock data from water well and geotechnical borehole drilling logs to generate updated bedrock topography and drift-thickness maps of the region. HVSR records have been instrumental in providing depth to bedrock estimates in areas with limited drilling records, as well as helping to identify previously unrecognized complexities in buried-valley deposits of the Four-Mile Creek, Seven-Mile Creek and Great Miami River drainages. In addition, study results indicate that HVSR depth-frequency calibration curves produce similar predicted depths for a given fundamental frequency regardless of valley-fill depositional components and landscape position. Collectively, the results of our mapping program indicate HVSR methodologies are a valuable predictive tool for determining the thickness of glacial-related valley-filling depositional sequences in areas proximal to the maximum extent of the Laurentide ice advance during the Last Glacial Maximum.