This study presents the results of a detailed Horizontal-to-vertical spectral ratio (HVSR) passive-seismic recording program in glacial filled-valley deposits in southwestern Ohio. Study goals were to evaluate the sensitivity of the HVSR method and best practices regarding field sampling techniques and data analysis. The study was conducted in the valley of Four Mile Creek near Oxford in Butler County, Ohio and includes >100 HVSR records taken at stations on an ~100-m grid spacing. The area investigated covers ~0.6 km2 across the entirety of the modern floodplain and into adjacent upland regions. Quaternary deposits, consisting of Holocene fluvial channel sand/gravel and overbank mud and Pleistocene glacial till, outwash sand/gravel, and lacustrine clay, are >70 m (>235 ft) thick but thin rapidly towards both valley margins where Ordovician bedrock is exposed. Logs from water wells, geotechnical boreholes and a core of the entire valley-fill assemblage permits subsurface calibration of HVSR frequency peaks. Study results indicate a systematic decrease in peak HVSR frequency from >30 Hz along the western valley outcrop exposures to ~2 Hz in the deepest part of the valley fill. The close spacing of the recording stations, in conjunction with detailed borehole data permits identification of key horizons in the valley fill deposits. Study results elucidate both the utility and limitations of the HVSR method to discern the thickness and lateral variability in heterogenous buried valley deposits.
Author(s): Eva Williams, Environmental Earth Science and Sustainability Major
Ben Shrider, Geology Major
Advisor(s): Brian Currie, Department of Geology & Environmental Earth Science
You must be logged in to post a comment.