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Publications > Johnson and Lane, 2016
Carole D. Johnson, U.S. Geological Survey, Storrs-Mansfield, Connecticut
John W. Lane, Jr., U.S. Geological Survey, Storrs-Mansfield, Connecticut
Determining sediment thickness and delineating bedrock topography are important for assessing groundwater availability and characterizing contamination sites. In recent years, the horizontal-to-vertical spectral ratio (HVSR) seismic method has emerged as a non-invasive, cost-effective approach for estimating the thickness of unconsolidated sediments above bedrock. Using a three-component seismometer, this method uses the ratio of the average horizontal- and vertical-component amplitude spectrums to produce a spectral ratio curve with a peak at the fundamental resonance frequency. The HVSR method produces clear and repeatable resonance frequency peaks when there is a sharp contrast (>2:1) in acoustic impedance at the sediment/bedrock boundary. Given the resonant frequency, sediment thickness can be determined either by (1) using an estimate of average local sediment shear-wave velocity or by (2) application of a power-law regression equation developed from resonance frequency observations at sites with a range of known depths to bedrock. Two frequently asked questions about the HVSR method are (1) how accurate are the sediment thickness estimates? and (2) how much do sediment thickness/bedrock depth estimates change when using different published regression equations? This paper compares and contrasts different approaches for generating HVSR depth estimates, through analysis of HVSR data acquired in the vicinity of Tylerville, Connecticut, USA.
Download the complete article [460KB PDF].
Final copy as submitted to Environmental and Engineering Geophysical Society for publication as: Johnson, C.D. and Lane, J.W., Jr., 2016, Statistical comparison of methods for estimating sediment thickness from horizontal-to-vertical spectral ratio (HVSR) seismic methods: An example from Tylerville, Connecticut, USA, in Symposium on the Application of Geophysics to Engineering and Environmental Problems, March 20-24, 2016, Denver, Colorado, Proceedings: Denver, Colorado, Environmental and Engineering Geophysical Society, 7 p.
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