Horizontal-to-Vertical Seismic Method (HVSR) Soundings in the Northern and Central Parts of the Tug Hill Glacial Aquifer, Jefferson and Oswego Counties, North Central New York

The U.S. Geological Survey, in cooperation with the New York State Department of Environmental Conservation, the Tug Hill Commission, the Jefferson County Soil and Water Conservation District, the Oswego County Soil and Water Conservation District, and the Tug Hill Land Trust collected horizontal-to-vertical seismic soundings at 139 locations in the Northern and Central parts of the Tug Hill Glacial Aquifer. The goal of the project was to help determine thickness of the unconsolidated deposits and depth to bedrock. The HVSR technique, commonly referred to as the passive-seismic method, is used to estimate the thickness of unconsolidated sediments and the depth to bedrock (Lane and others, 2008). The passive-seismic method uses a single, broad-band three-component (two horizontal and one vertical) seismometer to record ambient seismic noise. In areas that have a strong acoustic contrast between the bedrock and overlying sediments, the seismic noise induces resonance at frequencies that range from about 0.3 to 40 Hz. The ratio of the average horizontal-to-vertical spectrums produces a spectral-ratio curve with peaks at fundamental and higher-order resonance frequencies. The spectral ratio curve (the ratio of the averaged horizontal-to-vertical component spectrums) is used to determine the fundamental resonance frequency that can be used along with an average shear-wave velocity or a power-law regression equation to estimate sediment thickness and depth to bedrock (Lane and others, 2008; Brown and others, 2013; Fairchild and others, 2013; Chandler and others, 2014; and Johnson and Lane, 2016). The HVSR data presented in this data release were collected at each site in 30 minute intervals using a Tromino Model TEP-3C1 three-component seismometer. The data were processed with Grilla 2012 version 6.21 software to 1) remove anthropogenic noise, 2) convert the time-domain data to frequency domain, 3) compute and plot the spectral ratio curve, and 4) determine the resonance frequency. This data release presents the peaks of resonance frequency identified from the HVSR measurements. Also presented are reported depth-to-bedrock data for wells located at or near HVSR data-collection sites overlying the aquifer in Jefferson and Oswego counties. This exercise is for use in comparison of HVSR forward model depths to reported well depths. Raw and processed data for HVSR measurements are presented in the attached. The HVSR data-collection sites are designated by a county sequential numbering system (JHVSR33, OWHVSR50, etc. where ‘J’ and ‘OW’ indicate Jefferson and Oswego counties, respectively). 1Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

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  "geospatial"
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