Horizontal-to-Vertical Spectral Ratio Soundings and Depth-to-Bedrock Data for New York City and Long Island, NY

From March 2019 to September 2020, the U.S. Geological Survey, in cooperation with the New York City Department of Design and Construction and the New York State Department of Environmental Conservation, collected horizontal-to-vertical seismic (HVSR) surveys at 140 locations in New York, Bronx, Queens, Nassau, and Suffolk counties 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 other, 2013; Chandler and others, 2014; and Johnson and Lane, 2016).  

The HVSR data presented in this data release was collected at each site for 20 minutes using a Tromino Model TEP-3C1 three-component seismometer. The data was 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 resonance frequency peaks identified from the HVSR measurements. Also presented are reported depth-to-bedrock data for wells located at or near HVSR data-collection sites in Suffolk, Nassau, and Queens counties (Long Island) for use in comparison of HVSR forward model depths to reported well depths. Raw and processed HVSR data for each HVSR measurement are presented in the attached. The HVSR data-collection sites are designated by a county sequential numbering system for each of the five counties (NYHVSR8, NYHVSR9, etc. where NY indicates New York County, Bx indicates Bronx County, Qn indicates Queens County, Sf indicates Suffolk County, and Ns indicates Nassau County). 

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