Transient Electromagnetics, Passive Seismic, and Borehole Electromagnetics, Gamma, and Nuclear Magnetic Resonance Methods to Characterize Glacial Sediments in East Falmouth, Massachusetts, Near Nantucket Sound

Passive seismic horizontal-to-vertical spectral ratio (HVSR) methods were used to estimate the depth of the unconsolidated deposits over bedrock. The HVSR method uses a three-component seismometer to measure the vertical and two horizontal components of ambient seismic noise. Seismic noise in the range of ~0.1 to 1 Hertz (Hz) is caused by ocean waves, large regional storms, and tectonic sources. A resonance frequency (f0) is induced in the unconsolidated deposits when there is a substantial contrast (> 2:1) in shear-wave acoustic impedance between the overburden and the bedrock. The f0 is determined from the analysis of the spectral ratio of the horizontal and vertical components of the seismic data. The thickness of the overburden can be related to the f0. In general, lower f0 relates to thicker sediments, and higher f0 relates to relatively thinner overburden.