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Bedrock topography of western Cape Cod, Massachusetts, based on bedrock altitudes from geologic borings and analysis of ambient seismic noise by the horizontal-to-vertical spectral-ratio method

Scientific Investigations Map 3233
Prepared in cooperation with the Army National Guard and the Air Forice Center for Engineering and the Environment. This report is available online and in CD-ROM format, please contact the Office Chief for ordering information.
By: , , , and 
https://doi.org/10.3133/sim3233

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Abstract

This report presents a topographic map of the bedrock surface beneath western Cape Cod, Massachusetts, that was prepared for use in groundwater-flow models of the Sagamore lens of the Cape Cod aquifer. The bedrock surface of western Cape Cod had been characterized previously through seismic refraction surveys and borings drilled to bedrock. The borings were mostly on and near the Massachusetts Military Reservation (MMR). The bedrock surface was first mapped by Oldale (1969), and mapping was updated in 2006 by the Air Force Center for Environmental Excellence (AFCEE, 2006). This report updates the bedrock-surface map with new data points collected by using a passive seismic technique based on the horizontal-to-vertical spectral ratio (HVSR) of ambient seismic noise (Lane and others, 2008) and from borings drilled to bedrock since the 2006 map was prepared. The HVSR method is based on a relationship between the resonance frequency of ambient seismic noise as measured at land surface and the thickness of the unconsolidated sediments that overlie consolidated bedrock. The HVSR method was shown by Lane and others (2008) to be an effective method for determining sediment thickness on Cape Cod owing to the distinct difference in the acoustic impedance between the sediments and the underlying bedrock. The HVSR data for 164 sites were combined with data from 559 borings to bedrock in the study area to create a spatially distributed dataset that was manually contoured to prepare a topographic map of the bedrock surface. The interpreted bedrock surface generally slopes downward to the southeast as was shown on the earlier maps by Oldale (1969) and AFCEE (2006). The surface also has complex small-scale topography characteristic of a glacially eroded surface. More information about the methods used to prepare the map is given in the pamphlet that accompanies this plate.

Study Area

Publication type Report
Publication Subtype USGS Numbered Series
Title Bedrock topography of western Cape Cod, Massachusetts, based on bedrock altitudes from geologic borings and analysis of ambient seismic noise by the horizontal-to-vertical spectral-ratio method
Series title Scientific Investigations Map
Series number 3233
DOI 10.3133/sim3233
Year Published 2013
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) New England Water Science Center
Description Pamphlet: iv, 17 p.; 1 Sheet: 48 x 36 inches; GIS materials; GIS instructions; 3 Tables; CD-ROM
Country United States
State Massachusetts
County Bourne;Falmouth;Mashper;Sandwich
Other Geospatial Cape Cod
Datum North American Datum of 1983
Projection Universal Transverse Mercator projection, Zone 19
Scale 24000
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details