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

Fairchild, Gillian M.; Lane, John W., Jr.; Voytek, Emily B.; LeBlanc, Denis R.

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.

Genre:

USGS Numbered Series

ProdID:

70042759

Citation Author:

Fairchild, Gillian M.; Lane, John W., Jr.; Voytek, Emily B.; LeBlanc, Denis R.

Citation Contributing Office:

New England Water Science Center

Citation Datum:

North American Datum of 1983

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Citation Language:

English

Citation Larger Work Title:

Citation LatN:

41.791667

Citation LatS:

41.5

Citation LonE:

-70.375

Citation LonW:

-70.708333

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Citation Phsyical Description:

Pamphlet: iv, 17 p.; 1 Sheet: 48 x 36 inches; GIS materials; GIS instructions; 3 Tables; CD-ROM

Citation Projection:

Universal Transverse Mercator projection, Zone 19

Citation Public Comments:

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.

Citation Publisher:

U.S. Geological Survey

Citation Series:

Scientific Investigations Map

Citation Series Code:

SIM

Citation Series Number:

3233

Citation Search Results Text:

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; 2013; SIM; 3233; Fairchild, Gillian M.; Lane, John W., Jr.; Voytek, Emily B.; LeBlanc, Denis R.