Toxic Substances Hydrology Program

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 SpectralRatio Method 

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

Ashumet

Pond

-180

-140 -130

-130

-170

-140

-180

-190

-150

-150

-150

-170

-160

-160

-170

-180

-160

-150

-120

-120

-140

-190

-190

-170

-200

-180

-210

-220 -160

-150

-160

-170

-230

-240

-180

-170

-150

-160 -140

-190

-120

-130

-200

-170

-210

-160

-140

-180 -170

-140

-130

-150

-180

-170

-190

-190

-210

-230

-190

-160

-150

-140

-170

-170

-150

-170

-230

-220

-210-200

-260

-190-180

-170

-200

-220

-230

-240

-190

-210

-130

-180

-160

-190

-210

-220

-250

-260

-250-240

-230

Prepared in cooperation with the Army National Guard and the

Air Force Center for Engineering and the Environment

Scientific Investigations Map 3233

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2013

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Fairchild, G.M., Lane, J.W., Jr., Voytek, E.B., and LeBlanc, D.R., 2013, 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: U.S. Geological Survey Scientific Investigations Map 3233, 1 sheet, 

maps variously scaled, 17-p. pamphlet, on one CD–ROM. (Also available at http://pubs.usgs.gov/sim/3233.)
iii

Contents

Introduction.....................................................................................................................................................1

Study Design and Data Collection ..............................................................................................................3

Boring Logs and Seismic Refraction Surveys..................................................................................3

Analysis of Ambient Seismic Noise by the Horizontal-to-Vertical Spectral-Ratio Method .....3

Description of Data Sets .....................................................................................................................6

Bedrock Topography of Western Cape Cod, Massachusetts ................................................................6

Interpretation of Bedrock-Surface Topography ..............................................................................6

Comparison to Earlier Maps of the Bedrock Topography............................................................12

Summary........................................................................................................................................................12

References Cited..........................................................................................................................................12

Appendix........................................................................................................................................................15

Figures

1. Map showing location of study area near the Massachusetts Military Reservation, 

western Cape Cod, Massachusetts...........................................................................................2

2. Closeup photographs showing A, a single broadband, three-component 

seismometer, and B, the seismometer and data-collection system as typically 

deployed in the field .....................................................................................................................4

3. Example from site 00MW0584 of the graphical representation of the raw 

seismic data...................................................................................................................................5

4. Example of the Geopsy output graph of the fundamental resonance frequency 

determined by the spectral plot of the ratio of the averaged-horizontal to vertical 

components of the ambient seismic noise at site 00MW0584 ..............................................7

5. Topographic map of the bedrock surface beneath western Cape Cod as 

interpreted from horizontal-to-vertical spectral-ratio measurements, seismic 

refraction surveys, and geologic borings, western Cape Cod, Massachusetts ................8

6. Topographic map of the bedrock surface beneath the area near Snake Pond as 

interpreted mostly from geologic borings, western Cape Cod, Massachusetts................9

7. Topographic map of the bedrock surface beneath the area near Ashumet Pond as 

interpreted mostly from geologic borings, western Cape Cod, Massachusetts..............10

8. Topographic map of the bedrock surface beneath Cape Cod, Martha’s Vineyard, 

and Nantucket, Massachusetts ..............................................................................................11
iv

Conversion Factors and Datum

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Volume

gallon (gal) 3.785 liter (L) 

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27) 

and the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

List of Abbreviations

AFCEE Air Force Center for Engineering and the Environment (April 2007–present)

Air Force Center for Environmental Excellence (prior to April 2007)

ARNG Army National Guard

GPS global positioning system

HVSR horizontal-to-vertical spectral ratio

MMR Massachusetts Military Reservation

USGS U.S. Geological Survey
Bedrock Topography of Western Cape Cod, Massachusetts, 

Based on Bedrock Altitudes from Geologic Borings and 

Analysis of Ambient Seismic Noise by the Horizontal-toVertical Spectral-Ratio Method

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

Introduction

The bedrock surface of western Cape Cod defines the 

lower boundary of groundwater models that are used to predict 

the transport of groundwater contaminants originating on the 

Massachusetts Military Reservation (MMR). The bedrock 

surface is represented by a no-flow boundary in the models, 

and the topography of the surface plays an important role in 

determining the patterns of groundwater flow. The bedrock 

surface has been characterized in the past by using the results 

of seismic refraction surveys and geologic borings drilled to 

bedrock (Oldale, 1969; Air Force Center for Environmental 

Excellence (AFCEE), 2006). The horizontal-to-vertical 

spectral-ratio (HVSR) method, which is a passive seismic 

technique that uses an analysis of the horizontal and vertical 

components of ambient seismic noise (microtremors), has 

been introduced as a method to collect data on the depth to 

bedrock in a manner that is noninvasive and less expensive 

than drilling (Lane and others, 2008). These advantages are 

beneficial in an area such as western Cape Cod, where the 

land is occupied by residential and commercial properties, and 

depths to bedrock commonly exceed 200 feet (ft). The Toxic 

Substances Hydrology Program of the U.S. Geological Survey 

(USGS), working cooperatively with the Army National 

Guard (ARNG) and the Air Force Center for Engineering and 

the Environment (AFCEE), used the HVSR method during 

2008–10 to estimate bedrock depth in areas for which there 

was little information from drilling and to prepare a map of the 

altitude of the bedrock surface for western Cape Cod.

The purpose of this report is to present an updated 

topographic map of the bedrock surface beneath western Cape 

Cod, Massachusetts, for use in groundwater-flow models 

of the Sagamore lens of the Cape Cod aquifer. The bedrock 

surface was first mapped by Oldale in 1969, and the map 

was updated in 2006 by using bedrock altitudes estimated 

during the drilling by AFCEE and ARNG to identify the 

boundaries and sources of the contaminant plumes originating 

on the MMR (AFCEE, 2006). The borings are concentrated 

on the MMR and in the immediately surrounding area. This 

report updates the bedrock-surface map with new data points 

collected by using the HVSR method as well as data from 

additional borings drilled to bedrock since the 2006 map 

was prepared.

The area of the map presented in this report is on western 

Cape Cod (fig. 1) and includes the towns of Bourne (as 

far west as the Cape Cod Canal), Mashpee, Falmouth, and 

Sandwich, and the western portion of the town of Barnstable. 

The MMR covers the northwestern part of this area (fig. 1). 

The study area overlies unconsolidated glacial drift deposits 

that consist of medium-to-coarse-grained glaciofluvial 

sand and gravel outwash overlying fine-to-medium-grained 

glaciolacustrine sand and silt, with sandy moraines near 

the northern and western coasts. These deposits form the 

Sagamore lens of the Cape Cod aquifer, which underlies 

the entire area (Walter and Whealan, 2005). The underlying 

bedrock is primarily granodiorite (Oldale and Barlow, 1986; 

Oldale, 1992). The surficial topography of the study area is 

characterized by gently sloping areas on the outwash plains 

and hummocky terrain on the moraines.

The aquifer, which consists of the unconsolidated glacial 

sediments, is an unconfined system that is surrounded by 

saltwater. The water table in the unconfined glacial sediments 

reaches a maximum altitude of approximately 70 ft at 

the eastern boundary of the MMR (Walter and Whealan, 

2005). Several contaminant plumes originate on the MMR 

from historical defense-related activities (Massachusetts 

National Guard, 2012). The direction of movement of each 

contaminant plume depends on the position of the source of 

the contamination on the groundwater mound. Groundwater 

modeling has been used extensively to assist in predicting the 

fate and transport of the various contaminants originating on 

the MMR (AFCEE, 2006; Masterson and others, 1996; Walter 

and Masterson, 2003; Walter and LeBlanc, 2008).
2 Bedrock Topography of Western Cape Cod, Massachusetts

Ashumet

Pond

Snake

Pond

BUZZARDS BAY

CAPE COD

BAY

VINEYARD SOUND

NANTUCKET SOUND

CAPE COD CANAL

ATLANTIC

OCEAN

U.S. Geological Survey digital data

Universal Transverse Mercator projection

Zone 19, 1:24,000, 1991; State plane coordinate

system datum is the North American Datum

of 1983 (NAD 83) in meters

SANDWICH

MASHPEE

BOURNE

FALMOUTH

BARNSTABLE

5 MILES

5 KILOMETERS

0

0

41°42'30"

41°32'30"

70°27'30"

Massachusetts

Military

Reservation

41°30'

42°30'

73° 100,000

950,000

850,000

270,000

835,000

815,000

280,000

200,000 71°

0

0

50

50

MILES

KILOMETERS

MASSACHUSETTS

CAPE COD

70°37'30"

Figure 1. Location of study area near the Massachusetts Military Reservation, 

western Cape Cod, Massachusetts.
Study Design and Data Collection 3

Study Design and Data Collection

This effort included the compilation of geologic boring 

and seismic refraction survey data and the collection and 

analysis of the HVSR data for areas with little or no bedrock 

information. The HVSR method was applied at a total of 164 

sites on and near the MMR.

Boring Logs and Seismic Refraction Surveys

Geologic borings were drilled on and near the MMR in 

an effort to characterize the contaminant plumes originating 

on the MMR and obtain data on the hydrogeologic framework 

of the aquifer. The locations of 559 borings reported to have 

hit bedrock in the area are shown in figure 1–1 (appendix). 

These sites are concentrated near the contaminant plumes 

caused by chemical spills, fuel spills, leachate from landfills, 

and firing ranges used for artillery and small-arms practice 

(Massachusetts National Guard, 2012). The lithologic log and 

driller’s report for each of these locations were checked, and 

an estimated altitude of the bedrock surface was calculated 

from the reported depth to bedrock and land-surface altitude. 

A set of 463 additional borings that were drilled to at least 

200 feet below land surface but reportedly did not hit bedrock 

was also compiled (figure 1–1 in appendix). The boring logs 

were obtained from the environmental databases maintained 

by AFCEE and ARNG. 

Three seismic refraction surveys were done in Falmouth 

in 1958 (Oldale and Tuttle, 1964). These inline refraction 

traverses were made with a 12-channel portable refraction 

amplifier and oscillograph. Each survey was 1,100 feet long. 

These surveys recorded signals that are characteristic of 

geologic settings where unconsolidated sedimentary deposits 

overlie crystalline bedrock. Additional seismic refraction 

surveys were conducted on western Cape Cod in 1968 (Oldale, 

1969). Based on the data collected in each of these surveys, 

the average depth to bedrock was calculated over the length of 

the survey line.

Analysis of Ambient Seismic Noise by the 

Horizontal-to-Vertical Spectral-Ratio Method

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. A spectral analysis of 

the ambient seismic noise from the earth’s surface is used 

to determine the fundamental resonance frequency for the 

measurement site. Ambient seismic noise is composed of 

microtremors caused by ocean waves, wind, rainfall, and 

anthropogenic activities such as traffic and industry (Ibs-von 

Seht and Wohlenberg, 1999). The HVSR method works best at 

locations where the subsurface can be approximated by a twolayer model consisting of a layer of generally homogeneous, 

unconsolidated sediments overlying a consolidated bedrock 

layer. The HVSR method is effective in areas where there 

is a strong contrast in acoustic impedance between the 

sediment and bedrock (Lane and others, 2008; more detailed 

descriptions in Nakamura (1989) and Geopsy (2011)). 

Cape Cod’s geologic structure, with unconsolidated glacial 

sediments on top of granitic bedrock, produces a very distinct 

contrast in acoustic impedance at the sediment-bedrock 

interface; this structure makes Cape Cod an ideal setting in 

which to apply the HVSR method. 

At each measurement site, a single, broadband, threecomponent seismometer was used to record ambient seismic 

noise from the earth’s surface. The seismometer was placed 

directly on the ground or on a metal plate with spikes (fig. 

2A). The spikes on the bottom of seismometer or the metal 

plate were firmly driven into the ground to ensure that the 

seismometer was coupled well with the earth. A bullseye 

spirit level and north arrow built into the instrument and an 

external compass were used to level the instrument and align 

it with magnetic north. The seismometer was then connected 

to a laptop computer, a global positioning system (used for 

timing only), and a battery. The seismometer was covered with 

a weighted 5-gallon bucket to reduce interference from wind 

and weather (fig. 2B). Data collection was initiated by using 

the program Scream! (Guralp Systems, 2011) on the laptop 

computer. Data were collected for no less than 30 minutes at 

each location. To minimize noise, the equipment was set up 

approximately 30 feet from traffic when possible and where 

pedestrians, including those collecting the data, were not 

walking in the immediate area around the equipment; these 

disturbances would have created excessive noise that later 

would have had to be removed from the record. 

The raw seismic data were processed by using the 

program Geopsy version 2.7.0 (Geopsy, 2011). An example 

from site 00MW0584 of the graphical representation, 

produced by the Geopsy program, of the raw seismic data 

is shown in figure 3. The horizontal scale represents time, 

and the vertical scale represents the amplitudes of the data 

collected for seismic components in three perpendicular 

directions: vertical (Z), north-south (N), and east-west (E). 

The raw data were divided into time intervals 60 seconds 

long that overlap adjacent intervals by 30 seconds each. The 

small spikes in amplitude above the generally smooth traces 

were caused by high-amplitude noise disturbances such as the 

nearby passage of individual vehicles or pedestrians as data 

were being recorded. Data from these time intervals, which 

are not colored in figure 3, were removed prior to further 

data processing.

The fundamental resonance frequency at each site was 

determined by a spectral analysis of the horizontal and vertical 

components of the recorded ambient seismic noise. The 

amplitudes of the spectra of the vertical and two horizontal 

components of the microtremors for each of the 60-second 

time intervals were calculated by the Geopsy program. The 

average of the amplitudes of the horizontal components 

was divided by the vertical component, and this ratio (the 
4 Bedrock Topography of Western Cape Cod, Massachusetts

B

A

Seismometer 

under bucket

GPS

Battery

Computer

Figure 2. Closeup photographs showing A, a single broadband, three-component 

seismometer, and B, the seismometer and data-collection system as typically deployed 

in the field.
Study Design and Data Collection 

5

60 seconds

Vertical

North-SouthEast-West 

Figure 3. Example from site 00MW0584 of the graphical representation of the raw seismic data. Site location shown in figure 5.
6 Bedrock Topography of Western Cape Cod, Massachusetts

HVSR) was plotted as a function of frequency. The graphical 

output from the Geopsy software is shown in figure 4 for the 

example from site 00MW0584. Each colored line is the result 

of this analysis of the data from the 60-second time interval 

delineated by the similarly colored vertical band in figure 3. 

For this study, the processing parameters, which are defined 

and explained in detail in Geopsy (2011), included Konno 

and Ohmachi (1998) smoothing with a constant bandwidth of 

40, a cosine taper width of 5 percent, and a squared average 

for the horizontal components. An average HVSR spectral 

plot and spectral plots representing upper and lower limits 

of one standard deviation were calculated from the plots 

for the individual time intervals (fig. 4). The fundamental 

resonance frequency for the site is the frequency defined by 

the peak in the average HVSR plot. For the example from site 

00MW0584, the peak is located at a frequency of 1.06 Hertz 

(fig. 4). The Geopsy program automatically selects the peak 

in the processed data and determines the average resonance 

frequency and its standard deviation (fig. 4). The user also can 

manually select the peak if the peak selected by the program 

is unsatisfactory.

The depth to bedrock (or thickness of the unconsolidated 

sediments composing the top layer of the two-layer model) 

can be estimated from the fundamental resonance frequency 

by using the following relationship:

Z f = a b

r0 , (1)

where 

Z is the sediment thickness in ft, 

f

r0 is the fundamental resonance frequency 

in Hertz (s-1), and a (in ft•s) and b 

(dimensionless) are determined empirically 

from a nonlinear regression of data 

acquired at sites where Z is known 

from adjacent boreholes (Lane and 

others, 2008).

The constants a and b for this study (a = 297 ft•s and 

b = -1) were developed by Lane and others (U.S. Geological 

Survey, written commun., 2011) from a regression analysis of 

known bedrock depths from borings versus depths obtained 

by the HVSR method at 8 sites in this study area and 29 

additional sites on the glacial deposits of eastern Cape Cod 

and southeastern mainland Massachusetts. The 8 sites from 

this study area that were used to develop the empirical 

equation are highlighted in bold in tables 1–1 and 1–2 

(appendix). The estimated depth to bedrock for the example 

from site 00MW0584 is 279 ft. The altitude of the bedrock 

surface was obtained by subtracting the estimated depth to 

bedrock from the land-surface altitude. At site 00MW0584, 

where the land-surface altitude is 50 ft above NGVD 29, the 

resulting bedrock-surface altitude is 229 ft below NGVD 29.

A total of 164 sites were chosen for application of the 

HVSR method from areas for which little bedrock information 

from geologic borings and the seismic refraction surveys 

had been collected. These areas generally are near the coast 

in Bourne, Sandwich, Falmouth, Mashpee, and along the 

eastern edge of the map area in Barnstable. Sites with known 

land-surface altitudes were selected to allow the calculation 

of bedrock altitude from the estimated depth to bedrock. 

The HVSR data were collected during 2008–10 by several 

different seismometers. The measurements were repeated 

eight times at the Ashumet Pond public boat launch (site 

164 on fig. 1–1, appendix) and 15 times adjacent to building 

1146 (site 163 on fig. 1–1, appendix) on the MMR. Analysis 

of these repeated measurements was used to confirm that 

the instruments were collecting spatially and temporally 

consistent, comparable data.

Description of Data Sets

Several datasets were used to prepare the updated 

topographic map of the bedrock surface in this report. Data 

from sites where the bedrock surface was hit during drilling 

are given in table 1–1 (appendix). Seismic refraction data 

are documented in the reports by Oldale and Tuttle (1964) 

and Oldale (1969). Data from the HVSR method are given in 

table 1–2 (appendix). Finally, data on the maximum possible 

bedrock altitude at 463 sites where geologic borings were 

drilled to at least 200 ft below land surface but reportedly 

did not hit bedrock are given in table 1–3 (appendix). The 

locations of the borings and HVSR measurement sites are 

shown in figure 1–1 (appendix).

Bedrock Topography of Western 

Cape Cod, Massachusetts

A topographic map of the bedrock surface beneath 

western Cape Cod was prepared by using data from the 

geologic borings, seismic refraction surveys, and HVSR 

measurements. The map was prepared by manually 

contouring the bedrock altitudes estimated from the datacollection methods.

Interpretation of Bedrock-Surface Topography

The bedrock-surface altitudes from the HVSR survey, 

seismic refraction surveys, and geologic borings that 

reportedly hit bedrock were plotted on a map of western Cape 

Cod and hand-contoured with a 25-ft contour interval (fig. 

5). This interval is within the range of estimated uncertainty 

of about 10 percent of the depth to bedrock (20–30 ft) in the 

bedrock-surface altitudes estimated for much of the area from 

the HVSR method. Bedrock-surface altitudes in two smaller 

areas near Snake Pond (fig. 6) and Ashumet Pond (fig. 7) with 

closely spaced data points were contoured with a 10-ft contour 

interval. The bedrock-surface altitudes in these two areas were 

measured mostly from borings; the altitudes from the borings 

were estimated to have a range of uncertainty of about 5 ft. 
Bedrock Topography of Western Cape Cod, Massachusetts 7

Ratio of averaged-horizontal to vertical amplitudes (HVSR) Mean Upper and lower limits of one standard deviation EXPLANATION

Frequency in Hertz (Hz) 

Peak at 1.06 Hz 

Figure 4. Example of the Geopsy output graph of the fundamental resonance frequency determined by the spectral plot of the ratio of the averaged-horizontal to vertical components of the ambient seismic noise at site 00MW0584. Site location shown in figure 5.
8 Bedrock Topography of Western Cape Cod, Massachusetts

0 15,000 30,000 FEET

0 4,000 8,000 METERS

850,000 900,000

225,000

300,000

70°40' 70°30'

41°45'

41°30'

Cape Cod Canal

Base from USGS and MassGIS sources, North American Datum of 1927 (NAD 27) 

Altitudes relative to the National Geodetic Vertical Datum of 1929 (NGVD 29)

-250

-250

-250

-200

-250

-225

-225 -250

-200

-200

-200

-200

-225

-225 -225

-200

-200

-200

-200

-225

-225

-250

-275 -300

-300

-275

-250

-250

-275

-275

-250

-175

-200

-175

-275

-175

-175

-150

-125

-175

-175

-125

-200

-200

-125

-125

-125

-150

-150

-150

-175

-175

-175

-125

-150

-300

-300

-375

-400

-425

-425

-325

-325

-325

-375

-350

-350

-350

-275

-350

-275

-275

-275

-225

-225

-225

-250

-275

-300

-300

-225

-225

-200

-200

-175

-175

-150

-125

-125

-150

-175

-125

-125

-150

-175

-175

-150

-150

-150

-175

-200

-225

-250

-250

-225

-175

-275 -275

-200

-150

-125

-175

-200

-150

-125

-150

-150

-100

-75

-275

-250

-225

-200

-375

-400

-200

-225

-250

-150

-125

-350

-175

-100 -200

-125

-150

-200

-250 -200

EXPLANATION

Altitude of bedrock surface

High -50 feet

Low -450 feet

Altitude contours—relative to

 sea level, interval is 25 feet, 

 datum is NGVD 29

Town boundary

Massachusetts Military Reservation boundary 

Pond shoreline

Ocean coastline

Location of well 00MW0584 

 on eastern shore of Johns Pond

00MW0584 

SANDWICH

MASHPEE

BOURNE

FALMOUTH

MASSACHUSETTS

MILITARY

RESERVATION

Woods Hole

BUZZARDS BAY

CAPE COD

BAY

VINEYARD 

SOUND

NANTUCKET

 SOUND

BARNSTABLE

Figure 5. Topographic map of the bedrock surface beneath western Cape Cod as interpreted from horizontalto-vertical spectral-ratio measurements, seismic refraction surveys, and geologic borings, western Cape Cod, 

Massachusetts. Location of map shown in figure 1.
Bedrock Topography of Western Cape Cod, Massachusetts 9

The contours were initially drawn by adhering strictly to 

the estimated altitudes, but were then adjusted slightly where 

appropriate within the range of uncertainty described above to 

smooth the surface near anomalous features based on single 

data points. Finally, the contours were checked for consistency 

with the maximum possible altitudes at the deep borings 

that did not hit bedrock; the contours required only minimal 

adjustments during this final check. 

862,500 70°32' 870,000 70°30'

250,000

260,000

41°43'

41°42'

41°41' Snake 

Pond

-140

-130

-120

-160

-150

-160

-140

-170

-170

-150

-120

-150

-140

-170

-160

-170

-130

-160

-170

-160

-120

-110

-100

-150

-140

-140

-160

-130

-130

-130

-170

-160

-170

-150

-140

-150

0 2,000 4,000 FEET

0 500 1,000 METERS

EXPLANATION

Altitude of bedrock surface

High -100 feet

Low -185 feet

Altitude contours—relative to

 sea level, interval is 10 feet, 

 datum is NGVD 29

Pond shoreline

Figure 6. Topographic map of the bedrock surface beneath the area near Snake Pond as interpreted mostly from geologic 

borings, western Cape Cod, Massachusetts. Location of map shown in figure 5.
10 Bedrock Topography of Western Cape Cod, Massachusetts -160 EXPLANATION High -120 feet Low -280 feet

0 2,000 4,000 FEET0

Altitude of bedrock surface

Altitude contours—relative to sea level, interval is 10 feet,  datum is NGVD 29

Pond shoreline

500 1,000 METERS

850,000 860,000 70°32' 70°34'

240,000230,000

41°40'41°38'

Ashumet

Pond

-180

-140

-130

-130

-170

-140

-180

-190

-150

-150

-150

-170

-160

-160

-170

-180

-160

-150

-120

-120

-140

-190

-190

-170 -200

-180

-210

-220

-160

-150

-160

-170

-230

-240

-180

-170-160 -150-140

-190

-120

-130

-200

-170

-210

-160

-140

-170

-180

-140

-130

-150

-180

-170

-190

-190

-210

-230

-190

-150

-140

-160

-170

-150

-170

-170

-230

-220

-210

-200

-260

-190-180-170

-200

-220

-230

-240

-190

-210

-130

-180

-160

-190

-220

-210

-260

-250

-250

-240

-230

Figure 7. Topographic map of the bedrock surface beneath the area near Ashumet Pond as interpreted mostly from geologic borings, western Cape Cod, Massachusetts. Location of map shown in figure 5.
Bedrock Topography of Western Cape Cod, Massachusetts 11

Figure 8. Topographic map of the bedrock surface beneath Cape Cod, Martha’s Vineyard, and Nantucket, Massachusetts (from 

Oldale, 1969).
12 Bedrock Topography of Western Cape Cod, Massachusetts

Comparison to Earlier Maps of the 

Bedrock Topography

The interpreted representation of the bedrock surface in 

figure 5 is similar in its general features to Oldale’s 1969 map 

(fig. 8) and AFCEE’s 2006 map. In all three maps, the bedrock 

surface generally slopes downward to the southeast from the 

Cape Cod Canal toward Nantucket Sound. The maps similarly 

show lobes of shallower bedrock extending to the east toward 

Barnstable and to the south toward Woods Hole. The bedrock 

surface is at least 47 ft below NGVD 29 (sea level) throughout 

the mapped area and therefore does not crop out at the 

land surface.

The bedrock surface presented in this report shows 

more topographic detail than the earlier maps owing to the 

increase in the quantity of data available for use in drawing the 

contours. The general trends in altitude shown on the smallscale map (fig. 5) may reflect preglacial drainage patterns 

in the bedrock surface. The large-scale maps (figs. 6 and 7), 

however, show a surface whose altitude varies considerably 

over a small area. The same variability could be characteristic 

of the entire study area, but more data would be needed to 

test this hypothesis. Small-scale variations, including closed 

depressions in the bedrock surface, are consistent with a 

glacially eroded bedrock surface (B.D. Stone, U.S. Geological 

Survey, oral commun., 2011).

Summary

The HVSR method was used successfully to obtain 

estimates of the bedrock-surface altitude for western Cape 

Cod, Massachusetts, in areas for which altitudes from 

borings drilled to bedrock or from seismic refraction surveys 

had not been estimated. The HVSR method was effective 

in 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 to create a spatially distributed dataset for the study 

area 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 previous maps by Oldale (1969) and AFCEE (2006). The 

surface also has complex small-scale topography, as was also 

shown in the AFCEE (2006) map. The updated map reflects 

the data available through October 2012 from borings to 

bedrock and better spatial resolution from the HVSR data 

in areas outside the MMR for which less information on the 

bedrock altitudes had been collected.

References Cited

Air Force Center for Environmental Excellence (AFCEE), 

2006, Massachusetts Military Reservation Plume Response 

Program, final Chemical Spill-23 wellfield design report: 

Jacobs Engineering Group, Inc., A4P–J23–35BC06VB–

M23–0003, variously paged. 

Geopsy, 2011, Geopsy Project: Geopsy, accessed February 24, 

2011, at http://www.geopsy.org/.

Guralp Systems, 2011, Scream! Software for Windows and 

Linux: Guralp Systems, accessed February 24, 2011, at 

http://www.guralp.com/category/software.

Ibs-von Seht, Malte, and Wohlenberg, Jürgen, 1999, 

Microtremor measurements used to map thickness of 

soft sediments: Bulletin of the Seismological Society of 

America, v. 89, no. 1, p. 250–259.

Konno, Katsuaki, and Ohmachi, Tatsuo, 1998, Ground-motion 

characteristics estimated from spectral ratio between 

horizontal and vertical components of microtremor[s]: 

Bulletin of the Seismological Society of America, v. 88, 

no. 1, p. 228–241.

Lane, J.W., Jr., White, E.A., Steele, G.V., and Cannia, J.C., 

2008, Estimation of bedrock depth using the horizontalto-vertical (H/V) ambient-noise seismic method, in

Symposium on the Application of Geophysics to 

Engineering and Environmental Problems, April 6–10, 

2008, Philadelphia, Penn., Proceedings: Denver, Colo., 

Environmental and Engineering Geophysical Society, 13 p.

Massachusetts National Guard, 2012, Massachusetts Military 

Reservation, Cape Cod, Massachusetts—Environmental 

overview, accessed April 30, 2012, at http://states.ng.mil/

sites/MA/MMR/environ-overview.htm.

Masterson, J.P., Walter, D.A., and Savoie, Jennifer, 1996, Use 

of particle tracking to improve numerical model calibration 

and to analyze groundwater flow and contaminant 

migration, Massachusetts Military Reservation, western 

Cape Cod, Massachusetts: U.S. Geological Survey WaterSupply Paper 2482, 50 p.

Nakamura, Y., 1989, A method for dynamic characteristics 

estimations of subsurface using microtremors on the ground 

surface: Quarterly Report, Railway Technical Research 

Institute, Japan, v. 30, p. 25–33.
References Cited 13

Oldale, R.N., 1969, Seismic investigations on Cape Cod, 

Martha’s Vineyard, and Nantucket, Massachusetts, and a 

topographic map of the basement surface from Cape Cod 

Bay to the Islands, in Geological Survey Research 1969, 

Chapter B, Scientific notes and summaries of investigations 

in geology, hydrology, and related fields: U.S. Geological 

Survey Professional Paper 650–B, p. B122–B127.

Oldale, R.N., and Barlow, R.A., 1986, Geologic map of Cape 

Cod and the Islands, Massachusetts: U.S. Geological Survey 

Miscellaneous Investigations Series Map I–1763, 1 sheet, 

scale 1:100,000.

Oldale, R.N., and Tuttle, C.R., 1964, Seismic investigations on 

Cape Cod, Massachusetts, article 145 in Geological Survey 

Research 1963, Short papers in geology and hydrology, 

Articles 122–172: U.S. Geological Survey Professional 

Paper 475–D, p. D118–D122. 

Oldale, R.N., 1992, Cape Cod and the Islands—The geologic 

story: Orleans, Mass., Parnassus Imprints, 208 p.

Walter, D.A., and LeBlanc, D.R., 2008, Use of inversemodeling methods to improve groundwater-model 

calibration and evaluate model-prediction uncertainty, 

Camp Edwards, Cape Cod, Massachusetts: U.S. Geological 

Survey Scientific Investigations Report 2007–5257, 49 p.

Walter, D.A., and Masterson, J.P., 2003, Simulation of 

advective flow under steady-state and transient recharge 

conditions, Camp Edwards, Massachusetts Military 

Reservation, Cape Cod, Massachusetts: U.S. Geological 

Survey Water-Resources Investigations Report 03–4053, 

51 p.

Walter, D.A., and Whealan, A.T., 2005, Simulated water 

sources and effects of pumping on surface and ground 

water, Sagamore and Monomoy flow lenses, Cape 

Cod, Massachusetts: U.S. Geological Survey Scientific 

Investigations Report 2004–5181, 85 p.
This page has been left blank intentionally.
Appendix
16 Bedrock Topography of Western Cape Cod, Massachusetts

EXPLANATION

B344

94 Horizontal-to-vertical spectral-ratio

 measurement site—location and 

 identifier (table 1-2)

With PDF viewer software, open layers menu

 and turn each layer on and off by clicking 

 the eye symbol

M372

Geologic boring that hit bedrock—location

 and identifier (table 1-1)

Geologic boring that did not hit 

 bedrock—location and identifier (table 1-3)

0 15,000 30,000 FEET

0 4,000 8,000 METERS

MMR 

boundary

B9

B8

B7

B6

B5

B4

B2

B1

B98 B99

B97 B96

B91 B94

B88

B87

B82 B81

B79 B80

B78B77

B75 B74

B68 B67

B50

B43

B31

B20 B19

B18

B13 B12

B11

B559

B557 B558

B556

B550 B549

B547 B548

B545

B544

B543

B542

B540

B538 B539

B535

B534

B533

B532

B530

B528 B529 B527

B526

B522

B521

B520

B519

B517

B511

B509

B504

B503

B500

B498

B497

B492

B487

B480

B477 B476

B472

B466

B456

B454 B455

B450

B449

B447

B444

B443

B437

B427

B425

B424

B423

B420

B416 B419

B406 B415

B377

B376

B364

B361

B356

B349

B345

B344

B343

B340

B339

B338

B336

B333

B332

B330

B329

B323

B321

B320

B318

B316

B315

B313

B310

B308

B300

B295 B296

B294

B292

B291

B281

B275

B257 B268 B274

B253

B246

B241

B233 B240

B232 B231

B216 B204

B203

B201

B200 B199

B192

B188

B186

B185

B184

B183

B181

B178

B168 B170

B166

B164

B158

B145

B144

B142

B141

B105

M9

M8 M7

M6

M5

M4

M3

M2

M1

M99 M98

M97

M9 M96 5

M91 M92

M89 M90

M88 M87

M84

M83

M81

M78 M77

M74

M7 M72 M70 1

M56

M55

M54

M52

M46

M44

M19

M18

M12

M10

M463

M462

M460 M461

M459

M458

M457

M456

M452 M450

M449

M448

M445

M444

M443

M442

M441

M435

M4 M434 33

M431 M427

M426

M423

M421

M416

M409

M395

M394

M3 M391 M392 90

M388

M379

M372

M371

M365

M363

M362

M361

M360

M359

M356

M355

M352

M346

M342

M341

M339

M337 M336

M3 M335 34

M330

M328

M327 M326

M325

M324 M314

M274

M262

M252 M255

M250

M218

M215 M210

M208

M203 M201

M193 M194

M185

M151

M150

M148

M144 M145

M143

M140

M127

M118

M117

M111

M109

9

8

7

6

5

4 3

2

1

99

98

97

96

95

94

93

92

91

90

89

88

87

86

85

84

83

82

81

80

79

78

77

76

75

74

73

72

71

70

69

68

67

66

65

64

63 62

61

60 59

58

57

56

55

54

5253

51

50

49

48

47

46

45

44

43

42

41

39

38

37

35

34

33

31 32 30 28

27

26

25

24

23 22

21

20

19 18

17

13

11 164

163

163

162

161

160

159

158

157

156

155

154

153

152

150

149

148

147

146

145

144

143

142

141

140 139

138

137 136

135 134

133

132

131

130

129

128

127

126

125

124

123 122 121 119

118

116 117

115

114

113

112 111

110

108

107

106

105

104

103

102

101

100

70°40' 850,000 70°30' 900,000

225,000

300,000

41°45'

41°30'

Base from USGS and MassGIS sources, North American Datum of 1927 (NAD 27)

Northings and eastings in state plane meters, sites plotted as of October 2012

This map, as layered PDF, manufactured to

allow user to turn map layers on and off

Figure 1–1. Locations of geologic borings and horizontal-to-vertical spectral-ratio measurements used to prepare the topographic 

map of the bedrock surface, western Cape Cod, Massachusetts. (Click here for PDF of fig. 1–1)
Tables 17

Table 1–1. Locations, altitudes of land and bedrock surfaces, and depths below land surface to bedrock for geologic borings where 

bedrock was hit during drilling, western Cape Cod, Massachusetts. (Click here)

Table 1–2. Locations, altitudes of land surface, estimated altitudes and depths below land surface of the bedrock surface, and 

fundamental resonance frequencies at locations of horizontal-to-vertical spectral-ratio (HVSR) measurements, western Cape Cod, 

Massachusetts. (Click here)

Table 1–3. Locations, altitudes of land surface, maximum altitudes of the bedrock surface, and depths below land surface for 

geologic borings where bedrock was not hit and drilling was extended to at least 200 feet below land surface, western Cape Cod,

Massachusetts. (Click here)
This page has been left blank intentionally.