Abstract:

These data are high-resolution seismic reflection profile data of the seafloor offshore of Massachusetts, from Nahant 

to Gloucester.  Approximately 1,175 kms of seismic reflection profile data were collected using a Knudsen 320b chirp system

Data were processed using SIOSEIS (Scripps Institute of Oceanography) and Seismic Unix (Colorado School of Mines) to produce segy files 

and jpg images of the profiles.  Data were then imported into Landmark SeisWorks, an interactive computer system where horizons were 

interpreted and digitized to calculate depth to reflectors below the seafloor.  Interpreted depth to reflectors were calculated, 

exported every 5 shots, and then imported to ArcGIS for interpolation into a 50-m raster grid.  These data were used to generate a 

sediment isopach map, which shows the total thickness of sediment that overlies bedrock

Purpose:

These data were collected under a cooperative agreement with the Massachusetts Office of Coastal Zone Management 

(CZM) and the U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center. High resolution bathymetry, 

backscatter intensity, and seismic profile data were collected over 127 km² area covering a portion of the South Essex Ocean Sanctuary 

to characterize the surface and subsurface of the seafloor for regional geologic framework investigations.

Bathymetric data were collected during two different surveys. Survey RAFA03007 
began Monday, 22 Sep 2003 (JD267) and ended on Tuesday, 14 Oct 2003 (JD287). RAFA04002 began 17 Apr 2004 (JD 108) and ended on 2 May 

2004 (JD123).

Currentness reference:

ground condition

Use constraints:

Data are not intended for navigational use.

These data should not be used at resolutions for which it is not intended.

Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution.  Please recognize 

the U.S. Geological Survey (USGS) as the source of this information.

Address:

384 Woods Hole Rd.

Logical consistency report:

These data have not been quantitatively compared to previous hydrographic data, although they generally agree with 

qualitative comparison of published NOAA charts.

Vertical positional accuracy report:

Seismic data are not corrected for tides. The bedrock depth (sediment thickness) is calculated as the distance 

between the bedrock and the seafloor from interpretation of seismic reflection profiles.

Process description:

Seismic profiles were interpreted in Landmark software. Each seismic profile was reviewed and acoustic reflectors 

were digitized.

Process description:

Interpreted horizons were exported as x,y,z (depth to reflector) and then imported to ArcGIS as point feature class 

for interpolation using Geostatistical Analyst.

Process description:

Shot data with depth to reflector was interpolated using ArcGIS Geostatistical Analyst with the following parameters

Selected Method: Universal Kriging
    Output: Prediction Map

Number of datasets currently in use: 1

Number of Points: 326304

Order of Trend: Const (Estimated by Global Polynomial Interpolation)

Semivariogram/Covariance:
    Model: 69.118*Spherical(1625.9)+31.914*Nugget
    Error modeling:
            Microstructure: 31.914 (100%)
            Measurement error: 0 (0%)

Searching Neighborhood:
    Neighbors to Include: 9 or at least 4 for each angular sector
    Searching Ellipse:
        Angle: 0
        Major Semiaxis: 1625.9
        Minor Semiaxis: 162

Dataset overview:

Depth to bedrock in ESRI GRID format.  Data values represent thickness (in meters) of sediment between seafloor and 

the bedrock

Address:

384 Woods Hole Rd.

Distribution liability:

Although this data set has been used by the U.S. Geological Survey (USGS), no warranty, expressed or implied, is made 

by the USGS as to the accuracy of the data and/or related materials.  The act of distribution shall not constitute any such warranty, 

and no responsibility is assumed by the USGS in the use of these data or related materials.

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

Format specification:

ESRI Raster GRID format

Address:

384 Woods Hole Rd.

bedrock_depth- Nahant to Gloucester, Depth to Bedrock
	Data format: Raster Dataset - ESRI GRID File or table name: bedrock_depth Coordinate system: Universal Transverse Mercator Theme keywords: U.S. Geological Survey, USGS, Coastal and Marine Geology Program, CMGP, Woods Hole Science Center, WHSC, Seafloor, Marine Geology, Seismic Reflection Profile, Knudsen, ArcGIS Raster, field activity serial number RAFA03007, field activity serial number RAFA04002, depth to bedrock, bedrock, isopach, oceans and estuaries, elevation, imageryBaseMapsEarthCover
Abstract: These data are high-resolution seismic reflection profile data of the seafloor offshore of Massachusetts, from Nahant to Gloucester. Approximately 1,175 kms of seismic reflection profile data were collected using a Knudsen 320b chirp system Data were processed using SIOSEIS (Scripps Institute of Oceanography) and Seismic Unix (Colorado School of Mines) to produce segy files and jpg images of the profiles. Data were then imported into Landmark SeisWorks, an interactive computer system where horizons were interpreted and digitized to calculate depth to reflectors below the seafloor. Interpreted depth to reflectors were calculated, exported every 5 shots, and then imported to ArcGIS for interpolation into a 50-m raster grid. These data were used to generate a sediment isopach map, which shows the total thickness of sediment that overlies bedrock

FGDC and ESRI Metadata: