Arnell S. Forde
Nancy T. DeWitt
Jake J. Fredericks
Jennifer L. Miselis
20180116
Archive of Chirp Subbottom Profile Data Collected in 2015 from the Northern Chandeleur Islands, Louisiana
multimedia presentation
U.S. Geological Survey Data Release
doi:10.5066/F7668C5C
St. Petersburg, Florida
U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center
https://doi.org/10.5066/F7668C5C
Arnell S. Forde
Nancy T. DeWitt
Jake J. Fredericks
Jennifer L. Miselis
20180117
Chirp Subbottom Profile Data Collected in 2015 from the Northern Chandeleur Islands, Louisiana
U.S. Geological Survey Data Series
1077
Reston, Virginia
U.S. Geological Survey
https://doi.org/10.3133/ds1077
From September 14 to 28, 2015, the U.S. Geological Survey (USGS) conducted a geophysical survey to investigate the geologic controls on barrier island evolution and medium-term and interannual sediment transport along the sand berm constructed in 2011 (offshore, at the northern end of the Chandeleur Islands, Louisiana) as mitigation of the Deepwater Horizon oil spill. This investigation is part of a broader USGS project, which seeks to better understand barrier island evolution over medium time scales (months to years). This publication serves as an archive of unprocessed, digital chirp subbottom data, survey trackline map, navigation files, geographic information system (GIS) data, and formal Federal Geographic Data Committee (FGDC) metadata. Processed subbottom profile images are also provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG Y revision 0 format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU).
These data are available for viewing using GeoMapApp (http://www.geomapapp.org/) and Virtual Ocean (http://www.virtualocean.org/) multi-platform open source software. In addition, the SEG Y files can be downloaded from the USGS Coastal and Marine Geoscience Data System (http://cmgds.marine.usgs.gov).
To archive all digital chirp subbottom profile data and associated files collected during Field Activity Number 2015-331-FA. Additional survey and data details are available from the U.S. Geological Survey Coastal and Marine Geoscience Data System (CMGDS) at, https://cmgds.marine.usgs.gov/fan_info.php?fan=2015-331-FA.
All Chirp systems use a signal of continuously varying frequency; the system used during this survey produces high-resolution, shallow-penetration (typically less than 75-milliseconds [ms]) profile images of sub-seafloor stratigraphy. The towfish contains a transducer that transmits and receives acoustic energy and is typically towed 1–2 meters (m) below the sea's surface. As transmitted acoustic energy intersects density boundaries, such as the seafloor or sub-surface sediment layers, energy is reflected toward the transducer, received, and recorded by a PC-based seismic acquisition system. This process is repeated at regular intervals (for example, 0.125 seconds [s]) and returned energy is recorded for a specific duration (for example, 50 ms). In this way, a two-dimensional (2D) vertical image of the shallow geologic structure beneath the towfish is produced.
The seismic source utilized during 2015-331-FA consisted of an EdgeTech SB-424 towfish running Discover version 3.51 acquisition software and towed approximately 3.6 m in front (port side) of the Global Positioning System (GPS) antenna. The data were acquired using a frequency sweep of 4–20 kilohertz (kHz), a 43 kHz sample frequency, and recording lengths that ranged between approximately 67 and 242 ms. Based on survey speeds of 3.5 knots, the shot spacing was approximately 0.450 m.
The binary portion of the unprocessed seismic data is stored in SEG Y rev. 0, IBM float format, which is a standard digital format that can be read and manipulated by most seismic processing software packages; the first 3,200 bytes of the file header are in American Standard Code for Information Interchange (ASCII) format instead of Extended Binary Coded Decimal Interchange Code (EBCDIC) format. The SEG Y formatted trace files have a .sgy extension and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2010). The printable profiles provided are chirp subbottom profile images that were processed using SU software. Survey Field Activity Collection System (FACS) and geophysical logs are also provided as supplemental information in the download file, 2015-331-FA_logs.zip.
20150914
20150928
ground condition
None planned
-88.877667
-88.832981
30.072044
30.015653
USGS Metadata Identifier
USGS:038cad80-d0e8-4328-bc44-b1a1ed999a5c
ISO 19115 Topic Category
geoscientificInformation
oceans
USGS Thesaurus
sub-bottom profiling
marine geology
geology
coastal processes
Data Categories for Marine Planning
distributions
physical habitats and geomorphology
Marine Realms Information Bank (MRIB) Keywords
seismic reflection profiling
None
Seismic reflection
Chirp
Society of Exploration Geophysicists
SEG Y
Barrier Island Mapping
2015-331-FA
Geographic Names Information System (GNIS) Content
United States of America
Louisiana
Gulf of Mexico
Chandeleur Islands
None. These data are held in the public domain.
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey requests to be acknowledged as originator of the data in future products or derivative research.
Arnell S. Forde
U.S. Geological Survey
Geologist
mailing and physical
600 4th Street South
Saint Petersburg
FL
33701
USA
(727) 502-8000
aforde@usgs.gov
Funding and (or) support for this study was provided by the USGS Coastal and Marine Geology Program. The authors thank Kyle Kelso of the USGS SPCMSC for his assistance in data collection and piloting the research vessel (R/V) Sallenger. This document was improved by reviews from Noreen Buster and and Xan Fredericks of the USGS - St. Petersburg, Florida.
Environment as of Metadata Creation: Microsoft Windows 7 Version 6.1 (Build 7601) Service Pack 1; Environmental Systems Research Institute (Esri) ArcGIS 10.3.1.4959
Barry, K.M., Cavers, D.A., and Kneale, C.W.
1975
Recommended standards for digital tape formats
Geophysics
v. 40, no. 2
pages 344-352
http://www.seg.org/publications/tech-stand/
Cohen, J.K., and Stockwell, J.W., Jr., CWP/SU
2010
Seismic Un*x Release No. 44: An open source software package for seismic research and processing
Golden, Colorado
Center for Wave Phenomena, Colorado School of Mines
http://www.cwp.mines.edu/cwpcodes/
The validity or accuracy of marine subbottom profiles is highly qualitative and dependent on equipment and operating condition variables. Visual inspection of the images rendered from the data did not show major anomalies.
These datasets are from one field activity with consistent instrument calibrations.
A total of 57 seismic lines were collected during this survey. These data are collected along 2D tracklines and are therefore inherently incomplete.
Differential global positioning system (DGPS) correction was obtained through the Marinestar high precision (HP) broadcast subscription from Fugro, Inc., which has a manufacturer's stated horizontal accuracy of 10 centimeters (cm). To ensure consistent spacing between survey lines (for example, 5 m in the nearshore and 10 m for offshore lines), pre-determined trackline locations were imported into Hypack 15.0.1.1 navigation software and followed during seismic data collection. As the subbottom data were acquired, vessel position was recorded in real-time kinematic mode via the CodaOctopus F190R+ Precision Attitude and Positioning System, which integrates the Marinestar position data with measured vessel heave, pitch, and roll. Positions from the CodaOctopus F190R+ inertial aided navigation system (IANS) were recorded and written to seismic trace headers in latitude and longitude coordinates (World Geodetic System of 1984, WGS84) every 1 second (s). The approximate 4-m offset between the chirp shot and ship's GPS was not accounted for during acquisition, nor have the ASCII navigation files and trackline map been corrected to reflect the offset.
These data are not to be used for bathymetry. Two-way travel (TWT) times shown on the printable profile images are relative to the chirp towfish position, not to the sea surface.
Chirp processing: The SEG Y data were processed with Seismic Unix (Release 44) software to produce gained Graphics Interchange Format (GIF) images of the subbottom profiles included in this data release. A representative chirp data processing sequence consisted of (1) removing navigation data for each shot and converting the SEG Y file to SU format, (2) applying automatic gain control, (3) generating a PostScript image of the traces, and (4) converting the PostScript image to a GIF image. For additional SU processing and script details, please refer to Data Series 1077 (Forde and others, 2018).
SEG Y
2016
SEG Y.gif
Arnell S. Forde
U.S. Geological Survey
Geologist
mailing and physical address
600 4th Street South
St. Petersburg
FL
33701
(727) 502-8000
aforde@usgs.gov
Navigation processing: Location data were extracted from the SEG Y headers using Seismic Unix software and output as ASCII text files; PROJ.4.7.0 (http://trac.osgeo.org/proj/) software was used to project WGS84 latitude and longitude coordinates to Universal Transverse Mercator (UTM) northings and eastings (WGS84, Zone 16, meters). Raw navigation files for each seismic line, saved by Julian Day (JD) and line number, were concatenated into comma-delimited text files for use with Esri ArcGIS software. The final output files are as follows: (1) 2015-331-FA.txt contains unique shotpoint positions (along each line) for the entire survey, (2) s2015-331-FA.txt includes the 1,000-shot-interval locations that were generated to correlate shot locations on the trackline map with evenly spaced 1,000-shot index markers along the top of the printable profile images, and (3) 2015-331-FA_s has the start-of-line locations for each trackline. The concatenated, comma-delimited text files were later imported into ArcGIS and saved as either a point or polyline file (in Esri's shapefile format) for use in the map document (.mxd) included in this archive.
JD*.txt
2016
2015-331-FA.txt
s2015-331-FA.txt
2015-331-FA_s.txt
Arnell S. Forde
U.S. Geological Survey
Geologist
mailing and physical address
600 4th Street South
St. Petersburg
FL
33701
(727) 502-8000
aforde@usgs.gov
Trackline map creation: 2015-331-FA_location.mxd was created with Esri ArcGIS 10.3.1 software. The survey navigation file, 2015-331-FA.txt, was imported into ArcMap 10.3.1 and processed using the ArcScript "Points to Lines" to create a line shapefile of the cruise tracklines called 2015-331-FA_trkln. The 1,000-shot-interval file and the start-of-line file were imported into ArcMap and saved as point shapefiles 2015-331-FA_shots and 2015-331-FA_sol, respectively. The ArcGIS files included in this release are unprojected (geographic coordinates, WGS84). Please refer to the shapefile metadata and readme file, included in 2015-331-FA_arc.zip, for detailed information about the geospatial files provided in this data release.
2015-331-FA.txt
s2015-331-FA.txt
2015-331-FA_s.txt
2016
2015-331-FA_trkln.shp
2015-331-FA_shots.shp
2015-331-FA_sol.shp
Arnell S. Forde
U.S. Geological Survey
Geologist
mailing and physical address
600 4th Street South
St. Petersburg
FL
33701
(727) 502-8000
aforde@usgs.gov
Added keywords section with USGS persistent identifier as theme keyword.
20201013
U.S. Geological Survey
VeeAnn A. Cross
Marine Geologist
Mailing and Physical
384 Woods Hole Road
Woods Hole
MA
02543-1598
508-548-8700 x2251
508-457-2310
vatnipp@usgs.gov
Point
0.0197884765
0.0227336944
Decimal Degrees
World Geodetic System of 1984
WGS 1984
6378137.0
298.257223563
2015-331-FA.txt, s2015-331-FA.txt, 2015-331-FA_s.txt
Shotpoint navigation files
SEG Y headers http://www.seg.org/publications/tech-stand.
UTMX
UTM-X coordinate (Zone 16)
Universal Transverse Mercator Coordinate System
319211.339
323123.872
meters
UTMY
UTM-Y coordinate (Zone 16)
Universal Transverse Mercator Coordinate System
3322594.357
3328251.18
meters
Line
Trackline number
U.S. Geological Survey
The naming convention used for each subbottom line is as follows: JD###_LxFy, where '###' is the integer assigned on the Julian Day (JD) of data collection, 'L' is an abbreviation of line and precedes the line number, 'x' is a 1- or 2-digit number representing a specific trackline number, 'F' is an abbreviation of file, and 'y' is a number representing a new line if recording was prematurely terminated or reran for quality or acquisition problems. If a trackline exceeded the file size limit/maximum shotpoint number (as determined by the acquisition software, Discover v. 3.51) the filename was appended with sequentially increasing numbers such as .001, .002, etc.
Shot
Shotpoint number
U.S. Geological Survey
1
16000
Lon
Longitude (decimal degrees)
World Geodetic System 1984 Geographic Coordinate System
-88.877667
-88.832981
decimal degrees
Lat
Latitude (decimal degrees)
World Geodetic System 1984 Geographic Coordinate System
30.015653
30.072044
decimal degrees
YEAR
Year
U.S. Geological Survey
2015
2015
DOY:HR:MIN:SEC
Day of year:hour:minute:second
U.S. Geological Survey
Day of year, hour, minute and second of data acquisition
Binary data file: Seismic trace data are available as binary files in SEG Y format. These files have a .sgy extension and range in size from 2.5 to 123 MB. These data are included in the download file, 2015-331-FA_segy.zip, and can also be found by going to http://cmgds.marine.usgs.gov. The SEG Y rev. 0 format (Barry and others, 1975) presented here consists of the following: a 3,600-byte reel identification header, with the first 3,200 bytes consisting of an ASCII header block followed by a 400-byte binary header block, both of which include information specific to line and reel number; a trace data block that follows the reel identification header, with the first 240 bytes of each trace block consisting of the binary trace identification header; and seismic data samples that follow the trace identification header.
Graphic image file: Printable versions of the processed subbottom profiles are available as GIF images and are included in the download file, 2015-331-FA_seisimag.zip.
Navigation file: Navigation files are available as ASCII text files. Provided are raw shotpoint navigation files, reprojected survey shotpoint navigation, 1,000-shot-interval locations, and start of line files. The final navigation files are provided in 2015-331-FA_nav.zip.
GIS file: The GIS data associated with this survey are provided as a compressed zip file, 2015-331-FA_arc.zip, which is composed of an Esri map document, shapefiles, a folder for the processed profile images, shapefile metadata and a readme file. The shapefiles provided may also be viewed using other versions of Esri desktop software including their free software Explorer for ArcGIS, which is available at http://www.esri.com/software/arcgis/explorer/index.html.
The entity and attribute information was generated by the individual and/or agency identified as the originator of the dataset. Please review the rest of the metadata record for additional details and information.
Arnell S. Forde
U.S. Geological Survey
Geologist
mailing and physical
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8000
aforde@usgs.gov
All of this publication is available online. The SEG Y files are also downloadable from the Coastal and Marine Geoscience Data System https://cmgds.marine.usgs.gov.
This publication was prepared by an agency of the United States Government. Although these data were processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
SEG Y
Revision 0
Winzip or 7zip
6730
https://coastal.er.usgs.gov/data-release/doi-F7668C5C/data/2015-331-FA_segy.zip
ASCII
Winzip or 7zip
4.40
https://coastal.er.usgs.gov/data-release/doi-F7668C5C/data/2015-331-FA_nav.zip
SHP (Esri shapefile)
Winzip or 7zip
1.70
https://coastal.er.usgs.gov/data-release/doi-F7668C5C/data/2015-331-FA_arc.zip
GIF
Winzip or 7zip
48.6
https://coastal.er.usgs.gov/data-release/doi-F7668C5C/data/2015-331-FA_seisimag.zip
None
Use of SEG Y data requires specialized seismic processing software, such as public domain software Seismic Unix http://www.cwp.mines.edu/cwpcodes/index.html.
20201013
Arnell S. Forde
U.S. Geological Survey
Geologist
mailing and physical
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8000
aforde@usgs.gov
Content Standard for Digital Geospatial Metadata
FGDC-STD-001-1998