U.S. Geological Survey
2009
SEG-Y format of chirp seismic data collected offshore of the Chandeleur Islands, LA, 2007
1.0
raster digital data
Woods Hole Coastal and Marine Science Center, Woods Hole, MA
U.S. Geological Survey, Coastal and Marine Geology Program
https://cmgds.marine.usgs.gov/data/2007_007_FA/
In 2006 and 2007, the U.S. Geological Survey, in partnership with Louisiana Department of Natural Resources and the University of New Orleans, conducted geologic mapping to characterize the sea floor and shallow subsurface stratigraphy offshore of the Chandeleur Islands in Eastern Louisiana. The mapping was carried out during two cruises on the R/V Acadiana. Data were acquired with the following equipment: an SEA Ltd SwathPlus interferometric sonar (234 kHz), Klein 3000 dual frequency sidescan sonar, and an Edgetech 512i chirp subbottom profiling system. The long-term goal of this mapping effort is to produce high-quality geologic maps and geophysical interpretations that can be utilized to investigate the impact of Hurricane Katrina in 2005 and to identify sand resources within the region.
These chirp seismic-reflection data were collected to use for interpretation of shallow subsurface stratigraphy offshore the Chandeleur Islands, Louisiana.
For more information on the seismic surveys see https://cmgds.marine.usgs.gov/fan_info.php?fan=2007-007-FA. These data are also available via GeoMapApp (http://www.geomapapp.org/) and Virtual Ocean (http://www.virtualocean.org/) earth science exploration and visualization applications.
The JPEG format of these data (along with other data associated with this field activity) were released through the Open-File Report 2008-1195 (https://pubs.usgs.gov/of/2008/1195/). See the cross-reference for full citation information.
20070610
20070622
ground condition
None planned
-89.293553
-88.883122
29.661442
29.381022
USGS Metadata Identifier
USGS:f2ecb0be-3dd5-4e3b-86c1-be8ff617c1d6
None
U.S. Geological Survey
USGS
Woods Hole Science Center
WHSC
Coastal and Marine Geology Program
CMGP
seismic-reflection
SEGY
profiles
seismic
subbottom
image
chirp
WHSC field activity serial number 06015
ISO 19115 Topic Category
geoscientificInformation
oceans
imageryBaseMapsEarthCover
Data Categories for Marine Planning
distributions
substrate
Marine Realms Information Bank (MRIB) Keywords
seismic reflection profiling
marine geophysics
USGS Thesaurus
seismic reflection methods
sub-bottom profiling
marine geophysics
None
Louisiana
Chandeleur Islands
Breton Island
Gosier Island
Curlew Island
Mississippi River Gulf Outlet
New Harbor Islands
North Islands
North-Central Gulf Coast
United States
Gulf of Mexico
MRGO
none
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.
David C. Twichell
U.S. Geological Survey
Oceanographer
mailing and physical address
384 Woods Hole Rd.
Woods Hole
MA
02543-1598
(508) 548-8700x2266
(508) 457-2310
dtwichell@usgs.gov
https://pubs.usgs.gov/of/2008/1195/images/seis_imag.jpg
JPEG image of seismic-reflection profile
JPEG
Microsoft Windows XP Professional x64 Edition Version 2003 Service Pack 2
John Stockwell
2008
CWP/SU: Seismic Uni*x
document
Golden, CO
Center for Wave Phenomena - Colorado School of Mines
http://www.cwp.mines.edu/cwpcodes/index.html
Paul Henkart
2007
SIOSEIS
document
LaJolla, CA
Scripps Institution of Oceanography, University of California - San Diego
http://sioseis.ucsd.edu/index.html
Michael W. Norris and Alan K. Faichney
2002
SEGY Rev.1 Data Exchange Format1
document
Tulsa, OK
Society of Exploration Geophysicists
http://www.seg.org/documents/10161/77915/seg_y_rev1.pdf
Wayne E. Baldwin
Elizabeth A. Pendleton
David C. Twichell
2009
Geophysical Data from offshore of the Chandeleur Islands, Eastern Mississippi Delta
1.0
raster digital data
Open-File Report
2008-1195
Reston, VA
U.S. Geological Survey
https://pubs.usgs.gov/of/2008/1195/
Processed seismic data were converted to JPEG format for ease of seismic trace display. Quality control was conducted during processing.
Data Quality Problems:
Poor sea-state conditions periodically created problems with acquisition of the chirp seismic data during the ACAD07007 cruise. In most instances, heave removal processing (described in processing steps 2-4) greatly minimized the effects of sea state in the final trace data. However, the effects of particularly larger swells do remain within some of the final profiles. In the interest of preserving as much potentially interesting seafloor information as possible, we decided not to lengthen seafloor smoothing filters to the widths that would have been required to remove larger swells. We suggest viewing the JPEG image of line l44f1_000_h.jpg as a reference for the type of seismic artifacts that have been introduced as a result of excessive heave. In general, the artifacts will typically consist of a predictably undulating seafloor reflection that will often be accompanied by a reduction in along-track balance of the seismic traces (ie. vertical striping that alternates between lighter and darker groups of traces, producing a "fencepost"-like appearance). In light of these problems, we caution the interpretation of seafloor features that appear to be at the same scale of heave artifacts within profiles that are obviously affected by problematic sea states.
All acquired seismic data were processed and JPEG images produced.
The SB-0512i was towed approximately 6 m astern and approximately 1.5 m below the sea surface. DGPS navigation (assumed to be accurate within 1-2 m) was obtained from the receiver mounted above the interferometric sonar head, but towfish layback was not accounted for. The layback of the towfish adds additional uncertainty due to changes in angle and scope of the tow cable in response to sea state and vessel speed. The use of J-Star acquisition software during the ACAD07007 cruise caused a reduction in the resolution of navigation values recorded to the trace headers from the onboard DGPS. During acquisition, J-Star truncates the three least significant digits from the raw navigation string, which reduces the resolution of each navigation fix on the order of 1-2 meters. This error is evident in the ship-track polylines in the shapefile "seismic_trk_07007.shp", which display a "sawtooth" pattern when viewed at scales finer than approximately 1:3000. Based on horizontal offsets between the fish and GPS receiver, fish motion behind the vessel, and error associated with the acquisition system, the resulting positional accuracy is assumed to be +/- 20 m.
U.S. Geological Survey
unknown
Information unavailable from original metadata.
disc
20070610
20070622
ground condition
Information unavailable from original metadata.
Approximately 1655 km of high-resolution chirp seismic-reflection profiles were collected using an EdgeTech Geo-Star FSSB system and an SB-0512i towfish (0.5-12 kHz) on the R/V Acadiana of Loreauville, LA. EdgeTech J-Star acquisition software was used to control the Geo-Star topside unit and digitally log trace data in the JSF format. Data were acquired using a 0.25-s fire rate, a 5-ms pulse length, and a 0.5 to 8 kHz sweep (swept frequency). Tracklines are spaced 100 to 125 m apart in the shore parallel direction and about 1 km apart in the shore perpendicular direction.
jsftosegy (no version), a C script developed by Tom O'Brien (USGS - Woods Hole Seafloor Mapping Group) was used to convert raw chirp traces in the JSF format to chirp-processed, envelope traces in the SEG-Y rev. 1 standard format.
2007
Wayne E. Baldwin
U.S. Geological Survey
Geologist
mailing and physical address
384 Woods Hole Rd.
Woods Hole
MA
02543-1598
(508) 548-8700x2226
(508) 457-2310
wbaldwin@usgs.gov
A script was run that used SIOSEIS (version 96.4) to shift all traces by -2 ms vertically to account for the position of the 512i towfish beneath the sea surface. A second SIOSEIS script was used to predict the vertical location of the sea floor by identifying peak amplitudes within a vertical window. Two-way travel times (milliseconds) to the sea floor at each trace were recorded to an ASCII text file.
2006
Wayne E. Baldwin
U.S. Geological Survey
Geologist
mailing and physical address
384 Woods Hole Rd.
Woods Hole
MA
02543-1598
(508) 548-8700x2226
(508) 457-2310
wbaldwin@usgs.gov
All SEG-Y trace data were imported into Seisworks 2-D(version: R2003.12.0.0; Landmark Graphics Corp.), a 2-dimensional, digital seismic interpretation software, and seafloor values were imported as Seisworks horizon data. Spurious seafloor values were edited for discrete traces through heads-up digitization of the Seisworks horizon, and corrected values were exported to a new ASCII text file.
2006
Wayne E. Baldwin
U.S. Geological Survey
Geologist
mailing and physical address
384 Woods Hole Rd.
Woods Hole
MA
02543-1598
(508) 548-8700x2226
(508) 457-2310
wbaldwin@usgs.gov
An additional script was run that used SIOSEIS to remove sea surface heave and mute water column portions of the traces by: 1) loading the corrected seafloor times into the SEG-Y trace headers; 2) smoothing the sea floor picks using an along-track filter that approximates twice the period of sea surface heave to be removed (the filter window was set to use 46 traces); 3) creating a series of difference values between the raw and smoothed seafloor picks for each trace; 4) shifting traces up or down according to the difference values; and 5) muting each trace between time zero and the time of the smoothed sea floor pick, thus removing noise within the water column. Changes to the traces within each profile were saved to new "heave corrected" SEG-Y files, which were used for creation of JPEG browse images and digital interpretation.
2006
Wayne E. Baldwin
U.S. Geological Survey
Geologist
mailing and physical address
384 Woods Hole Rd.
Woods Hole
MA
02543-1598
(508) 548-8700x2226
(508) 457-2310
wbaldwin@usgs.gov
A script was run that used Seismic Unix (version 4.1) to read the SEG-Y files and plot the data as 8-bit gray scale Postscript files using the Seismic Unix 'psimage' algorithm. All images were created with a horizontal scale of 200 traces per inch. Images were plotted within a constant 8-inch vertical window of 50 milliseconds (Two-Way Travel Time) duration, yielding a vertical resolution of about 8.3 milliseconds per inch. The Postscript images were then converted to JPEG format using ImageMagick (version 5.5.6).
2006
Wayne E. Baldwin
U.S. Geological Survey
Geologist
mailing and physical address
384 Woods Hole Rd.
Woods Hole
MA
02543-1598
(508) 548-8700x2226
(508) 457-2310
wbaldwin@usgs.gov
Edits to the metadata were made to fix any errors that MP v 2.9.36 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). Attempted to modify http to https where appropriate. Fixed an online link in a cross-reference. The distribution format name was modified in an attempt to be more consistent with other metadata files of the same data format. The source information was incomplete and had to be modified to meet the standard. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent.
20170228
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
This metadata record was modified from one describing JPEG images to reflect the SEG-Y version of the same data (Open-File Report 2008-1195, https://pubs.usgs.gov/of/2008/1195/). Changes were made to the Citation and Distribution_Information.
20171120
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
Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog.
20171130
U.S. Geological Survey
Alan O. Allwardt
Contractor -- Information Specialist
Mailing and Physical
2885 Mission Street
Santa Cruz
CA
95060
831-460-7551
831-427-4748
aallwardt@usgs.gov
Added keywords section with USGS persistent identifier as theme keyword.
20200908
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
Raster
pixel
Wayne E. Baldwin
U.S. Geological Survey
Geologist
mailing and physical address
384 Woods Hole Rd.
Woods Hole
MA
02543-1598
(508) 548-8700x2226
(508) 457-2310
wbaldwin@usgs.gov
Downloadable Data
Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. 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.
SEG-Y
Link is to a folder containing SEG-Y files.
https://cmgds.marine.usgs.gov/data/2007_007_FA/
The online link gives access to the folder containing the individual SEG-Y files.
none
These data require software that can read SEG-Y data.
20200908
Wayne E. Baldwin
U.S. Geological Survey
Geologist
mailing and physical address
384 Woods Hole Rd.
Woods Hole
MA
02543-1598
(508) 548-8700x2226
(508) 457-2310
wbaldwin@usgs.gov
FGDC Content Standards for Digital Geospatial Metadata
FGDC-STD-001-1998
local time
None
None