U.S. Geological Survey
2009
JPEG images of seismic data collected offshore of the Chandeleur Islands, LA, 2007.
raster digital data
Woods Hole, MA
U.S. Geological Survey
USGS Open-File Report
2008-1195
http://pubs.usgs.gov/of/2008/1195/GIS_catalog/Seisimage/seisimage_07007.zip
Wayne E. Baldwin
Elizabeth A. Pendleton
David C. Twichell
2009
Geophysical Data from offshore of the Chandeleur Islands, Eastern Mississippi Delta
raster digital data
Open-File Report
2008-1195
Woods Hole, MA
U.S. Geological Survey
http://pubs.usgs.gov/of/2008/1195/
1.0
1.0
07007_metadata_holder.txt
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.
JPEG images of each seismic profile were generated in order to incorporate images of the seismic data into Geographic Information System (GIS) projects and data archives utilizing HTML. These JPEG images represent approximately 1655 km of chirp seismic data collected with the Edgetech 512i in 2007. This format is universal and yields an easily browseable pictorial view of the seismic profiles. Each profile image is hotlinked to its corresponding trackline navigation contained within a polyline shapefile (seismic_trk_07007.shp), and even 500 shot-point locations are available in a point shapefile (seismic_sht_07007.shp). All of these data are available in an ESRI ArcMap project, as well as separate .zip archives on this digital data DVD archive (http://pubs.usgs.gov/of/2008/1195/GIS_catalog/).
en
20070610
20070622
ground condition
None planned
-89.293553
-88.883122
29.661442
29.381022
General
U.S. Geological Survey
USGS
Woods Hole Science Center
WHSC
Coastal and Marine Geology Program
CMGP
JPG
JPEG
seismic-reflection
SEGY
profiles
seismic
subbottom
image
chirp
WHSC field activity serial number 06015
General
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
ISO 19115 Topic Category
geoscientificInformation
oceans
oceans and coastal
oceans and estuaries
imageryBaseMapsEarthCover
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
Microsoft Windows XP Professional x64 Edition Version 2003 Service Pack 2
http://pubs.usgs.gov/of/2008/1195/images/seis_imag.jpg
JPEG image of seismic-reflection profile
JPEG
JPEG
John Stockwell
CWP/SU: Seismic Uni*x
2008
document
Golden, CO
Center for Wave Phenomena - Colorado School of Mines
http://www.cwp.mines.edu/cwpcodes/index.html
Paul Henkart
SIOSEIS
2007
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
SEGY Rev.1 Data Exchange Format1
2002
document
Tulsa, OK
Society of Exploration Geophysicists
http://www.seg.org/SEGportalWEBproject/prod/SEG-Publications/Pub-Technical-Standards/Documents/seg_y_rev1.pdf
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.
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
jsftosegy (version: none)
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
SIOSEIS (version: 96.4)
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
Seisworks 2-D(version: R2003.12.0.0)
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
SIOSEIS (version: 96.4)
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
Seismic Unix (version: 4.1); ImageMagick (version: 5.5.6)
U.S. Geological Survey
disc
20070610
20070622
ground condition
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.
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
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.
WinZip
Joint Photographic Experts Group
WinZip files contains compressed images of processed seismic-reflection profiles as well as associated metadata.
Use WinZip or pkUnzip
500 MB
500 MB
9.0
http://pubs.usgs.gov/of/2008/1195/GIS_catalog/Seisimage/seisimage_07007.zip
Data can be downloaded via the World Wide Web (WWW)
DVD-ROM
4.75
Gbytes
UDF
none
Downloadable Data
These data can be viewed with any JPEG image viewing software.
Digital copies of these chirp seismic data may also be obtained in the SEG-Y Rev. 1 standard format upon request. The data would be packaged on DVD, and contain the chirp-processed, envelope traces subsequent to conversion from raw JSF format.
20080403
2008
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
None
None
en
local time
http://www.esri.com/metadata/esriprof80.htmlESRI Metadata Profile
20080328
15284900
FALSE
20090128
16014400
{0542A821-11AF-4A59-8752-DCC588E37493}
20090128
16011400
20090128
Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 3; ESRI ArcCatalog 9.2.6.1500
07007_metadata_holder.txt
ISO 19115 Geographic Information - Metadata
DIS_ESRI1.0
dataset
002
Text File