Citation:
Citation_Information:
Originator: Arnell S. Forde
Originator: Shawn V. Dadisman
Originator: James G. Flocks
Originator: Dana S. Wiese
Publication_Date: 2011
Title:
Archive of Digital Chirp Subbottom Profile Data Collected During USGS Cruises 09CCT03 and 09CCT04, Mississippi and Alabama Gulf Islands, June and July 2009
Geospatial_Data_Presentation_Form: Subbottom Profile Section
Series_Information:
Series_Name: U.S. Geological Survey Data Series
Issue_Identification: 590
Publication_Information:
Publication_Place: St. Petersburg, FL
Publisher: U.S. Geological Survey
Online_Linkage: http://cmgds.marine.usgs.gov/data/09cct03/chirp/
Online_Linkage: http://cmgds.marine.usgs.gov/data/09cct04/chirp/
Description:
Abstract:
In June and July of 2009, the U.S. Geological Survey conducted geophysical surveys to investigate the geologic controls on island framework from Cat Island, Mississippi, to Dauphin Island, Alabama, as part of a broader USGS study of Coastal Change and Transport (CCT). This report serves as an archive of unprocessed digital Chirp seismic reflection data, trackline maps, navigation files, Geographic Information System (GIS) files, Field Activity Collection System (FACS) logs, observer's logbook, and formal Federal Geographic Data Committee (FGDC) metadata. Gained (a relative increase in signal amplitude) digital images of the seismic profiles are also provided.
For more information on the seismic surveys see
http://walrus.wr.usgs.gov/infobank/c/c309gm/html/c-3-09-gm.meta.html and
http://walrus.wr.usgs.gov/infobank/g/g409gm/html/g-4-09-gm.meta.html
These data are also available via GeoMapApp (
http://www.geomapapp.org/) and Virtual Ocean (
http://www.virtualocean.org/) earth science exploration and visualization applications.
Purpose:
To archive all digital Chirp subbottom profile data and associated files collected during cruises 09CCT03 and 09CCT04. NOTE: Cruise 09CCT03A survey data were collected as a subset during cruise 09CCT03; this dataset is restricted to Cat Island. Although listed as a separate cruise (in this archive and on the FACS forms), it was not officially assigned a unique ID by the St. Petersburg Coastal and Marine Science Center (SPCMSC); this naming convention was adopted in the field to help distinguish this smaller cruise from the larger one during the data acquisition and archival processes.
Supplemental_Information:
The USGS SPCMS assigns a unique identifier to each cruise or field activity. For example, 09CCT03 and 09CCT04 tell us the data were collected in 2009 for research on Coastal Change and Transport (CCT) and the data were collected during the third and fourth field activities for that study in that calendar year. Refer to <
http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html> for a detailed description of the method used to assign the cruise or field activity ID. The naming convention used for each subbottom line is as follows: yye##a, where 'yy' are the last two digits of the year in which the data were collected, 'e' is a 1-letter abbreviation for the equipment type (for example, c for 424 Chirp and i for 512i Chirp), '##' is a 2-digit number representing a specific track, and 'a' is a letter representing the section of a line if recording was prematurely terminated or rerun for quality or acquisition problems. All Chirp systems use a signal of continuously varying frequency; the EdgeTech SB-512i and SB-424 Chirp systems used during these surveys produce high resolution, shallow penetration (less than 50-ms) profile images beneath the seafloor. The towfish is a sound source and receiver, which is typically towed 1 - 2 m below the sea surface. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), detected by a receiver, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.125 s) and recorded for specific intervals of time (for example, 50 ms). In this way, a two-dimensional vertical image of the shallow geologic structure beneath the ship track is produced. The seismic source employed during 09CCT03 consisted of an EdgeTech SB-424 towfish running EdgeTech's DISCOVER v. 3.50 acquisition software and towed about 2 m behind the GPS antenna. The frequency range for the entire cruise was 4 - 20 kHz. Sample frequency of the data was 43 kHz, and record length was 100 ms. The source utilized during 09CCT04 consisted of an EdgeTech SB-512i towfish also running DISCOVER v. 3.50 acquisition software; however, it was towed about 9 m behind the GPS antenna. The frequency range varied between 1 - 10 kHz and 0.7 - 12 kHz. Sample frequency of the data was 43 kHz, and record length was 75 ms. Based on survey speeds of 3.5 knots, the shot spacing for both cruises was about 0.386 m. Standard SEG-Y format allows for the collection of 3 channels of trace data for each recorded shot of Chirp data. Channel 2 is the "real," or in-phase component of the signal, channel 1 is the "imaginary," or quadrature component of the signal, and channel 0 is the "envelope," or product of channels 1 and 2. The acquisition software used for these cruises only saves the envelope data; consequenly, only channel 0 was used to produce the profiles presented here. The archived trace data are in standard SEG-Y, IBM float format (Barry and others, 1975); the first 3,200 bytes of the card image header are in ASCII, instead of EBCDIC format. Some data were collected in the EdgeTech's proprietary JSF format and later converted to SEG-Y; all remaining lines were collected in both formats. The SEG-Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2010). The SEG-Y formatted trace files have a .sgy extension. Also provided are example SU scripts that allow the user to strip off navigation fixes from the SEG-Y headers, along with a fix for every 1,000 shots, and produce a printable, gained GIF image of each profile. The processed SEG-Y data were exported to Chesapeake Technology, Inc. (CTI) SonarWeb version 3.16.0096 PRO software to produce a geospatially interactive version of the profile that allows the user to obtain a geographic location and depth from the profile for a cursor position; this information is displayed in the status bar of the browser. Please note that clicking on the profile image switches it to "Expanded View" (a compressed image of the entire line), and cursor tracking is not available in this mode. NOTE: The only supported Web browsers that properly display all features of the geospatial profiles are Internet Explorer 8 or greater for Windows and Firefox 3.6 or greater for all platforms. For both browsers, the status bar and JavaScript must be enabled. Firefox also requires "Change status bar text" to be checked under Advanced JavaScript Options. If using Internet Explorer 8, you must disable scripts/Active X controls. To do this, right click the information bar (found at the top of the page), left click "Allow Blocked Content...", and then select "Yes". Use of other browsers may result in spurious or no information given in the status window. Firefox may be downloaded at <
http://www.mozilla.com/en-US/firefox/>. Macintosh Instructions (Firefox Only): From the Menu Bar go to Firefox > Preferences > Content (tab) > Checkmark "Enable JavaScript"> Click Advanced... > Checkmark "Change Status Bar Text". Verify that the status bar is enabled by selecting View from the Menu Bar and looking for a checkmark next to "Status Bar"; if the check is missing, highlight and select the text to activate the bar.
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20090609
Ending_Date: 20090701
Currentness_Reference: Data collection interval
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -89.167925
East_Bounding_Coordinate: -88.316583
North_Bounding_Coordinate: 30.269472
South_Bounding_Coordinate: 30.186064
Keywords:
Theme:
Theme_Keyword_Thesaurus: USGS Metadata Identifier
Theme_Keyword: USGS:bd0f8911-6580-47c1-80f5-0f1e12c3eded
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: geoscientificinformation
Theme_Keyword: oceans
Theme:
Theme_Keyword_Thesaurus: General
Theme_Keyword: Geology
Theme_Keyword: Coastal Information
Theme_Keyword: Marine
Theme_Keyword: Subbottom profile
Theme_Keyword: Seismic Reflection
Theme_Keyword: Chirp
Theme_Keyword: Society of Exploration Geophysicists
Theme_Keyword: SEG-Y
Theme_Keyword: Coastal Change and Transport
Theme_Keyword: CCT
Theme_Keyword: 09CCT03
Theme_Keyword: 09CCT04
Theme:
Theme_Keyword_Thesaurus: Data Categories for Marine Planning
Theme_Keyword: distributions
Theme_Keyword: substrate
Theme:
Theme_Keyword_Thesaurus: Marine Realms Information Bank (MRIB) Keywords
Theme_Keyword: seismic reflection
Theme_Keyword: marine geophysics
Theme:
Theme_Keyword_Thesaurus: USGS Thesaurus
Theme_Keyword: seismic reflection methods
Theme_Keyword: sub-bottom profiling
Theme_Keyword: marine geophysics
Place:
Place_Keyword_Thesaurus: Names Information System (GNIS) Content Charcterization
Place_Keyword: Mississippi
Place_Keyword: Alabama
Place_Keyword: Cat Island
Place_Keyword: West Ship Island
Place_Keyword: East Ship Island
Place_Keyword: Horn Island
Place_Keyword: Petit Bois Island
Place_Keyword: Dauphin Island
Place_Keyword: Biloxi Bay
Place_Keyword: Dog Keys Pass
Place_Keyword: Mississippi Sound
Place_Keyword: Gulf of Mexico
Access_Constraints: None. These data are held in the public domain.
Use_Constraints:
The USGS requests that it be acknowledged as originator of the data in future products or derivative research.
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Arnell Forde
Contact_Organization: USGS
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: Saint Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: (727) 803-8747 extension 3111
Contact_Electronic_Mail_Address: aharrison@usgs.gov
Browse_Graphic:
Browse_Graphic_File_Name:
Browse_Graphic_File_Description:
Location map of all digital subbottom profile data collected during USGS field activities 09CCT03, 09CCT03A, and 09CCT04. This map was created at a scale of 1:726,775.
Browse_Graphic_File_Type: JPEG
Browse_Graphic:
Browse_Graphic_File_Name: http://pubs.usgs.gov/ds/590/maps/cruisenav/09cct03_04_area1.jpg
Browse_Graphic_File_Description:
Area 1 trackline map of digital subbottom profile data collected from Horn Island to Dauphin Island (refer to figure 2 for location) during USGS field activities 09CCT03 and 09CCT04. This map was created at a scale of 1:229,950.
Browse_Graphic_File_Type: JPEG
Browse_Graphic:
Browse_Graphic_File_Name:
Browse_Graphic_File_Description:
Area 1a detailed trackline map of digital subbottom profile data collected offshore of Horn Island (refer to figure 3 for location) during USGS field activities 09CCT03 and 09CCT04. This map was created at a scale of 1:50,000.
Browse_Graphic_File_Type: JPEG
Browse_Graphic:
Browse_Graphic_File_Name:
Browse_Graphic_File_Description:
Area 1b detailed trackline map of digital subbottom profile data collected offshore of Horn and Petit Bois Islands (refer to figure 3 for location) during USGS field activities 09CCT03 and 09CCT04. This map was created at a scale of 1:32,000.
Browse_Graphic_File_Type: JPEG
Browse_Graphic:
Browse_Graphic_File_Name:
Browse_Graphic_File_Description:
Area 1c detailed trackline map of digital subbottom profile data collected offshore of Petit Bois Island (refer to figure 3 for location) during USGS field activities 09CCT03 and 09CCT04. This map was created at a scale of 1:49,250.
Browse_Graphic_File_Type: JPEG
Browse_Graphic:
Browse_Graphic_File_Name:
Browse_Graphic_File_Description:
Area 1d detailed trackline map of digital subbottom profile data collected offshore of Dauphin Island (refer to figure 3 for location) during USGS field activities 09CCT03 and 09CCT04. This map was created at a scale of 1:44,470.
Browse_Graphic_File_Type: JPEG
Browse_Graphic:
Browse_Graphic_File_Name: http://pubs.usgs.gov/ds/590/maps/cruisenav/09cct03_area2.jpg
Browse_Graphic_File_Description:
Area 2 trackline map of digital subbottom profile data collected offshore of Cat Island (refer to figure 2 for location) during USGS field activity 09CCT03A. This map was created at a scale of 1:71,000.
Browse_Graphic_File_Type: JPEG
Browse_Graphic:
Browse_Graphic_File_Name: http://pubs.usgs.gov/ds/590/profiles/printable/
Browse_Graphic_File_Description:
Directory containing printable images of all subbottom profiles. The record lengths for cruises 09CCT03 and 09CCT04 are 100 ms and 75 ms, respectively. Since no geologically significant structures could be seen in the 09CCT03 profiles below 50 ms, the printable profiles do not display data beyond this point.
Browse_Graphic_File_Type: GIF
Browse_Graphic:
Browse_Graphic:
Browse_Graphic:
Browse_Graphic:
Data_Set_Credit:
Funding for this study was provided by the USGS CMGP. We thank R/V Survey Cat captains Nancy DeWitt and B.J. Reynolds and R/V G.K. Gilbert captain Rich Young of the USGS - St. Petersburg, FL for their assistance in data collection. We would also like to thank Elizabeth Pendleton of the USGS Coastal and Marine Science Center - Woods Hole, MA, for her help in data processing. This document was improved by the reviews of Mark Hansen (USGS - SPCMSC) and Jamie Bonisteel-Cormier (Jacobs Technology Inc. - St. Petersburg, FL).