Originator: Arnell S. Forde
Originator: Jake J. Fredericks
Originator: James G. Flocks
Archive of Chirp Subbottom Profile Data Collected in 2017 from the Louisiana Chenier Plain
Geospatial_Data_Presentation_Form: multimedia presentation
Series_Name: U.S. Geological Survey Data Release
Publication_Place: St. Petersburg, Florida
U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center
June 2–10 and July 2, 2017, the U.S. Geological Survey (USGS) conducted geophysical surveys offshore of the Louisiana Chenier Plain to document the changing morphology of the coastal environment. Data were collected under the Barrier Island Coastal Monitoring (BICM) program, an ongoing collaboration between the State of Louisiana Coastal Protection and Restoration Authority (CPRA), the University of New Orleans (UNO) Pontchartrain Institute for Environmental Sciences (PIES), and the USGS. Project objectives include compiling historical shoreline bathymetric datasets and comparing them to other bathymetric data collected during the BICM project. At the same time, subsurface geophysical data were collected to investigate the geomorphology and geologic controls on barrier-shoreline evolution. This publication serves as an archive of unprocessed, digital chirp subbottom data, survey trackline maps, 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 (CMGDS, https://cmgds.marine.usgs.gov)
To archive all digital chirp subbottom profile data and associated files collected during Field Activity Numbers 2017-323-FA (project ID, 17BIM01) and 2017-324-FA (17BIM05). Additional survey and data details are available from CMGDS at, https://cmgds.marine.usgs.gov/
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. Transducers and receivers are contained within the towfish, which 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 both surveys consisted of an EdgeTech SB-424 towfish running Discover version 4.09 acquisition software and towed on the port side of the R/V Sallenger, approximately 3.5 m opposite the global positioning system (GPS) antenna. These data have not been corrected for layback. The data were acquired using a frequency sweep of 4–24 kilohertz (kHz), a 43 kHz sample frequency, and recording length was approximately 66.5 ms. Based on survey speeds of 3.5-4.5 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 (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, 2017_Chenier_logs.zip.
Currentness_Reference: ground condition
Maintenance_and_Update_Frequency: None planned
Access_Constraints: None. These data are held in the public domain.
Theme_Keyword_Thesaurus: USGS Metadata Identifier
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword_Thesaurus: USGS Thesaurus
Theme_Keyword: sub-bottom profiling
Theme_Keyword: marine geology
Theme_Keyword: coastal processes
Theme_Keyword_Thesaurus: Data Categories for Marine Planning
Theme_Keyword: physical habitats and geomorphology
Theme_Keyword_Thesaurus: Marine Realms Information Bank (MRIB) Keywords
Theme_Keyword: seismic reflection profiling
Theme_Keyword: Seismic reflection
Theme_Keyword: Society of Exploration Geophysicists
Theme_Keyword: SEG Y
Theme_Keyword: Barrier Island Mapping
Place_Keyword_Thesaurus: Common Geographic Areas
Place_Keyword: United States
Place_Keyword: Grand Chenier
Place_Keyword: Cheniere Au Tigre
Place_Keyword: Pecan Island
Place_Keyword: Sabine Pass
Place_Keyword: White Lake
Place_Keyword: Gulf of Mexico
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.
Contact_Person: Arnell S. Forde
Contact_Organization: U.S. Geological Survey
Address_Type: mailing and physical
Contact_Voice_Telephone: (727) 502-8000
Address: 600 4th Street South
City: Saint Petersburg
Funding and (or) support for this study was provided by the USGS Coastal and Marine Geology and Barrier Island Coastal Monitoring programs. The authors thank Andy Farmer of Cherokee Nation Technologies for his assistance in data collection and piloting the research vessel (R/V) Sallenger. This document was improved by scientific/editorial and metadata reviews from reviewer 1 and Chelsea Stalk 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 10.6.1 (Build 8321).
Originator: Barry, K.M., Cavers, D.A., and Kneale, C.W.
Title: Recommended standards for digital tape formats
Other_Citation_Details: pages 344-352
Issue_Identification: v. 40, no. 2
Originator: Cohen, J.K., and Stockwell, J.W., Jr., CWP/SU
Seismic Un*x Release No. 44: An open source software package for seismic research and processing
Publication_Place: Golden, Colorado
Publisher: Center for Wave Phenomena, Colorado School of Mines