Formal Seismic Metadata

Identification_Information:

Citation:

Citation_Information:

Originator: Gina M. Brewer

Originator: Robert A. Morton

Originator: Dana S. Wiese

Publication_Date: 2001

Title: Archive of Boomer Seismic Reflection Data

Collected on USGS Cruise 99SCE01,

Little River Inlet to the entrance of Winyah Bay, South Carolina,

8 June - 16 June, 1999.

Geospatial_Data_Presentation_Form: Seismic Reflection Profile Section

Series_Information:

Series_Name: U.S. Geological Survey Open-File Report

Issue_Identification: 01-326

Publication_Information:

Publication_Place: St. Petersburg, FL

Publisher: U.S. Geological Survey

Description:

Abstract:

This report consists of two-dimensional marine seismic reflection profile

data from South Carolina. These data were acquired in June of 1999 with

the Research Vessel G.K. Gilbert. The data are available in a variety of formats,

including binary, ASCII, HTML, and GIF images. Binary data are in Society of

Exploration Geologists (SEG) SEG-Y format and may be downloaded for further

processing or display. Reference maps and GIF images of the profiles may be

viewed with your Web browser.

Purpose:

Marine seismic reflection data are used to image and map sedimentary and

structural features of the seafloor and subsurface. These data are useful

in mapping the extent and thickness of shallow sedimentary units in the

near shore region of South Carolina and in assessing other submarine geologic

characteristics and features. The main objective of this cruise was to

determine the characterization of the geological framework in the near shore

region, between Little River Inlet to the entrance of Winyah Bay, for ongoing

erosion studies.

Supplemental_Information:

Seismic reflection profiles are acquired by means of an acoustic source

(usually generated electronically), and a hydrophone or hydrophone array.

Both elements are typically towed in the water behind a survey vessel.

The sound source emits a short acoustic pulse, which propagates through

the water and sediment columns. The acoustic energy is reflected at

density boundaries (such as the seafloor or sediment layers beneath the

seafloor), and detected at the hydrophone. This process is repeated at

intervals ranging between 100 ms and 1s depending on the source type. In

this way a two-dimensional image of the geologic structure beneath the

ship track is constructed.

Seismic data are stored in SEG-Y format, which is a standard digital

format that can be read and manipulated by most seismic-processing

software packages. The SEG-Y file format includes a 3200-byte descriptive

header that contains detailed information regarding the data acquisition and

processing parameters. All data presented here are stored in SEG-Y, Integer,

Motorola format. The SEG-Y formatted trace data files have a .tra extension.

Additional recording parameters for each seismic data file can also be found

in the .par file associated with each .tra file. However, the .par files and the

trim_gga.pln file are only needed to replay the data with Triton Elics Delph

Seismic software. WARNING: The acquisition system used to collect the

seismic data presented in this report, may have added 6 ms to the top of

each seismic trace. However, since no bathymetric data was simultaneously

collected with the seismic data we have no way of proving that the added

6 ms does exist for this data set.

The seismic source employed here was a "boomer" transducer towed on

a sled at the sea surface providing 100 joules per shot. The reflected

energy was received by an Innovative Transducer Inc. (ITI) solid core

streamer and recorded by PC-based Triton-Elics Delph Seismic acquisition

software. The ITI streamer contains 10 hydrophones evenly spaced over 6

meters however only data received by elements 5-8 where summed, resulting

in a higher signal to noise ratio for the data. The streamer was positioned

parallel to the boomer sled and laterally separated from it by 7 m.

The sled was towed 20 m behind the GPS antennae. The sample frequency

of the data was 16000 Hz and the total record length was 100 ms. The

fire rate was every 0.25 sec, which resulted in a shot spacing of about

0.5 m based on survey speeds of 3.5-4 knots.

Differential GPS navigation was fed to the acquisition system every

second by the R/V G.K. Gilbert's onboard navigation system, a Trimble

Nav Graphic receiver. The accuracy of this receiver is within 100 m,

however, the data proved to be of poor quality and required extensive

editing. A filter was designed to remove spurious data values and these

edited results can be used to generate trackline maps at any scale or

projection desired, however the data has not been corrected to

reflect the 20 m offset between the source and the GPS antenna. Also

the raw navigation files did not have year or Julian day written to the headers.

This information was handwritten into the edited and shotpoint navigation files.

Position fixes for every 500th shotpoint are also provided as an aide for

easy registering of the data after projection. The trackline maps provided in

this report are geographic projections (no datum) and were created using

ESRI's GIS software ArcView 3.2 and exported to Adobe Illustrator for

further editing, then saved as GIF images. These GIF images are viewable

with your WWW browser. All navigation files are stored as flat ASCII text files.

Time_Period_of_Content:

Time_Period_Information:

Range_of_Dates/Times:

Beginning_Date: 19990608

Ending_Date: 19990616

Currentness_Reference:

Data assumed to be constant over time but may

change due to geologic processes.

Status:

Progress: Complete

Maintenance_and_Update_Frequency: None Planned

Spatial_Domain:

Bounding_Coordinates:

West_Bounding_Coordinate: -79.18 W

East_Bounding_Coordinate: -78.55 W

North_Bounding_Coordinate: 33.84 N

South_Bounding_Coordinate: 33.19 N

Keywords:

Theme:

Theme_Keyword_Thesaurus: none

Theme_Keyword: marine seismic reflection

Theme_Keyword: boomer

Theme_Keyword: 99SCE01

Theme_Keyword: ISO 9660 CD-ROM

Theme_Keyword: SEG-Y

Place:

Place_Keyword_Thesaurus: none

Place_Keyword: South Carolina/Georgia Coastal Erosion Study: Phase II

Place_Keyword: Charleston Harbor

Place_Keyword: Murrell's Inlet

Place_Keyword: Winyah Bay

Place_Keyword: Myrtle Beach

Place_Keyword: Little River Inlet

Access_Constraints: None. These data are held in the public domain.

Use_Constraints:

The U.S. Geological Survey request to be acknowledged

as the originator of the data in future products or

derivative research.

Point_of_Contact:

Contact_Information:

Contact_Person_Primary:

Contact_Person: Robert A. Morton

Contact_Organization: U.S. Geological Survey

Contact_Position: Geologist

Contact_Address:

Address_Type: mailing address

Address: 600 Fourth Street South

City: St. Petersburg

State_or_Province: FL

Postal_Code: 33701

Country: USA

Contact_Voice_Telephone: (727) 803-8747 X3080

Contact_Electronic_Mail_Address: rmorton@usgs.gov

Browse_Graphic:

Browse_Graphic_File_Name: CDROM/MAPS/SCMAP.GIF

Browse_Graphic_File_Description:

Map of trackline data collected on USGS cruise 99SCE01,

in June of 1999, in the near shore region of South Carolina

between Little River Inlet and the entrance to Winyah Bay.

This map is a geographic projection (no datum) with the NOAA

chart 11535 in the background as a geotif. It was created in

ESRI's GIS software ArcView 3.2, then exported to Adobe

Illustrator for further editing and saved as a GIF image.

Browse_Graphic_File_Type: GIF

Browse_Graphic:

Browse_Graphic_File_Name: CDROM/MAPS/groupa.gif

Browse_Graphic_File_Description:

This is a map of trackline data, containing only

group A tracklines. This map is a geographic

projection (no datum) with the NOAA chart 11535 in

the background as a geotif. It was created in ArcView

3.2, and then exported to Illustrator and saved as a GIF

image. This map also contains every 500th shotpoint position

information for tracklines in group A.

Browse_Graphic_File_Type: GIF

Browse_Graphic:

Browse_Graphic_File_Name: CDROM/MAPS/groupb.gif

Browse_Graphic_File_Description:

This is a map of trackline data, containing only

group B tracklines. This map is a geographic

projection (no datum) with the NOAA chart 11535 in

the background as a geotif. It was created in ArcView

3.2, and then exported to Illustrator and saved as a GIF

image. This map also contains every 500th shotpoint position

information for tracklines in group B.

Browse_Graphic_File_Type: GIF

Browse_Graphic:

Browse_Graphic_File_Name: CDROM/MAPS/groupc.gif

Browse_Graphic_File_Description:

This is a map of trackline data, containing only

group C tracklines. This map is a geographic

projection (no datum) with the NOAA chart 11535

in the background as a geotif. It was created in ArcView

3.2, and then exported to Illustrator and saved as a GIF

image. This map also contains every 500th shotpoint position

information for tracklines in group C.

Browse_Graphic_File_Type: GIF

Browse_Graphic:

Browse_Graphic_File_Name: CDROM/MAPS/groupd.gif

Browse_Graphic_File_Description:

This is a map of trackline data, containing only

group D tracklines. This map is a geographic

projection (no datum) with the NOAA chart 11535

in the background as a geotif. It was created in ArcView

3.2, and then exported to Illustrator and saved as a GIF

image. This map also contains every 500th shotpoint position

information for tracklines in group D.

Browse_Graphic_File_Type: GIF

Browse_Graphic:

Browse_Graphic_File_Name: CDROM/MAPS/groupe.gif

Browse_Graphic_File_Description:

This is a map of trackline data, containing only

group E tracklines. This map is a geographic

projection (no datum) with the NOAA chart 11535

in the background as a geotif. It was created in ArcView

3.2, and then exported to Illustrator and saved as a GIF

image. This map also contains every 500 shotpoint position

information for tracklines in group E.

Browse_Graphic_File_Type: GIF

Data_Set_Credit:

We thank Rich Young with the USGS and Dave Bennett with Eckerd

College, captains of the R/V G.K. Gilbert, for their help in the data

collection; BJ Reynolds with the USGS, in St.Petersburg, Fla. for

his contribution to the data collection process; Dave Foster and

Jenna Hill, of the USGS Seafloor Mapping Group in Woods Hole, Mass.

for providing examples of their archives; Jon Childs with the USGS, in

Menlo Park, Calif. who provided examples of his formal metadata;

Brock Murch and Bryan McCloskey at the USGS, in St.Petersburg,

Fla. for their programming efforts in editing the navigation files; Shawn

Dadisman at the USGS, in St.Petersburg, Fla. for her help with the

content and layout; Trent Faust and Rob Wertz with the USGS in St.

Petersburg for their help in the web design and technical layout of the

CD-ROM; and Laura Moore and Jack Kindinger also both with the USGS

in St.Petersburg, Fla. for their technical and editorial reviews.

Native_Data_Set_Environment: SEG-Y

Data_Quality_Information:

Attribute_Accuracy:

Attribute_Accuracy_Report:

The validity or accuracy of marine seismic reflection profiles

is highly qualitative, and depends on equipment and operating

condition variables. Visual inspection of the images rendered

from the data did not show any major anomalies.

WARNING: The acquisition system used to collect the seismic data

presented in this report, may have added 6 ms to the top of each

seismic trace. However, since no bathymetric data was simultaneously

collected with the seismic data we have no way of proving that the added

6 ms does exist for this data set.

Logical_Consistency_Report: This data set is from a single cruise with

consistent instrument calibrations.

Completeness_Report:

These data are collected along tracklines (2D).

Therefore, data are inherently incomplete. Geologic details between

lines must be inferred. All tracklines were recorded to 100ms. There

was no data collected for lines 7,8 or 9.

Positional_Accuracy:

Horizontal_Positional_Accuracy:

Horizontal_Positional_Accuracy_Report:

The position accuracy was determined with the onboard navigation

system, a Trimble Nav Graphic receiver in differential mode.

Absolute position accuracy was within 100 m.

Vertical_Positional_Accuracy:

Vertical_Positional_Accuracy_Report:

The vertical position was local sea level and there has been no

corrections to a datum or for tidal variations.

Lineage:

Process_Step:

Process_Description: Boomer processing:

Raw SEG-Y data was processed with SU and (Triton Elics Software)to

produce the GIF formatted seismic profiles included in this report.

A representative data processing sequence consisted of:

1)Bandpass filter: 300-500-2500-3000 Hz;

2)Automatic gain control;

3)Postscript display at 25ms/in and 300shots/in for all tracklines.

4)Convert Postscripts to GIF format

Process_Date: 2001

Process_Step:

Process_Description: Positional (navigation) data:

As the seismic reflection data were acquired, the position of the

vessel was continuously determined with the Differential Global

Positioning System (DGPS). Positions were recorded approximately

every second, and written to the SEG-Y header. The ASCII navigation

files were extracted from the SEG-Y headers using SU scripts.

Process_Date: 2001

Process_Step:

Process_Description: Editing navigation:

The ASCII navigation files were extracted from the SEG-Y

headers, and then run through a filter to edit out the

spurious fixes. The filtered data was also reformatted for

use with ESRI's GIS software ArcView 3.2. The edited

navigation files also had year and Julian day handwritten

to each file.

Process_Date: 2001

Process_Step:

Process_Description: Open File preparation:

No processing has been done to the SEG-Y data files provided

on this CD-ROM. The data were displayed as 8-bit gray scale

Postscript files using the Seismic Unix 'psimage' algorithm.

The Postscript images were then converted to GIF images with

Aladdin Ghostscript. Only the GIF images are presented here.

Process_Date: 2001

Spatial_Data_Organization_Information:

Indirect_Spatial_Reference:

Horizontal X and Y locations (latitude and longitude) for each shot

location are provided in ASCII position files, along with the time the

shot was recorded in Greenwich Mean Time (GMT).

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Geographic:

Latitude_Resolution: 0.000278

Longitude_Resolution: 0.000278

Geographic_Coordinate_Units: decimal degrees

Geodetic_Model:

Horizontal_Datum_Name: WGS 84

Ellipsoid_Name: WGS 1984

Semi-major_Axis: 6378137 m

Denominator_of_Flattening_Ratio: 298.257

Entity_and_Attribute_Information:

Overview_Description:

Entity_and_Attribute_Overview: Binary data file:

Each profile is available as a binary file in Society of Exploration

Geophysicists SEG-Y format. A SEG-Y file consists of 1) a 3200-byte

file identification record of ASCII formatted general information;

2) a 400-byte binary record with information such as sample rate and

record length specific to the data set; and 3) multiple records,

one seismic reflection trace per record. Each trace record is preceded

by a 240-byte "trace header" containing information such as trace

number and acquisition day and time specific to each trace. The trace

data are represented as a time series of unit less 16-bit integer or

32-bit real numbers proportional to the reflection coefficient.

The SEG-Y file is useful only if you have access to specialized

software designed to process and display seismic reflection data.

These SEG-Y files have a .tra extension. These .tra files range in

size from the smallest being 14 MB to the largest being 142 MB.

Entity_and_Attribute_Detail_Citation:

Barry, K.M., Cavers, D.A., and Kneale, C.W., 1975, Recommended

standards for digital tape formats: Geophysics, v. 40, n. 2,

p. 344 - 352. Also available online at:

<http://www.seg.org/publications/tech-stand/index_body.html>

Entity_and_Attribute_Overview:

Graphic image file:

Each profile is available as a GIF image. The trackline maps

provided are GIF images that contain hot-links to the seismic profile

GIF images. The profiles range in size from 560KB to 5.8MB.

Distribution_Information:

Distributor:

Contact_Information:

Contact_Person_Primary:

Contact_Person: Rob Wertz

Contact_Organization: U.S. Geological Survey

Contact_Position: Manager - Data Management Group

Contact_Address:

Address_Type: Mailing address

Address: 600 Fourth Street South

City: St. Petersburg

State_or_Province: FL

Postal_Code: 33701

Country: USA

Contact_Voice_Telephone: (727) 803-8747 X3045

Contact_Electronic_Mail_Address: rwertz@usgs.gov

Contact_Instructions:

Data may be available on-line only by special

arrangement with the distributor above.

Resource_Description: U.S. Geological Survey Open-File Report 01-XXX CD-ROM

Distribution_Liability:

This Compact Disc-Read Only Memory (CD-ROM) publication was prepared

by an agency of the United States Government. Neither the United States

Government nor any agency thereof, nor any of their employees, make any

warranty, expressed or implied, or assumes any legal liability or

responsibility for the accuracy, completeness, or usefulness of any

information, apparatus, product, or process disclosed in this report,

or represents that its use would not infringe privately owned rights.

Reference therein to any specific commercial product, process, or service

by trade name, trademark, manufacturer, or otherwise does not necessarily

constitute or imply its endorsement, recommendation, or favoring by the

United States Government or any agency thereof. Any views and opinions of

authors expressed herein do not necessarily state or reflect those of

the United States Government or any agency thereof.

Although all data published on this CD-ROM have been used by the USGS, no

warranty, expressed or implied, is made by the USGS as to the accuracy of

the data and related materials and/or the functioning of the software. The

act of distribution shall not constitute any such warranty, and no

responsibility is assumed by the USGS in the use of this data, software,

or related materials.

Standard_Order_Process:

Digital_Form:

Digital_Transfer_Information:

Format_Name: SEG-Y

Format_Information_Content:

The SEG-Y standard format (Barry and others, 1975) consists of

the following: a 3600-byte reel identification header with the

first 3200 bytes consisting of an ASCII header block and a

400-byte binary header block. Both headers include information

specific to line and reel number. The trace data block follows

the reel identification header. The first 240 bytes of each trace

block is the binary trace identification header. The seismic data

samples follow the trace identification header.

File_Decompression_Technique: none

Transfer_Size: 650 MB

Digital_Transfer_Option:

Offline_Option:

Offline_Media: CD-ROM

Recording_Format: ISO 9660

Compatibility_Information: Unix, Linux, DOS, MAC

Fees: available from the Denver Open-File Sales department, prices vary.

Technical_Prerequisites:

Use of SEG-Y data requires specialized seismic processing

software, such as Unix or Linux based public domain

software Seismic Unix (SU) developed by the Colorado School

of Mines, Center for Wave Phenomena, which can be downloaded

from <http://www.cwp.mines.edu/cwpcodes> free of charge.

Metadata_Reference_Information:

Metadata_Date: 20010410

Metadata_Contact:

Contact_Information:

Contact_Person_Primary:

Contact_Person: Gina M. Brewer

Contact_Organization: U.S. Geological Survey

Contact_Position: Geologist - Data Management Group

Contact_Address:

Address_Type: Mailing address

Address: 600 Fourth Street South

City: St. Petersburg

State_or_Province: FL

Postal_Code: 33701

Country: USA

Contact_Voice_Telephone: (727) 803-8747 X3120

Contact_Electronic_Mail_Address: gmbrewer@usgs.gov

Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata

Metadata_Standard_Version: FGDC-STD-001-1998

FORMAL SEISMIC METADATA