![]() |
|
Home | Read Me | Cruise Activity | Navigation Data | Seismic Data | USGS Software | Seismic Unix | Disclaimer
Identification_Information:
Citation:
Citation_Information:
Originator: Gina M. Brewer
Originator: Shawn V.
Dadisman
Originator: James G.
Flocks
Originator: Dana S. Wiese
Originator: Jeffrey B. Davis
Publication_Date: 2001
Title:
Archive of Boomer
Seismic Reflection Data
Collected on USGS Cruise
99LCA01,
Crescent Beach Spring,
Florida,
26 April - 27 April,
1999.
Geospatial_Data_Presentation_Form: Seismic Reflection Profile Section
Series_Information:
Series_Name: U.S.
Geological Survey Open-File Report
Issue_Identification: 01-355
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 Crescent Beach Spring, Florida.
These data were acquired
in April 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 Geophysicists
(SEG) SEG-Y format and may be downloaded
for further processing or display. Trackline maps and GIF images
of the profiles may be
viewed with your WWW 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, the subsurface structure of the spring,
the depths to various
stratigraphic horizons, and in assessing other
submarine geologic characteristics and features near Crescent Beach Spring.
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 1 s
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 the data presented
in this report are stored in SEG-Y, integer, Motorola format. The SEG-Y
formatted trace data files
are located in the SEGY folder at the top
level of this disc and
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:
In order to comply with ISO 9660 naming standards
tracklines d118_1806,
d118_1812, and d118_1840 have been changed
to d1806, d1812,
and d1840 respectively on the trackline maps,
navigation files, and the SEG-Y data files.
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, except
for lines d118_12 and d118_1840 which were recorded to 200 ms. The
fire rate was every 0.5
sec, which resulted in a shot spacing
of about 1 m based on
survey speeds of 3.5-4 knots.
GPS navigation was
provided by a Trimble Centurian P-Code receiver
directly fed to the
acquisition system every second. The accuracy
of this receiver is within
15 m. However, the SEG-Y format only allows
for seconds of arc which is equivalent to 31 m. The shotpoint navigation
provided in this report
has not been corrected to reflect the 20 m
offset of the source to the GPS antenna. All navigation data are
stored in flat ASCII files
containing latitude and longitude values that can
be used to plot trackline
maps of the seismic profiles at any scale or map
projection desired. The
trackline maps provided on this disc are geographic
projections (no datum),
and were created with ESRI's GIS software
ArcView 3.2, exported to
Adobe Illustrator and then saved as a GIF images.
The images are viewable
with your WWW browser.
Also provided on this
CD-ROM are Seismic Unix (SU) scripts that allow
the user to strip off
navigation fixes from the SEG-Y headers along with
a fix for every 500th
shot. The seismic data is then converted to SU
format, filtered, gained
and both Postscript and GIF formatted images
are produced. These images
can them be displayed using a variety of
shareware programs such as
ghostview (Unix, Linux, MAC, Windows),
kview (Linux), or a web browser.
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 19990426
Ending_Date: 19990427
Currentness_Reference:
Data assumed to be consistent
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:
-80.21 W
East_Bounding_Coordinate:
-80.20 W
North_Bounding_Coordinate:
+29.77 N
South_Bounding_Coordinate:
+29.75 N
Keywords:
Theme:
Theme_Keyword_Thesaurus:
none
Theme_Keyword: marine
seismic reflection
Theme_Keyword: boomer
Theme_Keyword: 99LCA01
Theme_Keyword: ISO 9660
CD-ROM
Theme_Keyword: SEG-Y
Place:
Place_Keyword_Thesaurus:
none
Place_Keyword: Crescent Beach Spring
Place_Keyword: Florida
Place_Keyword: Anastasia
Island
Place_Keyword: Crescent
Beach
Access_Constraints: None.
These data are held in the public domain.
Use_Constraints:
The U.S. Geological Survey
ask 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: James G.
Flocks
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 X3012
Contact_Electronic_Mail_Address: jflocks@usgs.gov
Browse_Graphic:
Browse_Graphic_File_Name:
CDROM/MAPS/alllines.GIF
Browse_Graphic_File_Description:
Map of trackline data
collected on USGS cruise 99LCA01
in April of 1999, in
Crescent Beach Spring, off the coast
of Florida. This map is a
geographic projection (no datum),
which was created in
ESRI's GIS software ArcView 3.2.
It was 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/ln1_9.GIF
Browse_Graphic_File_Description:
A geographic projection of
a trackline map, created in
ArcView, and displaying
data for tracklines cres1-9,
collected during USGS
cruise 99LCA01 at Crescent
Beach Spring, Fla. This
map also contains every 500th
shotpoint position
information.
Browse_Graphic_File_Type: gif
Browse_Graphic:
Browse_Graphic_File_Name:
CDROM/MAPS/ln10_14.GIF
Browse_Graphic_File_Description:
A geographic projection of
a trackline map, created in
ArcView, and displaying
data for tracklines cres10-14,
collected during USGS
cruise 99LCA01 at Crescent
Beach Spring, Fla. This
map also contains every 500th
shotpoint position
information.
Browse_Graphic_File_Type:
gif
Browse_Graphic:
Browse_Graphic_File_Name:
CDROM/MAPS/15_1806.GIF
Browse_Graphic_File_Description:
A geographic projection of
a trackline map, created in
ArcView, and displaying
data for tracklines cres15, cres16,
cres16b, and d1806,
collected during USGS cruise 99LCA01 at
Crescent Beach Spring,
Fla. This map also contains every 500th
shotpoint position
information.
Browse_Graphic_File_Type:
gif
Browse_Graphic:
Browse_Graphic_File_Name:
CDROM/MAPS/1812_40.GIF
Browse_Graphic_File_Description:
A geographic projection of
a trackline map, created in
ArcView, and displaying
data for tracklines d1812 and
d1840, collected during
USGS cruise 99LCA01 at
Crescent Beach Spring,
Fla. This map also contains every
500th shotpoint position
information.
Data_Set_Credit:
This work was partially funded by the St. John's River Water
Management District located in Palatka, Fla. We thank
Rich Young, captain of the
R/V G.K. Gilbert for his help in the
data collection; 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; Trent
Faust and Rob Wertz with the
USGS in St. Petersburg, Fla. for
their help in the web design
and technical layout of the CD-ROM;
and Jack Kindinger and Peter Swarzenski also 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,
with the exception of an
added 6 ms to the top of each record that was
detected on future data
sets.
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.
Tracklines cres1-16, and d1806 were recorded to
100 ms, and lines d1812 and
d1840 were recorded to 200 ms.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
The position accuracy
was determined with Trimble Centurian
P-Code Receiver. This receiver's accuracy is within 15 m.
However, the SEG-Y
format only allows for seconds of arc
which is equivalent to 31
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. However, future data collected with this same system
have shown that up to 6
ms has been added to the top of each record.
Lineage:
Process_Step:
Process_Description:
Boomer processing
Raw SEG-Y data was
processed with Seismic Unix (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 50 ms/in and 300 shots/in
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 Global Positioning
System (GPS). GPS
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
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
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:
Longitude_Resolution:
Geographic_Coordinate_Units:
decimal degrees
Geodetic_Model:
Horizontal_Datum_Name: WGS
84
Ellipsoid_Name: WGS 84
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 2.3 MB to 60 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 84KB to 1.3MB.
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 does not
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 a EBCDIC
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: 650MB
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.
Ordering_Instructions: Most
open-file reports are available from USGS Information Services,
Box 25286, Federal
Center, Denver, CO 80225
(telephone: 303-202-4210;
e-mail: infoservices@usgs.gov).
Technical_Prerequisites:
Use of SEG-Y data requires
specialized seismic processing software,
such as Unix or Linux based
public domain software Seismic Unix
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: 20010328
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
Home | Read Me | Cruise Activity | Navigation Data | Seismic Data | USGS Software | Seismic Unix | Disclaimer