National Centers for Environmental Information (NCEI)

MULTICHANNEL COMMON DEPTH POINT (CDP)
SEISMIC REFLECTION DATA

Data Announcement 1976-R

* Third Data Set: Seismic data for Three Additional Atlantic Survey lines.

As part of a program by the U.S. Geological Survey (USGS) to gain a better understanding of the general geologic framework of the Continental Shelf, Slope, and Rise and its relationship to onshore geology and to help assess the petroleum potential of the Continental Margin, a number of multichannel common depth point (CDP) seismic reflection lines will be collected from the Atlantic, Pacific, and Alaskan coastal areas over the next several years. The National Centers for Environmental Information (NCEI) (formerly the National Geophysical Data Center (now the National Centers for Environmental Information)) of NOAA will serve as the agency to make these data available for general use as they are released by the USGS. This is to announce the availability of digital tapes and seismic sections for several survey lines on the Northeastern Atlantic Coast.
----------------
* The information on previous data sets is summarized within this flier. Additional data sets will be announced as they become available.

DESCRIPTION OF DATA

The CDP lines were recorded for USGS by Digicon, Inc. Acquisition of lines 1 through 3 was in August 1973 and lines 4 through 6 was in September-November 1974. Processing of the data was by Digicon, Inc. (for lines 1 through 3) and Geophysical Service, Inc. (for lines 4 through 6).

For Atlantic survey lines 1 through 6, distribution is in the form of (a) demultiplexed digital tapes, and (b) sepia or blackline copies of the processed sections, velocity profiles, and location maps.

DIGITAL TAPES - The field tapes have been demultiplexed and are available in SEG-Y format, 6250 BPI, on 9-track magnetic tape.

SEISMIC SECTIONS - While only full-scale (2.5 in./sec and 0.76 mi/in.) "AGC" scaled sections were available for lines 1 through 3, the data for lines 4 through 6 are available in either full- scale or half-scale (1.25 in./sec and 1.5 mi/in.) and include both "AGC" scaled sections and "true amplitude" sections. the sections for lines 4 through 6 were only processed for the shallower water depths of each line and include 36-fold summation (lines 1 through 3 contained either 6-, 12-, or 24-fold summation).

DOCUMENTATION - Velocity profiles, location maps, and shot point listings are included with orders for the seismic sections. The following table summarizes the quantity of data (numbers of sheets):

Survey    Scaled      True Amplitude      Velocity       Location
 Line    Sections         Section         Profiles          Maps

  1          5             none              112             3
  2          5             none               80             2
  3          6             none              108             2
  4          6               6                85             2
  5          4               4               117             1
  6          5               5               102             3

Demultiplexed digital tapes for multichannel CDP seismic data are available in SEG-Y format, 6250 bpi, on 9-track magnetic tape. The data are available for each line separately as follows:

        Line 1 (81 tapes and documentation
        Line 2 (52 tapes and documentation
        Line 3 (83 tapes and documentation
        Line 4 (135 tapes and documentation
        Line 5 (160 tapes and documentation
        Line 6 (234 tapes and documentation

Individual tapes (less than 1 line order) are available.

Seismic sections and associated documentation (e.g., velocity profiles and location maps) are available in sepia or blackline form as follows:

              Lines 1-3 (full-scale)
              Lines 4-6 (full-scale)
              Lines 4-6 (half-scale)

Shot-point navigation is available on magnetic tape or CD-ROM.