U.S. DEPARTMENT OF THE INTERIOR / U.S. GEOLOGICAL SURVEY
                                
                                
        U.S. GEOLOGICAL SURVEY DIGITAL DATA SERIES DDS-13
                                
              International Phase of Ocean Drilling
                Seismic Line 1 Demultiplexed Data
               Cape Hatteras to Mid-Atlantic Ridge
                                
                            DISC ¯12

Demultiplexed Seismic Data

     Each file of seismic data is the disc-image of a SEG-Y
format tape output during the demultiplexing of the original
field data.  The data were written to tape using the 32 bit IBM
floating point format (Barry, and others, 1975).  As the data
were copied bit-for-bit to the CD-ROM file, this format was
preserved.  Each file of sesimic data is named IPD{number}, where
{number} is the first shotpoint in the file.  NOTE: FFID
indicates the Field File Identification Number assigned each shot
as it was recorded.

             file:  ¯IPD6748.SGY
      sample rate:  4000.0 microsec
samples per trace:  ¯1301
      data length:  ¯5204 msec
  bytes per trace:  ¯5444
    bytes in file:  ¯132608552
   traces in file:  ¯24358
      first trace:  ¯678/1 FFID/trace
       last trace:  ¯18/54 FFID/trace


             file:  ¯IPD6918.SGY
      sample rate:  4000.0 microsec
samples per trace:  ¯1301
      data length:  ¯5204 msec
  bytes per trace:  ¯5444
    bytes in file:  ¯129031844
   traces in file:  ¯23701
      first trace:  ¯18/55 FFID/trace
       last trace:  ¯9/9 FFID/trace


             file:  ¯IPD7100.SGY
      sample rate:  4000.0 microsec
samples per trace:  ¯1301
      data length:  ¯5204 msec
  bytes per trace:  ¯5444
    bytes in file:  ¯131427204
   traces in file:  ¯24141
      first trace:  ¯401/10 FFID/trace
       last trace:  ¯790/32 FFID/trace

                             1

             file:  ¯IPD7294.SGY
      sample rate:  4000.0 microsec
samples per trace:  ¯1301
      data length:  ¯5204 msec
  bytes per trace:  ¯5444
    bytes in file:  ¯127708952
   traces in file:  ¯23458
      first trace:  ¯790/33 FFID/trace
       last trace:  ¯168/54 FFID/trace

             file:  ¯IPD7483.SGY
      sample rate:  4000.0 microsec
samples per trace:  ¯1301
      data length:  ¯5204 msec
  bytes per trace:  ¯5444
    bytes in file:  ¯130365624
   traces in file:  ¯23946
      first trace:  ¯168/55 FFID/trace
       last trace:  ¯555/6 FFID/trace

             file:  ¯IPD7677.SGY
      sample rate:  4000.0 microsec
samples per trace:  ¯1301
      data length:  ¯5204 msec
  bytes per trace:  ¯5444
    bytes in file:  ¯3346216
   traces in file:  ¯614
      first trace:  ¯555/7 FFID/trace
       last trace:  ¯564/62 FFID/trace
























                             2


Observer Logs

     The following files are digitized versions of the original
observer's log sheets.  Each file is named OB{number}.{format},
where {number} is the first shot point on the page, and {format}
is the graphic format of the file: PCX, TIF, or GIF.  No {format}
extension is shown with the file names given below.

OB6710
OB6760
OB6810
OB6860
OB6900A
OB6910
OB6950
OB7000
OB7050
OB7100
OB7150
OB7200
OB7250
OB7300
OB7350
OB7400
OB7450
OB7500
OB7550
OB7600
OB7650



REFERENCE

Barry, K.M., Cavers, D.A., and Kneale, C.W., 1975, Recommended
     standards for digital tape formats: Geophysics, v. 40, p.
     344-352.









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