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 ¯21

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:  ¯IPD16250.SGY
      sample rate:  4000.0 microsec
samples per trace:  ¯1301
      data length:  ¯5204 msec
  bytes per trace:  ¯5444
    bytes in file:  ¯131089676
   traces in file:  ¯24079
      first trace:  ¯260/1 FFID/trace
       last trace:  ¯229/31 FFID/trace


             file:  ¯IPD16454.SGY
      sample rate:  4000.0 microsec
samples per trace:  ¯1301
      data length:  ¯5204 msec
  bytes per trace:  ¯5444
    bytes in file:  ¯131160448
   traces in file:  ¯24092
      first trace:  ¯229/32 FFID/trace
       last trace:  ¯733/27 FFID/trace


             file:  ¯IPD16706.SGY
      sample rate:  4000.0 microsec
samples per trace:  ¯1301
      data length:  ¯5204 msec
  bytes per trace:  ¯5444
    bytes in file:  ¯132162144
   traces in file:  ¯24276
      first trace:  ¯733/28 FFID/trace
       last trace:  ¯240/15 FFID/trace

                              1
 
             file:  ¯IPD16959.SGY
      sample rate:  4000.0 microsec
samples per trace:  ¯1301
      data length:  ¯5204 msec
  bytes per trace:  ¯5444
    bytes in file:  ¯132178476
   traces in file:  ¯24279
      first trace:  ¯240/16 FFID/trace
       last trace:  ¯746/6 FFID/trace


             file:  ¯IPD17212.SGY
      sample rate:  4000.0 microsec
samples per trace:  ¯1301
      data length:  ¯5204 msec
  bytes per trace:  ¯5444
    bytes in file:  ¯132189364
   traces in file:  ¯24281
      first trace:  ¯746/7 FFID/trace
       last trace:  ¯252/47 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.

OB16250
OB16300
OB16340A
OB16340G
OB16350
OB16390
OB16440
OB16490
OB16540
OB16590
OB16640
OB16690
OB16740
OB16790
OB16840
OB16890
OB16940
OB16990
OB17040
OB17090
OB17140
OB17181
OB17181G
OB17231
OB17281
OB17331
OB17381
OB17431

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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