University of Bergen Institute of Solid Earth Physics Allé gt. 41, N-5007 Bergen, NORWAY Tel: (+47) 5558 3420 Fax: (+47) 5558 9669 http://www2.ifjf.uib.no/             Document information File name:  Last modified:  Initials: OM Rev.: 0.1 - draft Data / tape handling GFJ-294 Marine Seismic Field Course - September 2001

Recording parameters

• Data acquisition system: Geco Triacq, Nessie-3 streamer
• Number of channels: 240
• Number of auxilary channels: 0
• Number of samples per trace: 6144
• Sampling interval: 2 ms
• NPD Survey designation: "UIB-SV-01"

From field tape in SEG-D to SEG-Y on Exabyte tape

Conversion of raw data in DEG-D from 3480 tape to SEG-Y on Exabyte followed two different procedures. The first procedure was abandoned when release 35 of Seismic Unix permitted reading of SEG-D from files.

1. Procedure 1 (applies to data from line no. 2, 5 and 6)
   1. Data copied from the original raw tapes (3480 type) to DLT tape using the Triacq "TapeUtil" program; the DLT drive working under the Triacq SUN machine.
   2. The individual shotfiles extracted from these DLT tapes and written to disk files using a script "les-dlt.sh". The DLT reading took place on a Linux PC box with our second DLT tapedrive.
   3. The individual shot files written to Exabyte tape using a script described here.
   4. Exabyte shot files (still in SEG-D) read into Promax, demultiplexed and written to tape in SEG-Y format.
      
      
2. Procedure 2 (applies to all other lines)
   1. Data copied from the original raw tapes (3480 type) to disk files on the Triacq SUN machine, in so-called Tape Image Format (TIF). Each tape yields one TIF file.
   2. TIF files transferred to "pandora" (a SUN machine at IFJ) and Linux PC box and put into directories with profile names.
   3. Used a program called "tifread" to extract individual shotfiles from TIF files. Programmer credits: Kristian Hiim.
      • Header file tif.h
      • tifread.cc
   4. Script to demux SEG-D and write SEG-Y to tape. Two computers were used in parallell, the PC Linux box and "pandora".
      • PC Linux box tape writing script (called write_tape)
      • Pandora tape writing scripts (called e.g. write_tape-P21-A for the first file on profile A)
   5. SEG-Y EBCDIC- and binary header files (called header and binary)
      • On PC Linux box
      • On pandora

Tape information

• Demux'ed data in SEG-Y format on Exabyte:
  • Exabyte drives:
    • On Linux PC box: Exabyte Corp. mod. 8505XLS
    • On "pandora": ........
  • Written with variable block size? YES
  • Media specs
    • Mfr.: Sony
    • Model QGD160M
    • Capacity: 7.0 GByte
    • Length: 160m

Tape archiving

• Field data, SEG-D-II format on 3480 tape cassettes: Stored at IFJ
• Demux'ed SEG-Y data: One set of Exabyte tapes, stored at NPD
• Tape Image Format (TIF) files on disk, one TIF-file for every field data tape, stored as follows:
  • Two sets of TIF-files stored on AIT tape, one set stored at IFJ, the other stored on external location.
  • One data set on PC harddisk (disk mounted in Linux PC box mentioned above).