SEGY ARCHIVE TAPE FORMAT:


THREE	SEGY TAPES CONSISTING OF FOR EACH COMPONENT 27 FIELD SHOTS CONTAINING
	444 SEISMOGRAMS EACH.

TAPE 1:	VERTICAL COMPONENT
TAPE 2:	HORIZONTAL-INLINE COMPONENT
TAPE 3:	HORIZONTAL-TRANSVERSE COMPONENT

=====================

EACH TAPE CONTAINS THE FOLLOWING:

Record	bytes	content
======	=====	=======
1	3200	Standard SEGY EBCDIC header
2	400	Standard SEGY binary header
3	80244	archive data trace of SHOTSEQ 1 trace 1
:	  "
11990	80244	archive data trace of SHOTSEQ 27 trace 444

SEE "segy_header" and "SP.description" for complete identification of
	data.  The SEGY trace headers in the archive tapes are properly filled
	according to the headers defined in "segy_header".  X-Y-Z geometry is
	not defined but can be using the SierraSeis geometry files provided
	in the archive tar files.

In general, each of the 27 field shots have 444 seismograms as follows:

SHOTSEQ  1-14:
		  1- 48  Chevron seismograms
		 49-128  Reftek seismograms
		129-444  Arco seismograms
SHOTSEQ 15-27:
		  1-278  Arco seismograms
		279-396  Reftek seismograms
		397-444  Chevron seismograms

=====================

TRACE LENGTHS:

The seismograms are all a uniform 80000 msec in length (20001 samples).
	Actual time lengths are as follows:
		60.000 sec Chevron
		80.000 sec Refteks
		40.000 sec Arco.

Sample rates of data are:
		0.004 sec Chevron
		0.004 sec Refteks
		0.002 sec Arco.

**********************
****** IMPORTANT NOTE:
**********************
	Because the Arco data had a 2 msec sampling rate and the other data
are all 4 msec, if the Arco data were made consistent, every other data
sample of Arco data would have to be thrown out.
	In order to archive the full 20001 samples of 2 msec data, all
samples are preserved in these archive tapes.  The sample rate is
defined to be 4 msec but in reality the rate is 2 msec.  The data was
not subsampled to get the 4 msec rate; the sample rate value was simply
redefined at 4 msec w/out any modification to the seismic data.
	Thus, in order to use the full set of data (Reftek+Chevron+Arco),
every other time sample of the Arco data must be thrown out in order to
get a true 4 msec sampling interval.  The header BOXTYPE can be used to
select the Arco data.  The IRIS-SEIS v1.5 compatible processor /RISCARCO
is provided in the archive tar files which will conduct the data subsampling
in order to create proper dimensionality.