OBS DATA HANDLING AND CONVERSION

The OBS data just downloaded upon recovery were checked for clock drifts and reorganized against the shot table. Two separate datasets in the SEG-Y IBM floating point big-endian format were provided: (a) continuous data and (b) shot ensembles (40s duration). The trace headers were also populated with clock drifts.

In order to convert the SEG-Y files into the SAC format [SAC (2006)],[Goldstein et al. (2003)], a shell/Perl [Perl (2006)] procedure was built that:

• converts the SEG-Y files into the Seismic Unix format [Cohen and Stockwell (2006)] (.su), since they were not easily readable by public domain routines; a partial reformat of the headers was necessary;
• dumps in the ascii format the .su files and produces the SAC Ascii datasets applying the clock drifts and the shot UTC absolute time including the milliseconds read by the shot table.

The procedure was used to produce SAC shot ensambles (60 s) and 1 hour continuous data. The SAC Ascii data were converted to binary using the SAC software for ease of handling and better I/O performance. The above routine will be able to produce the SAC binary straightforwardly with some updates and changes that are undergoing.

The code listings of the bash wrapper and of the perl procedure are presented hereinafter.

language=bash commentstyle= linewidth=15cm ../SRC/SEGY2SAC.SH

language=perl commentstyle= linewidth=15cm ../SRC/suascii2sac_all.pl