I attached the four PV-Wave files for reading and writing SU SEGY Files (and I 
am sure they will also run on IDL, though I never tested this by myself).
PV-Wave is a fourth generation graphics programming language which is very
convenient for analyzing large datasets. It is a commercial product of 
Visual Numerics Corporation at Boulder, Colorado.

				-Martin

;;=============================================================================
;;
;; Functions:  segy_write, segy_read, segy_header
;;
;; Author:     Martin Luethi, VAW, ETH Zurich, Switzerland
;;             luthi@vaw.baum.ethz.ch
;;
;; Date:       26. September 1996
;;
;; Purpose:    Write and read data files in SEGY format
;;             
;;             The SEGY format is a standard file format for seismic data.
;;             It consists mainly of headers containing all the information
;;             on a trace and a body with the measured seismic data. The
;;             data is stored in binary form.
;;
;;             The header fields are those defined by Seismic Unix which
;;             do not correspond in all detail to standard SEGY format
;;             (see the documentation of Seismic Unix for further details).
;;
;;             Seismic Unix is powerful free seismic software which is
;;             available via ftp from the Colorado School of Mines:
;;                   ftp.cwp.mines.edu. 
;;             Their homepage is located at 
;;                   http://www.cwp.mines.edu
