Hi,

depends on how many tape devices you have !
Generally seismic tapes are record oriented, is bloack may have differents length.

If you have 2 tape devices, tcopy is useful.
If not, you'll have to make a disk-copy, and then restore disk-copy to tape in the original set.
You'll have to know the structure of the tape (ie length of each block).
Using these informations you may use dd, or another program to copy to/from disk that take length into account.

There are 2 seismic formats that could deal with this:
SEG-RODE
TIF, tape interchange Format.