[Seisunix] asking for SEG-Y rev1 and rev2 datasets

David Forel davidforel at yahoo.com
Thu Feb 4 20:14:20 CET 2021


Hi Everyone -
I am writing to ask a favor.  Do you have any small (fit into an e-mail or you might have a DropBox link) SEG-Y rev1 and rev2 datasets?

I am working on a YouTube video about importing from SEG-Y to SU ... and ... exporting from SU to SEG-Y.  I am asking for these datasets so I can test "segyread" as I prepare the video and accompanying PDF documentation.

 (My YouTube channel is "Seismic Rocks" and my web site is www.SeismicRocks.com)
I am pretty sure SU cannot handle an input SEG-Y file that has multiple trace headers (rev2).  I don't see any parameters in "segyread" for handling multiple trace headers; although I admit, my C code knowledge is rusty.

However, I think SU might be able to import a rev1 file, a SEG-Y file that has one or more 3200-byte text blocks after the 400-byte binary header and before the first 240-byte trace header (see the attached figure).  The reason I think this import might work is because "segyread" has parameter xfile (file to store extended text block), a parameter that appears similar to parameters hfile and bfile.

I would be grateful if you can send me small SEG-Y rev1 and rev2 files to test for my video.

Thank you!David. . . . . . . . . . . . . .

Note: Information relevant to rev1 is in the 400-byte binary header:

The SEG-Y document counts bytes in the 400-byte binary header as a continuation of the 3200-byte text header. That means the first four bytes of the binary header are numbered 3201-3204 in the document. Below, I put that numbering first, then numbering that starts at 1 (one) in square brackets ([ ]). 

bytes 3501-3502 [301-302]: SEG-Y format revision number.
bytes 3505-3506 [305-306]: Number of 3200-byte extended textual file header records following the binary header. . . . . . . . . . . . . . 

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