Lesson 7
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Lesson 7. SU Data IO. SEGY format. SEG-Y: Society of Exploration Geophysicists Y format SEG publication: Digital Tape Standards Part I: 40 lines of text with 80 characters per line (3200 byte EBCDIC, Extended Binary Coded Decimal Interchange Code)

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Lesson 7

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Lesson 7

Lesson 7

SU Data IO


Segy format

SEGY format

  • SEG-Y: Society of Exploration Geophysicists Y format

    • SEG publication: Digital Tape Standards

  • Part I: 40 lines of text with 80 characters per line (3200 byte EBCDIC, Extended Binary Coded Decimal Interchange Code)

  • Part II: Binary header containing information about the tape reel (400 bytes)

  • Part III: Actual seismic traces, each trace has 240 bytes trace header, followed by the trace data, which are in IBM floating point format (NOT IEEE format).


Su format

SU format

  • SU data consist of SEGY traces only.

  • SEGY ebcdic and binary headers are not preserved.

  • Applying SU commands to SEGY data will not work.


Read segy and convert to su

Read SEGY and Convert to SU

  • segyread tape=data.sgy verbose=1 endian=0 | segyclean > data1.su

  • DO NOT put spaces around “=” !!!

  • You can put spaces around “|”, “>”, etc.

  • Little-endian .vs. big-endian

    • Well-known processor architectures that use the little-endian format: x86 (including x86-64)

    • Well-known processors that use the big-endian format include: IBM POWER

  • segyclean: zero out the optional trace header fields.

  • One common variation of SEGY format is to store the trace data in IEEE instead of IBM format. In this case, use the “conv=0” option (segyread tape=data.sgy verbose=1 endian=0 conv=0 | segyclean > data1.su)


Convert su to segy

Convert SU to SEGY

  • Prepare the SEGY EBCDIC header and binary hearder

    • segyhdrs < data.su

    • Generates two files: “binary” and “header”

  • How to read the EBCDIC header?

  • How to read the binary header?

    • bhedtoparoutpar=binary.par < binary

  • What are the meanings of the header’s different fields?

    • sukeywordjobid

  • segywrite tape=data.sgy verbose=1 bfile=binary hfile=header endian=0 < data.su


Su header manipulation

SU Header Manipulation

  • How to strip SU header?

    • sustrip head=data1.headers < data1.su > data1.bin

    • To look at the content of data1.bin, use “b2a < data1.bin> data1.asc”

  • How to add SU header to a binary file?

    • suaddhead ns=2000 < data1.bin > data2.su

    • supaste ns=2000 head=data1.headers < data1.bin > data3.su


Su header manipulation1

SU Header Manipulation

  • How to get the range of the header values?

    • surange < data.su

  • How to get the values of header words?

    • sugethwkey=tracl,tracr,offset,dt,ns < data.su | more

  • How to set the header words?

    • sushw key=dt a=2000 < data2.su > data2.out.su

  • How to edit header words?

    • sueditdata.su


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