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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

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?
    • sugethw key=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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