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Lesson 7

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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  1. Lesson 7 SU Data IO

  2. 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).

  3. 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.

  4. 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)

  5. 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

  6. 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

  7. 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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