Lesson 7

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# Lesson 7 - PowerPoint PPT Presentation

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

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)
• 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 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
• 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
• 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
• 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