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?  bhedtopar outpar=binary.par < binary  What are the meanings of the header’s different fields?  sukeyword jobid  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.bin  To look at the content of data1.bin, use “b2a data1.asc”  How to add SU header to a binary file?  suaddhead ns=2000 data2.su  supaste ns=2000 head=data1.headers 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?  sugethwkey=tracl,tracr,offset,dt,ns < data.su | more  How to set the header words?  sushw key=dt a=2000 data2.out.su  How to edit header words?  suedit data.su