Unix Commands and Concepts
The following table lists essential Unix commands.
This chapter explains fundamental Unix commands that are necessary for understanding later scripts. It will be helpful if you know elementary Unix commands. Books titled “Teach Yourself Unix” have excellent, simple, early chapters that give the basics. Also, by surfing the web, you can find universities that have good tutorial sites.
The following file name suffixes are used throughout this Primer.
.sh shell script
.scr shell script that launches a .sh shell script
.su binary seismic data
.dat binary data, not seismic data
.eps image file formatted as Encapsulated Postscript (EPS)
.txt ASCII data file
The SU seismic data format is based on, but is not identical to, the binary format called SEG-Y. SEG-Y was defined by the Society of Exploration Geophysicists (SEG) and has become an industry standard format for seismic data exchange.
The following file types can be printed directly to the screen by the cat and more commands: .sh, .scr, .txt.
We do not explain the following advanced Unix concepts in detail. Their usage will be made clear by the way we use them in later scripts.
The following Unix commands are not complete. These are merely a selection of commands that we consider helpful for your understanding and reproduction of the processing in this Primer.
Remember that Unix is case sensitive. That is, suplane is not the same as Suplane.
To start the Bourne shell interpreter, the first line of any script we make must be:
Figures & Tables
Our objective is to introduce you to the fundamentals of seismic data processing with a learn-by-doing approach. We do this with Seismic Un*x (SU), a free software package maintained and distributed by the Center for Wave Phenomena (CWP) at the Colorado School of Mines (CSM). At the outset, we want to express our gratitude to John Stockwell of the CWP for his expert counsel.
SU runs on several operating systems, including Unix, Microsoft Windows, and Apple Macintosh. However, we discuss SU only on Unix.
Detailed discussion of wave propagation, convolution, cross- and auto-correlation, Fourier transforms, semblance, and migration are too advanced for this Primer. Instead, we suggest you refer to other publications of the Society of Exploration Geophysicists, such as “Digital Processing of Geophysical Data – A Review” by Roy O. Lindseth and one of the two books by Ozdogan Yilmaz: “Seismic Data Processing,” 1987 and “Seismic Data Analysis,” 2001.
Our goal is to give you the experience and tools to continue exploring the concepts of seismic data processing on your own.
This Primer covers all processing steps necessary to produce a time migrated section from a 2-D seismic line. We use three sources of input data:
Synthetic data generated by SU;
Real shot gathers from the Oz Yilmaz collection at the Colorado School of Mines (ftp://ftp.cwp.mines.edu/pub/data); and
Real 2-D marine lines provided courtesy of Prof. Greg Moore of the University of Hawaii: the “Nankai” data set and the “Taiwan” data set.
The University of Texas, the University of Tulsa, and the University of Tokyo collected the Nankai data. The U.S. National Science Foundation and the government of Japan funded acquisition of the Nankai data.
The University of Hawaii, San Jose State University, and National Taiwan University collected the Taiwan data. The U.S. National Science Foundation and the National Science Council of Taiwan funded acquisition of the Taiwan data.
Chapters 1–3 introduce the Unix system and Seismic Un*x.
Chapters 4–5 build three simple models (complexity slowly increases) and acquire a 2-D line over each model. (These chapters may be skipped if you are only interested in processing.)
Chapters 6–9 build a model based on the previous three, acquire a 2-D line over that model, and process the line through migration.
Chapters 10–11 start with a real 2-D seismic line of shot gathers (Nankai) and process it through migration.
Chapters 12–13 and 15–16 start with a real 2-D line of shot gathers (Taiwan) and process it through migration.