# Jack Cohen

PhD university Courant Institute

Jack K. Cohen (1939-1996) was a mathematician, mathematical physicist, algorithm developer, and programmer. Jack published many papers in the field of wave propagation and seismic imaging. He was co-founder of the Center for Wave Phenomna and co-founder (with Shuki Ronen) of the Seismic Unix project, for which he received a Special Commendation (posthumously) from the SEG (with John Stockwell, Shuki Ronen, and Einar Kjartansson) in 2002.

## Memorial

by Norman Bleistein and John Stockwell

On 24 October 1996, the Colorado School of Mines community lost a great friend with the death of Jack K. Cohen. He was 56 years old.

Jack received his Ph.D. from Courant Institute of Mathematical Sciences, then spent 16 years at the University of Denver before joining the faculty at Mines in 1983. A founding member of the Center for Wave Phenomena at CSM, Jack left his immensely human and caring mark on students and colleagues within CWP, as well as on mathematicians and geophysicists around the world.

In the late 1970s, Jack co-authored two seminal papers characterizing the seismic inverse problem. These works established a mathematical basis for some of the algorithms used in seismic imaging. Thereafter, many more applied mathematicians and theoretical physicists became involved in research on this problem. Within five years of that work, the SEG Annual International Meeting hosted multiple sessions and workshops on the topics generated by these papers. Jack's skill as an innovator was not limited to the theoretical aspects of his work. Jack saw a need for a line of seismic processing software that would be freely available to everyone. Starting with a handful of codes written by members of the Stanford Exploration Project, with the help of Shuki Ronen, Jack created the Seismic Un*x, or SU package. This was long before the words e-mail, Internet, or free software entered the public lexicon. Today, the CWP/SU Seismic Un*x package is freely distributed on the Internet. The package now includes more than 380 individual modules which permit the user to perform many of the common seismic data manipulation tasks, as well as provide an environment for the development of new seismic software applications. Currently, there are more than 900 known installations of SU.\footnote{As of August 2000, there are more than 2000 verified installs, in 54 countries.} The package is used by petroleum exploration companies, government research facilities, and education institutions in more than 37 countries. Many users are well beyond the seismic exploration community.

Jack developed an expertise in symbolic mathematical languages, particularly {\it Mathematica}\footnote{$\mbox{\sf Mathematica\/}^{\tiny{TM}}$ is a trademark of Wolfram Research.} With a colleague, Frank Hagin, Jack co-authored five versions of a textbook integrating symbolic math software into an undergraduate calculus program. This interest led Jack to become editor of the Classroom Notes column in {\em The Mathematica Journal}.

Jack mastered the subject of wavelet transforms and provided the world community with free wavelet software packages written in the Mathematica language.

Jack also became interested in seismic anisotropy and contributed several important papers on this complicated subject. His work has provided a solid mathematical basis for some existing inversion methods for anisotropic media and stimulated new research in anisotropic moveout modeling and parameter estimation.

Jack's broad spectrum of interests spanned the subjects of classical literature, impressionist art, folk music, jazz, and Brazilian music. He was always ready to try new things, both scientific and nonscientific. He learned to ride a bicycle at age 37. He was an avid hiker and cross-country skier in his early years in Denver. Somewhat later, he started body-building, an activity that he maintained up to the time of his death.

Jack was a compassionate humanist, with a great love of mankind. He was popular in the classroom and known for having an off-beat sense of humor. At one of the first workshops on inversion at SEG's 1982 convention, a colleague asked him for a simple explanation of inversion compared to the more accepted migration of the geophysics community. Jack promptly proceeded to rattle off a list of the then-proponents of inversion and said, Don't you see? Inversion is Jewish migration!

He is survived by his wife Diane and daughter Mara. In his memory, Colorado School of Mines has established the Jack K. Cohen Memorial Fund for undergraduate scholarships. Donations may be sent to the Colorado School of Mines Foundation, 931 16th Street, Golden, CO, 80401.

## Special Commendation 2002 [1]

SEG in honoring the Center for Wave Phenomena, Department of Geophysics, Colorado School of Mines] for developing and freely disseminating the Seismic Unix package (SU). Many individuals have contributed and are contributing to SU. However, at this time, SEG wishes to particularly cite four individuals—John W. Stockwell Jr., Jack K. Cohen, Einar Kjartansson, and Joshua (Shuki) Ronen—for their exceptional contributions to this project. The success of SU is understated by the statistics but they are, nonetheless, impressive—the number of verified installs exceeds 3000, representing users in over 60 countries. The objectives of SEG to promote and foster the scientific interests of geophysics are clearly reflected by the SU project. SU is used by exploration geophysicists, earthquake seismologists, environmental engineers, and software developers. The spectrum of users includes oil companies, contractors, government researchers, and academics.

### Citation for SEG Special Commendation 2002

Contributed by Norman Bleistein and Ken Larner

Throughout the history of applied geophysics, advances have come in many forms, but mainly as new scientific ideas and technological innovations. Over the past 17 years, the geophysical research has benefited from a novel and powerful tool—initiated and developed within academia with contributions from researchers across the industry—that is neither a scientific idea nor simply a technological invention.

CWP/SU: Seismic Unix (SU) is an open software processing package developed at the Center for Wave Phenomena (CWP) within the Department of Geophysics, at the Colorado School of Mines (CSM). SU provides an instant research and processing environment, in the form of full source code, at no cost. It runs under all UNIX and UNIX-like operating systems, including Cygwin 32 on Microsoft Windows and Mac OS X on Macintosh. SU provides many modeling/data processing utilities, and a base of source code for development of new applications. In recent years, SU has become a vehicle for geophysicists to make their software available to the worldwide community.

Seismic Unix evolved from Jon Claerbout’s Seismic Exploration Project (SEP) at Stanford University in the late 1970s when graduate student Einar Kjartansson wrote a package called SY—12 programs in C to run under UNIX. This, in itself, was revolutionary, as contemporary industry practice was to write code in FORTRAN under the Vax VMS system. Code was also written by Stew Levin, Chuck Sword, and Claerbout himself. To this day Levin contributes importantly to SU. Einar continued to work on SY after joining the faculty at the University of Utah. He brought SY back to Stanford when he visited (as a faculty member) in 1984 and introduced graduate student Shuki Ronen to the concept. With Claerbout’s permission, Shuki brought SY to CSM in 1985 under a postdoctoral appointment at the Center for Wave Phenomena, then directed by Norman Bleistein and Jack Cohen.

In the same year Jack visited Texaco’s Houston Research Center to study how seismic processing was done in industry. Inspired by this experience, Jack and Shuki conceived a bold plan—to create a seismic processing line that would be used by everybody. Of course, in 1985 “everybody” consisted mainly of a handful of expert seismic programmers. The name was changed from SY to SU (standing simultaneously for Stanford University and Seismic Unix) and additional libraries and utilities were written. The package became an instant hit with CWP students, with contributions by almost every CWP member—notably Chris Liner, Brian Sumner, and Craig Artley.

In 1987 John Stockwell became CWP systems administrator and codeveloper of SU with Jack. In 1989, Dave Hale joined and made major contributions that expanded the package’s capabilities and portability. Prior to 1992, SU had been ported to only a handful of sites, mainly oil-company sponsors of CWP.

The first truly public release of SU was in September 1992, via an ftp site at CWP (several years before the World Wide Web was created). Stockwell has subsequently been the main contact for questions related to SU and its principal investigator since Cohen’s death in 1996.

The success of the SU project has been due in large part to John’s skill in helping users, his responsiveness to questions and comments, and his desire and commitment to continually improve the package. Since 1992, SU has been verifiably installed at more than 3000 sites (a gross underestimate of the total use of the package) in 60 countries.

With SU, the geophysics industry experienced a revolution in the way that it works with computer technology. Previously, software developed within universities was lost upon graduation of a student developer or commercialized. The revolution that SU brought was introducing free software to the geophysics community. A walk through the exposition during any SEG Annual Meeting will reveal SU in use on various computers, as well as its ubiquity in technical presentations and papers.

## References

1. Fred Hilterman (2002). ”2002 Awards Citations.” 2002 Awards Citations, 21(11), 1156-1168. doi: 10.1190/tle21111156.1