Leon Thomsen

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Leon Thomsen
Latest company Delta Geophysics
President year 2006
BSc Geophysics
PhD Geophysics
BSc university California Institute of Technology
PhD university Columbia University

Leon Thomsen holds degrees in Geophysics from Caltech (BS, 1964) and Columbia (PhD, 1969). His academic career began with postdoctoral appointments at CNRS in Paris, and at Caltech in Pasadena, followed by a tenured faculty appointment at the State University of New York at Binghamton (1972–1980). Thomsen's industrial career began in 1980, at Amoco's famous Tulsa Research Center. In 1995, he moved to Amoco's Worldwide Exploration Group in Houston, to help implement the ideas (e.g., AVO) that he had earlier helped to invent. After the 1999 merger, he served in BP's Exploration and Production Technology Group in Houston as Principal Geophysicist and Senior Advisor. Following retirement from BP in 2008, he remains professionally and scientifically active as Chief Scientist of Delta Geophysics, as Research Professor at the University of Houston, and as Visiting Scientist at Lawrence Berkeley National Laboratory.

Thomsen has led technical development in applied geophysics through innovation in vector seismics (polar anisotropy, azimuthal anisotropy, azimuthal AVO, converted waves, and Life-of-Field-Seismics); in pore-pressure prediction; and most recently in ISEM and anisotropic rock physics, through numerous SEG publications and presentations, and many patents.

Thomsen was an early recipient (1960–1964) of an SEG Scholarship. He received SEG's Fessenden Award in 1994. He served as SEG Distinguished Lecturer in 1997 and as SEG/EAGE Distinguished Instructor in 2002. He is an Honorary Member of GSH and of EAGE. He is a Foreign Member of the Russian Academy of Natural Sciences, and holder of their Kapitsa Medal.

Thomsen is especially noted for his seminal work in the topic of weak anisotropy. He was the 2006–2007 SEG President, and the 2017–2018 Chairman of the Board of SEAM.

SEG Maurice Ewing Medal 2020 [1]

With more than 4700 citations, Leon Thomsen’s landmark 1986 paper “Weak elastic anisotropy” is too well known to call for expounding, but it is relevant to say that this seminal piece of work heralded a new era in the seismic method and produced a quantum leap in the way velocity propagation began to be handled from that point onward. Until 1986, only a few geophysicists cared to take the anisotropy bull by the horns, and those few who did usually were confined to a mathematical ivory tower. Thomsen’s work brought anisotropy into the realm of the frontline geophysicist. In addition to his scientific achievements, Thomsen was the SEG Distinguished Lecturer for the fall of 1997, the SEG/EAGE Distinguished Instructor for 2002, and served as SEG president for the 2006–2007 term.

Biography Citation for the SEG Maurice Ewing Medal

by Peter Duncan

Everything about Leon Thomsen is larger than life. His presence is dominating, whether we are talking physical or technical. The first time I saw him was at an SEG Annual Meeting in Dallas in the mid-1990s. I was sitting in a small theater preparing to hear a presentation. The doorway was crowded but the crowd suddenly parted as this tall man, made even taller by his cowboy boots and pearl gray Stetson, strode into the room. I swear the chatter silenced as people reached out to greet Leon and be recognized in return.

Leon is being awarded the SEG Maurice Ewing Medal. To my mind, the recipient of such high recognition must be a technical leader in our community, one who has made notable contributions to our technology, not just once but continually over his or her career. Moreover, the medalist should be an active participant in our community for its greater good, taking part in the husbanding of our industry, our society, and our global community and giving unselfishly of his or her time and talents. It means leading in our professional pursuits, tutoring those who practice in our profession, and mentoring those who are coming along to replace us.

For his part, Leon has demonstrated an uncommon physical insight that led him to make important contributions to advancing our science. Furthermore, Leon has an uncommon skill at reducing his insights to an understandable form and a gift for communicating that knowledge and understanding to others. Leon has been and is now a professor of geophysics, currently at the University of Houston. Leon has also traveled around the globe many, many times teaching us about our science. Finally, Leon has held several high offices in the governance of SEG. In short, Leon meets or exceeds all the parameters of a worthy Ewing medalist. Dare I say that the fit is so good we might call these another set of “Thomsen parameters.”

Exploration geophysics is in Leon’s blood. His father, Erik, practiced geophysics at Amoco. A keen observational eye must run in the family, for Erik noticed in the 1950s a correlation between amplitude response and successful wells long before “bright spots” were talked about. But Leon was not about to follow in his father’s footsteps and headed to Caltech to study nuclear physics — on an SEG scholarship no less. There geophysics finally caught his attention, so much so that he went on to Columbia University to earn a PhD in the field. He had not yet succumbed to the exploration bug though, and after finishing at Lamont Earth Observatory, he took a teaching position at the State University of New York at Binghamton where he researched velocity anisotropy in crystals in the very deep (3000 km) earth — well beyond drilling depths.

He attained tenure at Binghamton, but exploration was indeed in his blood, and he landed in Tulsa in 1980 to work at Amoco Research under the leadership of Sven Treitel. Here, his inherited powers of observation enabled what came next. While visiting Denver to consult on some Santa Barbara Channel 2D seismic, he noted many amplitude mis-ties at line intersections. Leon immediately suggested this might be a result of anisotropy related to fractures and that while he “had no specific knowledge of the phenomenon,” he believed he could “figure it out.”

Figure it out he did over the next four weeks, resulting in the breakthrough paper on weak anisotropy that is still shaping our industry today and is the most cited paper published in Geophysics with more than 4700 citations. The insight earned him the SEG Reginald Fessenden Award in 1993, but he did not stop there. He went on to make fundamental contributions to the understanding and application of azimuthal AVO, pore pressure prediction, converted wave imaging, and, recently, controlled source electromagnetic techniques for petroleum exploration.

Leon has been generous in sharing his insights and knowledge. Not only has he authored more than 125 refereed papers and delivered countless lectures and seminars, he also has served as an SEG Distinguished Lecturer (1997) and the DISC instructor (2002). To appreciate what a great undertaking this last assignment was,I recommend you read his very enjoyable diary [2] from that arduous year. It will give you a real sense of Leon, his marvelous sense of humor, and his devotion to our science.

Of course, he has been a leader in the not-so- technical part of our community as well by being an editor, a committee chair, a director of SEG Global Inc., vice president in my 2003–2004 Executive Committee, SEG President (2006–2007), and chair of the board of directors of SEAM (2017–2018). To each office he has brought the same intensity, integrity, and insight that he has applied to his technical pursuits.

It should surprise no one that Leon has benefited from the dedicated support and guidance of his lifelong partner, omnipresent sidekick, and “executive manager” (his words not mine) Pat, who has been with him since they met while Leon was at Columbia. I know he feels that this medal is hers as much as his. My heartfelt congratulations to you both on behalf of all your friends, colleagues, and students.

"Leon Thomsen, 2005"

Biography for 2005 SEG President-Elect Candidacy

Leon Thomsen, principal geophysicist at BP, holds degrees in geophysics from Caltech (BS, 1964) and Columbia (PhD, 1969).[3] His academic career began with postdoctoral appointments at CNRS in Paris, and at Caltech, followed by tenured faculty appointments at the State University of New York at Binghamton (1972-80), and a sabbatical appointment at the Australian National University.

His industrial career began in 1980, at Amoco's Tulsa Research Center. In 1995, he moved to Amoco Worldwide Exploration in Houston, to help implement the ideas that he had earlier helped to invent. Following the 1999 merger, he serves in BP's Exploration and Production Technology Group in Houston.

Thomsen has led technical development through innovation in vector seismics: polar anisotropy, azimuthal anisotropy, azimuthal AVO, converted-waves, Life-of-Field-Seismics, and pore-pressure prediction, through numerous SEG publications and presentations, and patents.

Thomsen was an early recipient (1960-64) of an SEG scholarship. He has been a member of the Research Committee since 1987 (chairman, 1998-2000).

He received SEG's Fessenden Award in 1993. He was editor of SEG's Geophysical Developments Series (1994-98). He served as SEG Distinguished Lecturer in 1997 and as SEG/EAGE Distinguished Instructor in 2002. He is an honorary member of the Geophysical Society of Houston and of EAGE. He served SEG as vice president during 2003-04, and became an SEG Foundation Trustee Associate in 2004. He was appointed a foreign member of the Russian Academy of Natural Sciences, and given their Kapitsa Medal in 2004. He currently chairs the SEG Foundation Project Review Committee. [4]

2002 SEG/EAGE Distinguished Instructor Short Course

Understanding Seismic Anisotropy in Exploration and Exploitation

All rock masses are seismically anisotropic, but we generally ignore this in our seismic acquisition, processing, and interpretation. The anisotropy nonetheless does affect our data, in ways that limit the effectiveness with which we can use it, so long as we ignore it. In this short course, we will understand why this inconsistency between reality and practice has been so successful in the past, and why it will be less successful in the future, as we acquire better seismic data (especially including vector seismic data), and correspondingly higher expectations of it. We will further understand how we can modify our practice so as to more fully realize the potential inherent in our data, through algorithms, which recognize the fact of seismic anisotropy.

Course Outline

Section 1: Physical Principles

Section 2: P-Waves (Subsurface Imaging)

Section 3: P-Waves (Subsurface Physical Characterization)

Section 4: S-Waves

Section 5: C-Waves

Additional Resources

The accompanying textbook is available for purchase.[5]

A recording (online streaming version) of this course also is available.[6]

Biography Citation for the SEG Reginald Fessenden Award 1993

Contributed by Sven Treitel

In 1962, Thomas S. Kuhn published the first edition of his now classic study on the structure of scientific revolutions. He divided scientists into those working on routine problems (the puzzle solvers) and those who create the new scientific paradigms which project an existing discipline into novel and unexpected trajectories. Leon Thomsen definitely belongs to this second category. Along with a distinguished group of his academic and industrial peers, Leon has literally added a new dimension to exploration seismology. I refer, of course, to the emerging field of stress wave propagation in anisotropic media. The ideas have been around since the days of Love and before, but Leon reworked the entire theory into a form easily adaptable to the needs of the applied geophysicist. Thanks to these efforts, we are now beginning to infer fracture direction and fracture intensity from multicomponent recordings. The presence of fractures in the reservoir often controls its permeability, and is thus of vital economic importance. This work has inspired much recent interest in reservoir geophysics, a technology which brings explorationists into much closer working contact with the reservoir engineer. It is therefore no exaggeration to say that Leon is one of those directly responsible for the redirection of our efforts toward the geophysical delineation of the reservoir.

His anisotropy parameters "epsilon", "delta" and "gamma" have become household words in the technical literature - their use so universal that hardly anybody bothers to define them anymore. At such a juncture it is both fitting and appropriate that the SEG honor Leon Thomsen with the Reginald Fessenden Award.

Leon is a native of Tulsa, Oklahoma. His father, Erik Thomsen, had a distinguished career as an exploration geophysicist with Amoco. It was my privilege to know Erik years before I met his son, though Erik was happy to confine himself strictly to isotropic pursuits. Leon did his undergraduate work at Cal Tech, from where he graduated in geophysics in 1964. It is of interest to note that he was partially supported by an SEG scholarship - money well spent, on hindsight! He then entered graduate school at Columbia and received his Ph.D. from that august institution in 1969. After brief assignments at the Centre Nationale de la Recherche Scientifique in Paris, at Cal Tech in Pasadena, and at IBM in San Jose, California, he joined the faculty of the State University of New York at Binghamton. While there, he spent a sabbatical at the Australian National University in Canberra and was also a visitor at the Goddard Space Flight Center in New York.

In 1980, Leon made the decision to abandon the academic life. He moved back to his native Tulsa to join Amoco's Research Center. His earlier work in rock physics enabled him to view the seismogram from the perspective of a materials scientist and it was this fortuitous circumstance that enabled Leon to establish some of the earliest links between multicomponent seismic data and fracture patterns in the reservoir rock. Aided and stimulated by related work by his colleagues both within Amoco and elsewhere, Leon was thus able to lay the foundation for the use of seismic anisotropy in exploration work today.

It will come as no surprise that Leon has been and is a prolific publisher of his ideas. He is the author of several key publications, but perhaps the one that has had the greatest impact is his 1986 Geophysics paper entitled "Weak elastic anisotropy"[7], in which he defined the three anisotropy parameters now commonly associated with his name. Leon is a gifted teacher and a lucid writer - his prose is a pleasure to read. He has been a natural mentor for his younger colleagues at Amoco Research Center. Several industrial "postdocs" have worked with him in recent years, collaborations which have already produced important results. A good example is Leon's work with Dave Scott (now at University College, London) in the seismic prediction of pore pressure ahead of the drill. More recently, his research with Ilya Tsvankin (now at the Colorado School of Mines) has led to further insights into the behavior of anisotropic rocks.

Leon has been an active participant in professional affairs. He has been a loyal member of the SEG Research Committee, where all of us have learned that he is not afraid to speak his mind when the need arises. He is keenly aware of the predicament that science faces in both the energy industry and the country at large and he has spoken out forcefully in defense of exploration research.

It is said that behind every successful man there stands a woman, and Leon is no exception. His delightful wife, Pat, no doubt has done her share to contribute to Leon's success as a scientist. In Leon Thomsen, the Society of Exploration Geophysicists is rewarding one of the finest of our profession.

Honorable Mention (Geophysics) 1990

H. B. Lynn and L. A. Thomsen received 1990 Honorable Mention (Geophysics) for their paper Reflection shear-wave data collected near the principal Axes of Azimuthal anisotropy.[8]

Honorable Mention (Geophysics) 1988

Leon Thomsen received 1988 Honorable Mention (Geophysics) for his paper Reflection seismology over azimuthally anisotropic media.[9]

Thomsen Elected to National Academy of Engineering

The National Academy of Engineering (NAE) announced on 9 February 2022 that 111 new members and 22 international members have been elected, including two geophysicists, Leon Thomsen as a new member, and Öz Yilmaz as an international member. Election to the National Academy of Engineering is among the highest professional distinctions accorded to an engineer or applied scientist.

Thomsen’s induction is “for contributions to seismic anisotropy concepts that produced major advances in subsurface analysis.” Thomsen is well known in the field of geophysics for developing an appropriate approximation of complex anisotropy in the earth, namely, “Thomsen parameters” and “weak anisotropy” in seismic anisotropy in 1980s, which significantly impacted geophysical exploration over the last 40 years. He invented simplified concepts for polar anisotropy and azimuthal anisotropy when he worked at Amoco. He pioneered converted-wave imaging with seismic anisotropy in 1999, which has become the universal standard for analysis of converted waves. He also introduced anisotropic AVO analysis in 2013. In addition, Thomsen has been actively lecturing and teaching in the seismic industry and academia and leading the global efforts of developing new technologies through collaborated programs and academic societies. In 2002, SEG published his Distinguished Instructor Short Course book, Understanding Seismic Anisotropy in Exploration and Exploitation. The book was updated in 2014. Thomsen’s many honors and awards include the highest award from SEG, the Maurice Ewing Medal, in 2020. He served as SEG president for the 2006–2007 term and was the 2017–2018 Chairman of the Board of SEG Advanced Modeling Corporation (SEAM).


  1. 2020, SEG Honors and Awards Program, SEG Annual Meeting 2020, Houston
  2. https://library.seg.org/doi/10.1190/tle22050434.1
  3. CSEG Recorder, June 2002, Vo. 27, Number 6. http://csegrecorder.com/interviews/view/interview-with-leon-thomsen
  4. The Leading Edge, July 2005, Vo. 24, Number 7.
  5. https://doi.org/10.1190/1.9781560803270
  6. https://seg.org/shop/products/detail/1839
  7. Thomsen, L., 1986. Weak Elastic Anisotropy, Geophysics, 51(10), pp. 1954-1966.
  8. Lynn, H. B. and L. A. Thomsen (1990) Reflection shear-wave data collected near the principal Axes of Azimuthal anisotropy, GEOPHYSICS 55(2):147.
  9. Thomsen, L. (1988), Reflection seismology over azimuthally anisotropic media, GEOPHYSICS, 53(3):304.

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