“Seismic imaging would not be possible without a solid mathematical understanding of seismic waves"

An interview with Gary Margrave

Coordinated by: Satinder Chopra | Photos courtesy: Penny Colton
Gary Margrave

Gary Margrave is Professor of Geophysics and Mathematics, Department of Geoscience at the University of Calgary, and Director of CREWES Program. Before joining the U of C in 1995, he spent fifteen years with Chevron Corporation where he held a variety of geophysical positions. Gary led Chevron Canada’s first 3-D seismic processing. He was also a leading teacher in Chevron’s training program – developing and teaching courses in migration, deconvolution, seismic velocity modeling and geophysical programming.

Gary obtained his Ph.D. in geophysics from the University of Alberta in 1981. His expertise is in the research, teaching and application of exploration seismology, including seismic data processing, migration and mathematical signal theory. His research interests include signal band estimation, seismic attenuation, deconvolution, imaging and seismic wave propagation, though most people recognize him as an expert in Gabor Deconvolution and migration.

In 2001, Gary was appointed as the U of C Site Director for the Pacific Institute for the Mathematical Sciences or PIMS.

Gary conducts a course on seismic signal processing on the CSEG platform. He is a well-published author who has presented famously at Conventions and workshops, and has won several Best Paper awards for his presentations at the CSEG Conventions and luncheons. He has written a book on Geophysical Exercises in MATLAB, which he hopes to publish with the SEG soon. Gary is also a member of the RECORDER Committee.

In a candid talk, Gary reveals his point of view on different questions posed to him. Following are the excerpts from his interview.

Please tell us about your educational background and your work experience?

I have always been interested in the hard sciences and originally enrolled in physics at the University of Utah as an undergraduate. I completed both my B.Sc. and M.Sc. there in physics, studying general relativity for my masters. Then, in 1976 I transferred to the UofA to pursue a PhD in geophysics, which I completed in 1981. My field of study was plate tectonics and I did field work in Peru where we collected microgeodetic survey data over an active fault. For my thesis, I inverted the data to estimate earth strains. Following this I joined Chevron Canada in 1980 at which time I knew nearly nothing about exploration seismology. Fortunately, Chevron had an excellent training program and I rapidly became familiar with seismic imaging and essentially fell in love with the subject. In 1981 I was transferred to Chevron’s Houston office where I was involved in special projects and also where I developed and taught Chevron’s first corporate course in migration. I returned to Canada in 1988 and, then in 1995, left Chevron to join the CREWES project as a staff researcher. Since then I've applied myself in the academic world, gaining an academic appointment in 1998, tenure in 2004, and promotion to full professor of geophysics in 2006. Presently I am also an adjunct professor in mathematics and Director of the CREWES project.

Were you always interested in science? How is it that you decided to pursue a career in science?

I have been interested in science for all my life. Some of my earliest memories are of learning to read at 5 or so and immediately reading children’s books on the earth, volcanoes, and the stars. My fascination with astronomy blossomed in high school when I built my own Newtonian telescope including grinding my own mirror. My pursuit of science has been so single minded that I have rarely had any doubt about what my career path should be.

How come you decided to come to University of Alberta for your Ph.D.?

I was studying general relativity at the University of Utah and had a crisis of confidence, doubting that I could survive in such a non-applied field. After some study, I decided that geophysics offered the right combination of practicality and hard physics problems. The U of A was especially attractive to me because geophysics was part of the physics department there and not directly allied with geology. I like to think that I do geoPHYSICS and not GEOphysics.

What kind of research work did you do for your Ph.D.?

As I mentioned previously, my work involved studying plate tectonics and inverting some geodetic survey data for earth strains. I also spent a great deal of time studying elasticity theory and learning methods of computing stress and strain in complex bodies. While I did not do anything related to exploration seismology, and barely knew what a wiggle trace is, I learned a lot of mathematical physics and these skills have turned out to be very useful in my career in seismic imaging.

So you worked for Chevron in the US and Canada for about 15 years and then decided to come to U of C. What prompted you to decide on this?

I felt that I had come to the end of my possible career path at Chevron. I wanted to live in Calgary and also to be involved with research and this did not fit with Chevron’s corporate structure. I learned a great deal while at Chevron and met many fascinating people, some of whom are friends to this day. I’m very grateful for the experience and training that I received at Chevron. However, after 15 years, I felt I was stagnating and needed a challenge, and I really wanted to try academia. Fortunately for me, CREWES provided me with an opportunity to do just that. I had met Rob Stewart at Chevron when he was also employed there. Rob was willing to give me a chance with CREWES and I was ready to take that risky step.

Gary and Satinder

What do you have to say about how your career has shaped up?

I’m very happy with the way things have worked out. My industry experience is excellent background for my present University job. It allows me to understand research issues from the practical perspective of industry needs and helps to guide my choice of research topics. What I like the most about my present situation is the interaction with students, especially graduate students. I have been extremely fortunate to have worked with a superb group of students since coming to the U of C in 1995 and this is very rewarding. I feel that this is my chance to do something truly useful and meaningful by helping young people learn an exciting and challenging field and get started on their careers.

Gary, I have found you to be very quiet whenever I have met you at conferences or luncheons. If I were to ask you to list three of your qualities that would reflect Gary’s personality, what would they be?

Well, that’s a bit surprising to hear, but I suppose I can understand your perspective. I’m no expert in personalities or human relations so I’m not sure how to respond. I suppose I could say that I’m a contemplative person who is driven to understand the universe as it is today and how it evolved. I like humor and often try to employ jokes and puns in my talks. Perhaps you might remember some of that in my CSEG luncheon presentations. As for a third quality, perhaps I will just say that I strive to be open to any and all ideas and sometimes that has helped me to see creative solutions. In a related sense, I also strive to view situations from the perspective of others. This can be a very helpful thing to do when teaching something as complex as mathematics.

Please tell us about some of your professional life teaching experiences at U of C?

Teaching at the University is a completely different experience from teaching in industry, and I prefer the former. Industry teaching has the advantage of a mature audience who are generally very interested and motivated. However, I find the temporally compressed nature of the teaching to be too intense for me as an instructor – it’s exhausting – and the information flow is too rapid for the students to learn effectively. At the university, a course is spread out over 3 months and there is time to think and study and hopefully digest the complex subject matter. Since coming to the University, I've been teaching data processing and I present it from what the students feel is a very mathematical perspective. However, I feel that this perspective is required to truly understand the techniques and to really hope to apply them or advance them in a creative way. So, I make no apologies for the math but I do try very hard to help the students learn. Also, I am very intent on helping to create a mathematical geophysics stream within the U of C’s geophysics program.

You specialize in digital signal processing and seismic imaging and you also teach some courses in mathematics? Why this special focus on these areas?

These subjects are at the heart of the seismic method. When you stand back for a moment and think about what exploration seismology purports to do it is truly remarkable. With seismic images we are literally able to see through kilometres of solid rock to map 3D structures with incredible detail. Seismic imaging would not be possible without a solid mathematical understanding of seismic waves and the estimation of earth properties through inverse theory. Inverse theory is the field that deals with estimating the earth properties that give rise to the data that we measure. The subject is so deep and rich that I feel it will pose challenging and fascinating problems for many lifetimes to come. I think the way forward is to advance our mathematical understanding of seismic waves and then to harness the best computational resources to apply to the inverse problem. I have found a great deal of interest in our problems in the mathematics community and I enjoy helping mathematicians learn enough geophysics to focus their skills on our problems. In fact, just stating a geophysics problem with sufficient clarity and rigor to satisfy a mathematician is rewarding by itself.

What according to you is your most important contribution to geophysics? What career accomplishments are you most proud of?

I am a bit of puritan when it comes to talking about pride. Perhaps I will substitute “satisfaction” for “pride”. As for my personal work, I have found the development of useful data processing algorithms to give satisfaction. I have specialized in the application on nonstationary filters to seismic imaging. This has resulted in Gabor deconvolution, which I think is a very powerful method with lots yet to understand, and also in some interesting developments in migration. I also enjoy software creation and have written quite a few codes that get widespread use. As for the career accomplishments that seem meaningful, the foremost has to be my graduate students. What a fine bunch of people they are and it thrills me to see them find success in their careers. Whatever I have achieved will pale in comparison to their collective output. I am still in touch with many former students and I take great pleasure in hearing about their accomplishments.

You are now working as a Professor at the U of C and Director of CREWES project. What personal and professional vision are you now working towards?

Recent developments at the University, especially the departure of Rob Stewart, have forced me to focus more on administrative tasks that ever before. At this time CREWES is a vibrant structure, full of interesting people who are all motivated to address our collective research goals. We also have access to more in the way of infrastructure – computers, seismic equipment, software – than ever before. So we are well poised to continue to make an impact and to deliver value back to the companies and taxpayers who support us. At the same time, we are faced with the need to renew our major NSERC grant and such a renewal is never a sure thing. This requires that we develop a research plan for the next five years and so requires that we do some collective prognosticating about where things are going. This is all good, and the exercise will certainly benefit us in the long run, but it has proven to be a demanding task.

During your Chevron years you have worked on software development and presentation of results during intercompany presentations? Do you think that was a good training ground for your later research?

Chevron was a superb training ground for me. In 1981, when I moved to Houston, I had the good fortune to come under the influence of their senior migration expert Vern Herbert. Vern was a Canadian who had worked in Calgary for many years, independently discovering the FFT in 1960, and at the time I met him, he had just completed development of a 3D post-stack depth migration. In 1981 this was a big thing and I believe that Chevron was the first in the industry to bring 3D depth migration into common use. I learned a lot from Vern, and became convinced that the Fourier techniques he was using in migration were actually very advanced mathematics even though Vern did not think of them that way. He thought algorithmically, in code if you like, and knew that what he was doing was “right” but it was difficult for him to convince others. For awhile, my job was to tell the rest of the corporation how Vern’s method worked. Later when I came to the University I had learned to write down Vern’s method mathematically and was driven to discover if such things were known to academics. Eventually I learned that Vern’s method was something called a Fourier Integral Operator and that Vern was far ahead of the academics in terms of applications. In fact, most are astonished when I tell them the theory has been applied and that it was actually applied before it was a published theory in the mathematical literature. This is a good illustration of why exploration geophysics and seismic imaging in particular are such fascinating fields to work in. The problems posed by seismic imaging are among the most challenging known and the drivers pushing us for answers are not just curiosity but also economic necessity. Vern Herbert was pushed by Chevron’s economic need to be a successful business and this could not wait for the discovery of advanced mathematics by established academics. I believe that there are many similar examples in the history of our profession and I would love to hear of them.

Are there other areas of geophysics that fascinate you in particular but you have not been able to get working in them?

I have always enjoyed the study of plate tectonics, particularly as it relates to mountain building. As a graduate student at the University of Alberta, I made some initial forays into the computation of stress and the prediction of failure (i.e. faulting) for complicated regimes. I like to think that in at least one parallel universe that is what I am doing today.

What are the directions in which the future R & D worldwide is focused in our industry? What is your impression about (a) the important developments that people can expect in geophysics in the near future (b) anything path breaking that we can expect that would revolutionize things, after the 3D seismic adoption in the 1980s and becoming a routine in early 1990s.

I believe that the future of seismic imaging will be one of increased mathematical complexity and computational load as demanded by the need for higher resolution images and more accurate predictions of rock and fluid properties. The widening understanding of the connection between seismic migration and more general inverse scattering theories allows us to envision entirely new and more powerful imaging methods, such as those using multiples as signal and nonlinear methods capable of much greater resolution. The need for greater resolution means that we will also continue to see improvements in acquisition, such as more channels and more bitsper- sample. I believe that the use of multicomponent geophones will continue to grow as we develop better ways to extract value from the additional horizontal components. The increased need for optimal reservoir exploitation also means that seismic imaging will move more and more into time-lapse setting which places increased importance upon repeatability. This is a tremendous challenge to acquisition and; assuming the perfect repeatability is not possible, also a challenge to data processing.

You have written and published quite a few research papers. Ever thought of writing a book also? I do know that you were working on some MATLAB exercises in Geophysics. Could you share with us your writing experiences? When can we expect your book to be ready for publication?

I've actually written two documents that are nearly “books”. One is the course notes that I use in teaching data processing and the other is a text that is freely available from the CREWES website called “Numerical Methods of Exploration Seismology”. The latter is intended to describe the use of my Matlab toolbox which is also free. I regularly receive emails from around the world sent by people who are either studying my Matlab book or teaching from it.

What is your impression about the current state of the Canadian universities, in general and then with respect to Geophysics in particular? How do they compare with other North American and European universities? You may also like to include in terms of the funding, problem-oriented research, dearth or abundance of students, etc.

I much prefer the Canadian method of funding research in science to the American system. Here NSERC grants are a reasonable expectation for any scientist who is active and publishing. Although small, these grants give a great deal of personal freedom to attend those meetings that are important and purchase the equipment that each researcher feels is needed. As for teaching at the University I've already commented to some degree but let me say here that I believe that the University of Calgary has been continually and systematically underfunded by the province. This has resulted in unreasonably large classes held in overcrowded facilities and this degrades the learning experience. At present, the University of Calgary has the strongest applied geophysics program in Canada and one of the very best in the world. An indication of this was seen at this year’s SEG where two of our graduate students, Jason McCrank and Maria Quejada, won a Jeopardy-like challenge competition against students from around the world. I also regularly hear that our graduate students are able to compete with the best in any other setting. This has been done inspite of provincial underfunding and a key factor here has been the industry support that we have received through the CREWES project.

What sets University of Calgary apart from other universities in Canada? What is it that would attract students to come here? What is the focus of research here?

From a geophysics perspective, I think the key attractions are the chance to live in a beautiful western city near such extreme natural beauty; to be involved in the most active concentration of geophysical expertise in the world (i.e. our downtown community); and to be part of one of the world’s best geophysics research groups by joining CREWES. We have a tremendous concentration of expertise and opportunity here and the chance and the challenge to do something really exciting and really beneficial to our society. My main concern right now is that we do not seem to have enough Canadian students entering our graduate program. We are presently working to encourage more of our undergraduates to consider our graduate school before entering the professional workforce.

You have won many awards for the research work that you have done. How does it feel?

I rarely think about awards. I prefer to look to the future and to the exciting problems and challenges that it holds.

What other interests do you have?

I have always been interested in history and read widely on the subject. The history of mathematics and science are special favorites. Another subject that I cannot seem to read or discuss enough is the potential unification of science and religion. That sentence might seem like nonsense to many of your readers but I believe that such a unification is both possible and essential for our collective future. As Frank Tipler puts it, either there is a view of God and religion that is in complete accord with science or religion is false.

What would be your message for young geophysicists entering our profession?

Our need for hydrocarbon resources will not disappear in my lifetime or yours. The science of finding these reserves and monitoring their extraction is where applied geophysics is essential and this is a broad and complex task. Come and join us if you like to understand the physical world, if you are creative and like to solve problems, and if your want to feel that your work makes a meaningful contribution to society. You can never learn too much physics or too much mathematics. Be prepared for a lifetime of learning and be ready to take part in an active community of talented professionals.


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