Gerard Schuster is currently a Professor of Geophysics at King Abdullah University Science and Technology (KAUST) and an adjunct Professor of Geophysics at University of Utah. He was the founder and director of the Utah Tomography and Modeling/Migration consortium from 1987 to 2009, and is now the co-director and founder of the Center for Fluid Modeling and Seismic Imaging at KAUST. Schuster helped pioneer seismic interferometry and its practical applications in applied geophysics, through his active research program and through his extensive publications, including his book "Seismic Interferometry" (Cambridge Press, 2009). He also has extensive experience in developing innovative migration and inversion methods for both exploration and earthquake seismology.
Gerard has an MS (1982) and a PhD (1984) from Columbia University and was a postdoctoral researcher there from 1984–1985. From 1985 to 2009 he was a Professor of Geophysics at University of Utah. He left Utah to start his current position as Professor of Geophysics at KAUST in 2009. He received a number of teaching and research awards while at University of Utah. He was editor of Geophysics from 2004–2005 and was awarded SEG's Virgil Kauffman Gold Medal in 2010 for his work in seismic interferometry.
SEG published Gerard's book Seismic Inversion in late 2017 and will be publishing his almost completed book Practical Machine Learning Methods in The Geosciences.
Spring 2013 SEG Distinguished Lecturer
Seismic interferometry and beyond: Harvesting signal from coherent noise
With the dwindling number of easy discoveries and ever increasing demand of energy resources, the oil and gas exploration industries are moving to less conventional plays, deeper water, and more difficult terrains. The attendant cost of drilling and extraction has prompted the energy and service companies to invest heavily in seismic data acquisition and processing to harvest as much illumination information as possible about the subsurface. Fortunately, the exploration geophysics community during the past decade has witnessed the parallel emergence of a new exploration geophysics topic – seismic interferometry. Seismic interferometry is a means by which unused events, often discarded as coherent noise, can be recombined to give usable signal for existing imaging algorithms. For example, multiple reflections can be recycled as virtual primaries that can illuminate larger portions of the subsurface than seen by the recorded primaries.
In this lecture I will introduce the concepts underlying seismic interferometry and present the workflows for its implementations and practical applications. I will show various ways to harvest useful signal from portions of the data normally considered as noise in conventional processing. I will use several examples to illustrate the practical benefits of interferometry and other multiple imaging methods: increased subsalt illumination by multiple reflections, tripling of the aperture of usable refraction arrivals by supervirtual interferometry, significant widening of the illumination zone of VSP data by transforming multiples into primaries, and reduction of the cost of imaging by multisource phase encoded migration and waveform inversion.
A recording of the lecture is available.
Please tell us a little bit about yourself (e.g., your educational and work experience, why you became geophysicist, etc.) As a child, I grew up in an amazing era: Sputnik, flying saucer hysteria, bad 1950s science fiction films, unregulated chemistry sets, affordable Edmund telescopes and microscopes, easy access to gunpowder recipes from Encyclopedia Brittanica, the dawn of lasers, satellites, transistors, atomic energy, etc. It didn't hurt to have dad's basement full of high-tech gizmos such as disassembled radios, oscilloscopes, and drawers of electronic parts. This witch's brew must have hit critical mass because by the time I was in 8th grade I knew I wanted to be a physicist, and understand some of the unbelievable things I had read, but could not understand, about relativity and quantum mechanics. I also grew to love chemistry in high school, and so majored in both physics and chemistry at Portland State University. I switched into geophysics in graduate school, mainly because of the job opportunities, and received my master's degree from the University of Houston. Immediately after that I worked for Arco as a data processor in Dallas and an interpreter in Houston for about 1.6 years. This gave me an opportunity to learn some of the wisdom and practical skills for exploration geophysics, and also fired my thirst to deeply understand imaging and deconvolution algorithms.
Fortunately, I was accepted by the perfect school for me, Columbia University, and studied under a great advisor, John Kuo. He gave me almost complete freedom to fill the gaps in my knowledge, and he also was in charge of a strong geophysical research consortium supported by more than a dozen oil companies. After my Columbia PhD in geophysics, I stayed an additional 1.5 years as a postdoc and then accepted an assistant professorship at the University of Utah in 1985.
I had an extremely rewarding career at the University of Utah from 1985 to 2009, and successfully developed the UTAM industrial consortium; its goal was to develop innovative modeling and imaging algorithms. I very much enjoyed the collegiality at UU, the wonderful support and opportunities for creative research, and the birth of my second family, my current and former graduate students.
In 2009, two perfect storms collided, the world financial crisis and my daughter's impending entrance into an expensive private college, which prompted my move to King Abdullah University of Science and Technology (KAUST) in Saudi Arabia. Overall, it has been quite an experience at KAUST, and the research support is unprecedented. The result is that the quality of my current students/postdocs and their output is at least equal to the best groups I worked with at UU. UTAM might have ended in 2010, but our new CSIM consortium easily picked up from where UTAM ended, and even more so. We are combining seismic imaging methods and Shuyu Sun's expertise on fluid modeling to develop improved methods for reservoir management.
Would you like to mention anything about your personal attributes that helped you achieve the professional status you enjoy today; was it self-belief, hard work, a mentor, or something else? I have a passion for physics and mathematics, a large curiosity coefficient, and, when I am keenly interested in something, I diligently dig until I get to the bottom of things. I also try to explain things in an easy to understand way, which is the only way I really understand something. Some inspiring classical geophysical heroes, to name a few, are Jon Claerbout, Paul Richards, Hiro Kanamori, Albert Tarantola, Bob Stolt, and Enders Robinson. Today's seismic savants in exploration geophysics include Yi Luo, John Etgen, Serge Fomel, Ilya Tsvankin, Dave Hale, Kees Wapenaar, Bill Harlan, Paul Fowler, Jean Virieux, Biondo Biondi, Bill Symes, Ross Hill, Joe Dellinger, George McMechan, Yu Zhang, Dirk Verschuur, G. Berkhout, Art Weglein, and dozens more. And a person who made a fundamental contribution to both exploration and earthquake science in the 1990s is Marta Woodward.
Why did you choose this lecture topic? Why is it important? Seismic interferometry is a method in which coherent noise can be harnessed to help better image the subsurface. For example, free-surface multiples are often considered to be enemies, and so geophysicists devote much time in their suppression. In my lecture I hope to convince you that they can help you, and sometime significantly enhance the illumination of the subsurface.
Could you tell us in a few sentences what your course objectives are? The objective is to explain the basic concepts of interferometry in an easy-to-understand manner. I will show examples of how coherent noise can be harnessed to improve the seismic imaging of the subsurface, either through interferometry or by tuning imaging conditions to the multiples.
The audience does not need to be convinced that when they drive home they should look out the front windshield (primary reflections from objects ahead of them) as well as their side and rearview mirrors (secondary reflections from cars behind and next to them). In the same way, I hope to convince the audience that the use of coherent multiples gives second and third extra views of the subsurface to sometimes dramatically improve their view of the subsurface.
Are there any more specific areas that you want to emphasize? I will show examples of how harnessing multiples can significantly enhance the subsurface illumination for VSP, OBS, and refraction data. The big teaser is the use of multiples for imaging below salt, something achieved with synthetic examples, but not yet with field data. This is an exciting frontier of geophysical research.
What do you hope people will have learned after they attend your lecture? How is it different from other lectures? Don't throw away multiples; these provide new opportunities for reducing exploration risk. This lecture is different in that it goes against conventional wisdom, and suggests that coherent noise can be a useful partner in exploration seismology.
You have quite a busy year ahead. Do you enjoy traveling? Will it be difficult to balance the tour with your work? I enjoy travel when I can see and interact with old friends, visit historically interesting areas of the world, and have the opportunity for outdoor adventures. I love to be surprised by the unexpected delight. KAUST is generous enough to give me the semester off after I doubled up on my teaching load in the fall of 2012.
Would you share with us one or two of your most exciting successes? Seeing students come up with unexpected breakthroughs: Yi Luo's amazing derivation of the wave-equation traveltime inversion formalism, successful waveform inversion of crosswell data by Changxi Zhou, unexpected success in inverting for 3D colluvial wedges by Dave Morey, Yonghe Sun's quasi-Monte Carlo migration, Hongchuan Sun's fast wavepath migration algorithm, Dave Sheley's reduced migration, Jianhua Yu's success with VSP interferometry, Jianxing Hu and Jianhua Yu's migration deconvolution, and Pawan and Ian's super-virtual interferometry. I am continually surprised to see the weak kittens in the litter sometimes grow rapidly to become roaring tigers by the time they graduate.
How about a couple of disappointments? I disappointed some of my colleagues and graduate students when I left for KAUST. Some students had to continue their work at UU under other advisors, which was a hardship in terms of delayed graduation. I injured my hip in 2002, so I could no longer play basketball, a lifelong passion, with the students after work.
What advice would you give to geophysics students and professionals just starting out in the industry? For MS students, pick a great school that offers broad training in geophysics and geology. For PhD students who want to specialize in seismic imaging, pick a school with a deeply knowledgeable advisor who will let you learn the fundamental physics and math of seismic and EM wave propagation. Unlike me, learn more about rock physics and geology; hopefully, your school will have its own seismic equipment, you can go out to the field and test ideas and enjoy the outdoors. Working for a few years in the industry prior to getting a PhD is a huge plus, and summer internships at oil companies are a close second. Learn parallel programming languages with C, C++, and/or Fortran. Read scientific journals, papers, and books outside of geophysics. Nature, Science, IEEE, SPIE, SIAM, and optics literature are great resources.
Virgil Kauffman Gold Medal
The Virgil Kauffman Gold Medal is awarded to Jerry Schuster “for pioneering work on seismic interferometry and imaging.” Schuster has long been interested both in exploiting new types of seismic data and in better utilization of the information contained in conventional data. He consequently extended the daylight imaging concept, originally derived by Jon Claerbout, into a mathematical framework for imaging, called interferometric imaging. The method combines cross-correlation with downward extrapolation and imaging (also a cross-correlation process), which makes his method less dependent on the availability of sources. Interferometric imaging offers new imaging opportunities, such as migration of multiples in data, even of transmitted waves, and identifying the location of unknown source locations from daylight data. His imaging of multiples, particularly from VSP data, is now widely accepted and has had a profound effect on expanding the imaging aperture for salt flank delineation. He integrated these results in the book Seismic Interferometry. Schuster’s contributions to seismic interferometry are seminal and the importance of his pioneering work will become even more important as seismic interferometry becomes widely accepted.
Biography Citation for the Virgil Kauffman Gold Medal Award
Contributed by Tamas Nemeth
A complete scientist significantly impacts many areas in his professional life, such as in basic research, the application of this research to real problems, and in teaching others about what he has learned. It is gratifying to see Professor Jerry Schuster honored this year with the Virgil Kauffman Gold Medal for his work on seismic interferometry, an effort that truly encompasses all these areas.
Jerry has long been interested in unconventional seismic data. His Utah Tomography and Modeling/Migration (UTAM) research consortium started in the late 1980s, and for a long time it focused primarily on crosswell seismic and VSP data. This focus yielded a different perspective on seismic data processing, since traditional hyperbolic-moveout-based processing methods did not work well in this acquisition environment. Jerry found that a combination of: (a) extracting information from all available wave modes, (b) compensating for limited illumination, (c) imaging and inverting directly in depth, and (d) calculating the image resolution addressed the needs for crosswell and VSP imaging. His experience in borehole geophysics led to the ingredients he would use later for his work in seismic interferometry.
In the mid-1990s, Jerry worked on an autocorrelation migration algorithm that he later extended to cross-correlation migration. His goal was to exploit the phase difference between the arrivals of different modes, for these phase differences could be indicative of subtle changes in the properties of the medium. Still, some problems persisted with cross-correlation migration, such as the presence of spurious ghost events generated by the cross-correlation of the input data. These issues were not resolved until he studied the daylight imaging concept derived by Jon Claerbout, who showed that the reflection response of a horizontally layered medium can be synthesized from the autocorrelation of its transmission response, and who understood that these events are a contribution to the integral beyond the evaluation surface. Jerry applied the correlation method not only to passive seismic data, but also to exploration data with active sources. He introduced the concept of interferometric imaging, which involves an integration of cross-correlation and migration. He supported his interferometric-imaging method by an elegant theory based on stationary phase analysis.
Why is seismic interferometry important? Compared with other disciplines, such as medical tomography or nondestructive materials testing, exploration geophysicists are very restricted in where they can place their sources and receivers. Seismic interferometry gives us some relief from our acquisition limitations by creating data as if we had sources or receivers in locations not in the original acquisition. As we understand interferometry today, it allows (a) the reconstruction of the Green’s function of the medium between “virtual” source-receiver locations where there is no direct measurement of the wavefield, or (b) obtaining depth images from the response of a single source, many receiver configuration, or (c) the reconstruction of the reflection response from many uncorrelated noise sources. Thus, the promise of seismic interferometry is to utilize more completely the existing data for the reconstruction of Earth properties, and to compensate for suboptimal acquisition geometries.
Jerry possesses a rare insight into the fundamental issues of geophysical problems and connects our problems with solutions found in other, seemingly unrelated fields. With his exceptional research creativity and old-fashioned scientific curiosity, he has been a fountain of ideas, conjectures, and exciting results throughout his career. He is unusual in his instinct for finding things that might work on a problem and his willingness to test them. And he still beats his students to the office every morning.