Sam Gray has a long and distinguished record of publications addressing not only the theoretical side of wave propagation and migration theory (and other topics). But, significantly, along with these contributions, his work has also focused on the practical side of imaging. His most recent contributions have contributed to our understanding of beam migration and other true-amplitude imaging issues.
Biography Citation for the Reginald Fessenden Award
Sam received his Ph.D. in mathematics at the University of Denver in 1978. Sam’s style was established from the get-go: cut-off shorts, wrinkled tees, long hair, tennis with a wood racket at the local park, and a bike with too few gears and a steep frame. He was a fine colleague to his fellow graduate students; a source of humor and camaraderie. During this time, he met his wife Julie and they married at the Evans Memorial Chapel on the campus of the University of Denver. Sam and Julie have two children, Christopher and Catherine.
Sam’s career in exploration geophysics began in 1982 when he joined Amoco. He was among the last in a cohort of gifted scientists hired by Amoco’s Tulsa Geophysical Research Division. Here he first became interested in the 1D seismic inverse problem, a topic made popular by earlier work of Geza Kunetz at CGG in France. After some time, he became increasingly attracted to a seismic imaging project conducted by Dan Whitmore in a group run by Ken Kelly. Here Sam’s deep mathematical insights began to bear fruit: early work with poststack Kirchhoff time migration was successively followed by Kirchhoff poststack depth migration, and these already established techniques then led him to their prestack counterparts.
Next Sam tackled a problem that had defied the efforts of the best imagers in the trade: to map not only the steepest portion of a salt dome flank, but also to obtain pictures of the salt overhang from below. He was among the first, if not the first, who managed to achieve this impressive feat by the use of turning rays, whose computer implementation he achieved by remarkably clever programming trickery. Sam’s earliest imaging work at Amoco soon found widespread application within the company because of a close collaboration with Davis Ratcliff, who was then working in Amoco’s Houston office. While Sam developed the ideas and the software, Davis became its masterful salesman; the two made quite a team.
A clever contribution of Sam’s was his solution of the operator aliasing problem in Kirchhoff migration. It arises when the migration swings events out to very steep dips; the high-frequency components become under-sampled on the migration grid, and a noisy image results. Use of sampling theory led to a migration operator that produced cleaner images. This trick is now universally applied to Kirchhoff migration.
By 1994 it became clear that Amoco’s Research Center had entered a period of decline; Sam requested a transfer to Amoco Canada in Calgary, where he continued his imaging research until Amoco was merged into BP.
Sam joined Veritas, now part of CGGVeritas, in Calgary in 1999, where he has remained ever since. He continued his work in depth imaging, velocity estimation and seismic modeling, both in classic acoustic models and in anisotropic elastic models of the Earth. He is also part of a group in the company who are intent on introducing “true-amplitude” adjustments in a ray-theoretic sense to various migration techniques, including Gaussian beam and reverse time migration. He is much in demand for expository presentations and papers, sharing his insights on the imaging aspects of seismic data processing in which he is a recognized expert. A paper he co-authored received a Best Paper award in Geophysics (1999), with two others cited for honorable mention, and he received an award for Best Paper presented at the SEG Annual Meeting in 2004. He also co-authored a paper that received a Best Paper Award in The Leading Edge this year. Sam remains active in research and development of modeling and migration methods, collaborating with colleagues both in and outside of CGGVeritas. The variety of his co-authors is an indication of the breadth of his interests and capabilities. His current title is Chief Scientist, a clear indication of his stature within the company, and more broadly within the industry.
SEG Best Paper in Geophysics Award 1999
- Gray, S. H. and G. E. Murphy (1999), Manual seismic reflection tomography, Geophysics 64(5):1546.