I confess that, when I first met Ilya Tsvankin in 1986 in Moscow, I underestimated him severely.
     Of course, his remarkable abilities were immediately obvious, but I figured it would be 20 years or more before we honored him in this way. Instead, a short 10 years later, his fundamental contributions to the science and practice of exploration seismology have already elevated him into the illustrious company of the previous Kauffman medalists. It is worthwhile to recount here the turning points of this remarkable flowering of achievements.
     Ilya graduated from Moscow State University in 1982, a product of the long and illustrious Russian tradition in anisotropy studies. In 11 years at the Institute of Physics of the Earth, despite the unfavorable conditions, he published (mostly in Russian) many papers on exotic seismology; nongeometric, nonlinear, nonisotropic. Evidently, Ilya found conventional seismology too simple to provide any real challenge.
     In 1989, at the urging of his wise and beautiful wife, Olga Dashevskaya, Ilya and family emigrated to the U.S., during an interval when the window of immigration opportunity was temporarily open. At Amoco in those days, we had a postdoctoral program, a legacy of Gordon Greve's leadership as manager of Geophysical Research. When Ilya called me, upon his arrival in America, I was therefore able to respond with an offer of temporary employment. Thus was born one of the most satisfying collaborations, both
     personal and professional, of my career. With Ilya providing the theoretical muscle, we began to work out the implications, for exploration seismology, of the equations for weakly anisotropic media which had been reformulated in 1986.
     In 1992, the Colorado School of Mines conducted a worldwide search for an additional faculty member in exploration geophysics; their two top candidates both came from Amoco's Research Center in Tulsa. (Amoco was already in the midst of restructuring at the time, and we could not encourage them to stay.) Unable to chose between the two, CSM created a second position, and both Ilya and John Scales moved to Golden. There in the extraordinary environment that has grown at CSM since Ken Larner joined Norm Bleistein and Jack Cohen, Ilya's creative output has been simply sensational. Together with colleagues and students, he has since published 15 seminal papers on the analysis of seismic waves in anisotropic media and the practical processing of data from such media, with many more on the way (and already available to sponsors of the Center for Wave Phenomena at CSM).
     With this work, we are at last able to design and apply seismic-processing technology that relaxes one of our most serious approximations to real-world conditions. Our assumption of seismic isotropy was imposed upon us in the 1950s (despite the obvious contradiction with rock physics and the geometry of sedimentary layering) by the paucity of computing power in that day. As time went on, we became more and more entrenched in this paradigm, because the step to anisotropic processing seemed so large: it seemed that we needed to estimate four elastic moduli at every point in the earth, instead of one velocity.
     As the capability of our computers grew faster, we found ourselves computing ever more intensively, but with the wrong physical assumptions, and the inherent contradictions became ever more obvious. Perhaps the turning point came with the independent development of AVO. Driven (by the desire for AVO leverage) to acquire ever longer offsets, we all began to see nonhyperbolic moveout, and nonisotropic amplitude effects in our data. And, with the work of Ilya and colleagues around the world, we find that we do have practical analytic and processing tools to handle such data. Perhaps the most fundamental contribution is the understanding that we need only three parameters (cleverly chosen) for full anisotropic processing (of P-waves) in most situations, and only two if we content ourselves with time-domain kinematic processing. This level of complexity is something we can cope with. Azimuthal anisotropy is, of course, more complicated, but still tractable.
     Ilya's quiet leadership has been crucial throughout this development. Through his analytical skills and keen scientific insight, he always finds the best way to approach any problem, instinctively rejecting solutions not supported by the data. Through his collegial skills, he draws to himself talented students and colleagues, generating a synergistic school of thought in which the whole is greater than the sum of its parts. At CSM, he has found a fertile environment which energetically breeds ideas and
     nurtures talent. I expect that the exploration industry worldwide will benefit from this happy confluence for years to come.

      Leon Thomsen