Christopher L. Liner joined the faculty of the University of Houston Department of Earth and Atmospheric Sciences in January 2008 and is now professor and associate director of the Allied Geophysical Laboratories industrial consortium. He earned a bachelor of science degree in geology from the University of Arkansas in 1978, a master of science in geophysics from the University of Tulsa in 1980, and a Ph.D. in geophysics from the Center for Wave Phenomena at Colorado School of Mines in 1989. He began his career with Western Geophysical in London as a research geophysicist, followed by six years with Conoco. After working a year with Golden Geophysical, he served as a faculty member of the University of Tulsa Department of Geosciences from 1990 to 2004. From 2005 through 2007, Liner worked as research geophysicist with Saudi EXPEC Advanced Research Center, Dhahran, Saudi Arabia.
Liner's research interests include petroleum reservoir characterization and monitoring, CO2-sequestration geophysics, advanced seismic-interpretation methods, seismic data analysis and processing, near surface, anisotropy, and seismic wave propagation. He served as editor of Geophysics in 1999–2001 and contributing editor to World Oil in 2010 and is an editorial board member for the Journal of Seismic Exploration. Liner has written many technical papers, abstracts for scientific meetings, the "Seismos" column in The Leading Edge (since 1992), the "Seismos Blog," and the textbook Elements of 3D Seismology , now in its third edition. Liner is a member of SEG, AAPG, AGU, the Seismological Society of America, and the European Academy of Sciences. In 2011, he was named an honorary member of the Geophysical Society of Houston.
Biography for SEG President Elect Candidacy 2013
Chris L. Liner is a 35-year member of the SEG, was 1999–2001 Geophysics Editor, 2012 SEG DISC presenter (Elements of Seismic Dispersion: A Somewhat Practical Guide to Frequency-dependent Phenomena), and is currently on The Leading Edge Editorial Board. He is known to many SEG members through the long-standing occasional TLE column Seismos, the Seismos blog (over 45,000 visits since 2008), and as author of the book Elements of 3D Seismology. Chris' 2012 DISC was presented to over 1300 SEG members in 30 locations worldwide. He has authored many technical papers and scientific meeting abstracts, and the What's New in Exploration column in World Oil Magazine (2010). He is a member of AAPG, AGU, an Honorary Member of the Geophysical Society of Houston, and a corresponding member of the European Academy of Sciences.
Mirroring the SEG itself, Chris' background is both academic and industrial. Eleven years of business experience includes Western Geophysical, Conoco, Golden Geophysical, and Saudi Aramco. He has held faculty positions at the universities of Tulsa (1990–2004), Houston (2008–2012), and, currently, Arkansas. He now serves as the inaugural Maurice F. Storm Endowed Chair in Petroleum Geology in the Department of Geosciences, with research interest in carbonate outcrop and near-surface characterization, advanced seismic interpretation methods, seismic data analysis and processing, anisotropy, and seismic-wave propagation. Chris' education includes the University of Arkansas (BS in Geology), University of Tulsa (MS in Geophysics), and a PhD in Geophysics from the Colorado School of Mines working with the Center for Wave Phenomena.
While on the SEG Board of Directors and other committees, I have gained a working knowledge of how SEG fulfills the needs of individual geophysicists in the context of a growing, changing, and diverse membership. Having lectured in dozens of countries last year, and working in academia every day, I realize that SEG must strive to attract young, international members weaned on high technology.
These perspectives converge to define my priorities should I be elected. Ensuring SEG's scientific and commercial value to members and the larger community depends on our nimble adaptation to change. Because neither electronic networking nor distant and costly international conferences answer the needs of all members, I would encourage the resurgence of smaller regional meetings wherever the local SEG associate organization has legs to convene them. Continued cooperation with other international scientific societies is essential, I believe, to widen access to knowledge and opportunities for those we serve – a fine example being the new SEG/AAPG journal Interpretation.
SEG is a society we can all be proud of; for nearly 80 years it has been a financially transparent, apolitical, nonprofit organization. I would be proud to serve in a leadership role.
Elements of Seismic Dispersion: A somewhat practical guide to frequency-dependent phenomena
The classical meaning of the word dispersion is frequency-dependent velocity. Here we take a more general definition that includes not just wave speed but also interference, attenuation, anisotropy, reflection characteristics, and other aspects of seismic waves that show frequency dependence. At first impression, the topic seems self-evident: Of course everything is frequency dependent. Much of classical seismology and wave theory is nondispersive: the theory of P- and S-waves, Rayleigh waves in a half-space, geometric spreading, reflection and transmission coefficients, head waves, and so forth. Yet when we look at real data, strong dispersion abounds. This course is a survey of selected frequency-dependent phenomena that routinely are encountered in reflection-seismic data.
The following topics will be addressed in this course:
- Time and frequencyː The Fourier transform (FT) is a standard frequency-analysis tool, but it yields little information about combined time-frequency content. We will review the FT and its extension to short-time FT and continuous wavelet transform as representative examples of a broad class of time-frequency decomposition methods.
- Vibroseis harmonicsː The vibroseis source injects a long, slowly varying signal into the earth. We commonly find that new frequencies, or harmonics, that are not present in the sweep are present in the earth response. This interesting phenomenon is discussed in relation to a more familiar process, that of human hearing. Those harmonics are illustrative of a general property of nonlinear waves and interaction.
- Near surfaceː Velocity dispersion generally is considered not to be an issue in seismic data processing. This is nearly true for seismic body waves (P-, S-, and mode-converted) that propagate in the deep subsurface. In the near surface, however, velocities often show strong dispersion, and the description is considerably inaccurate. This is especially the case in marine shooting over shallow water where, even in the 10- to 100-Hz band, velocities are observed well above and below the speed of sound in water. This paradox arises because shallow water over an elastic earth forms a waveguide whose characteristics we will examine.
- Anisotropyː In this section, we consider seismic-velocity anisotropy and how it depends on frequency. We will restrict our comments here to velocity variation with respect to the vertical axis (VTI) in a horizontally layered earth. Of the sedimentary rock types, only shale is seen to be significantly anisotropic at the core, or intrinsic, scale. The question is how to calculate apparent anisotropic parameters of a layered medium as seen by very long waves. Backus (1962) solved this problem, and his method can be applied to standard full-wave sonic data. So where does dispersion come into all this? It is buried in the thorny question of the Backus averaging length.
- Attenuationː The distinction between intrinsic and apparent frequency-dependent seismic properties is nowhere greater than in attenuation. Constant Q and viscous theories of intrinsic attenuation are developed and compared with experimental intrinsic scattering-attenuation data. Intrinsic attenuation is found to be compatible only with the viscous theory, while constant Q yields a better explanation of scattering attenuation caused by layering.
- Interferenceː The preceding sections have explored frequency-dependent phenomena related to acquisition and wave propagation, effects that would be seen and dealt with on prestack data. Data processing will remove or correct for those effects and will be unseen by the interpreter. However, dispersion effects (in our broad meaning) remain in the realm of final imaged data. First and foremost is the fundamental, unavoidable phenomenon of interference. We will discuss selected topics in this broad field, including the thin bed, bandwidth effect on reflectivity, single-frequency isolation, and reflection from a vertical transition zone.
- Biot reflectionː Many of the dispersion effects discussed previously contain information about the subsurface, but none as direct and important as the problem of reflectivity dispersion resulting from a poroelastic contact in the earth. We will review the nature of body waves in porous media and the characteristics of Biot reflection from an isolated interface and will end with an introduction to Biot reflections in layered porous media.
After completing this short course, the participant should be able toː
- gain a broad understanding of dispersive phenomena and related investigation tools
- understand the fundamental difference between intrinsic and apparent dispersion phenomena
- improve knowledge of the reflection process beyond the classic model
- provide an appreciation of historical development and a deep guide to the literature for self-study
The accompanying textbook is available for purchase.
A recording (online streaming version) of this course also is available.