# Andrew Curtis

**Andrew Curtis** holds the chair of mathematical geoscience at
the University of Edinburgh. Over the last 12 years, Andrew
has published a succession of highly influential papers in the area
of seismic interferometry and theoretical seismology, for which
he is recognized through the Reginald Fessenden Award.

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## SEG Reginald Fessenden Award 2017

Andrew Curtis is recommended as the 2017 recipient of the Reginald Fessenden Award for his establishment of the concepts of seismic interferometry. Curtis’s work has been used to construct earthquake seismograms in deep ocean waters where no seismometers have been deployed. This procedure is important for studying earthquake propagation across large areas with no seismograph coverage. This earthquake analysis is the most admired result of his research by those who do not practice reflection seismology. For those who practice seismic reflection seismology, Curtis and his staff are now using scattered waves and ambient seismic noise to allow seismic interferometry to be better used for purposes of seismic reflection imaging. They have already used interferometry concepts to predict and remove ground roll from seismic data recorded for reflection purposes.

### Biography Citation for the Reginald Fessenden Award 2017 ^{[1]}

Andrew Curtis holds the chair of mathematical geoscience at the University of Edinburgh. Over the last 12 years, Andrew has published a succession of highly influential papers in the area of seismic interferometry and theoretical seismology, for which he is recognized through the Reginald Fessenden Award.

Andrew and I have maintained a strong collaboration since I first met him in 1997, shortly after we became research scientists at Schlumberger’s research center in Cambridge. I particularly recall a trip that Andrew and I made to Paris in 2002. It was inspired by recent findings in the field of time-reversed acoustics by Professors Mathias Fink and Roel Snieder. Andrew had organized a visit to meet Professor Albert Tarantola, who then accompanied us on visits to several of the labs in Paris working on these topics (including Fink’s lab). This trip was seminal for us both, as Andrew subsequently became one of the early key contributors in this evolving field of science, and it stimulated many of our research papers ever since. In a paper published in Physical Review Letters in 2005, Dirk-Jan van Manen, Andrew, and I formalized early interferometry results using Green’s theorem and showed that seismic interferometry provides the basis for efficient and highly accurate computation of Green’s functions in synthetic modeling applications. The impact of the method is not only to teach how large numbers of modeled Green’s functions can be effectively retrieved, but also changes the nature of modeling computations by converting them into massive crosscorrelation operations.

In another milestone in Andrew’s work on interferometry, he realized that sources of seismic energy such as active seismic sources or passive sources such as earthquakes could be used as virtual receivers. In a paper in Nature Geoscience in 2009, Andrew and coworkers showed that one earthquake could be converted into a virtual seismometer in the subsurface of the earth that would act as a dynamic strain sensor recording the wavefield from another earthquake. This provides recordings of seismic waves deep within the earth’s subsurface without the need to drill a well to install seismometers.

The advances in interferometry pioneered by Andrew’s research group also have had a direct impact on exploration seismics. In particular, the only existing commercial application of interferometry to surface seismics is the interferometric ground-roll prediction and removal method published in Geophysics in 2010 by Halliday et al. This work provided a completely new and model-independent means to predict and adaptively subtract scattered ground roll — a notoriously difficult problem in many areas where land seismic exploration takes place. This last example is particularly relevant because it involved Andrew and coworkers creating an entire theory of interferometry for scattered surface waves, deriving new results such as a generalized optical theorem for surface waves and expressions for surface-wave interferometry in attenuating media.

In 2010, Andrew and David Halliday published two more papers that combined this virtual-receiver interferometry with the more common virtual-source interferometry to construct the theory of source-receiver interferometry. This estimates Green’s functions between any pair of sources, receivers, or a source-receiver pair, and is directly related to seismic migration. Indeed, this method generalizes standard linear reverse time migration (RTM) to a nonlinear form of RTM that includes multiples, diffractions, refractions, and evanescent waves, which Andrew and Matteo Ravasi extended to image elastic (solid) media in 2013.

More recently, Andrew and his group have been among the pioneers of the extension of interferometry to Marchenko autofocusing redatuming and imaging theory, including publishing the first real-data example. Milestone achievements from Andrew’s group include the extension of Marchenko focusing from acoustic to elastic media, which shows how the elastodynamic Green’s function in the interior of a solid object can be obtained using only knowledge of the particle velocity and stress measurement at the surface together with a smooth background velocity model. Based on these developments, Andrew and coworkers have developed new approaches that use seismic data to construct primary reflections free from contamination by internal and free-surface multiples, thus obviating the need for multiple removals from seismic data.

Andrew is one of very few scientists in our community who generates truly novel ideas and potentially game-changing concepts in a wide range of fields. He is an exceptionally broad, productive, and multitalented scientist, who has demonstrated over the past decade how to develop and maintain a highly productive and diverse team of researchers in his academic research group. In 2015 alone, he published 14 papers on an impressively broad range of topics that include seismic migration, Monte-Carlo-based seismic tomography, wave scattering, and inverse theory, together with papers that are well beyond exploration seismology — on palaeontology (he codiscovered the oldest marine reefs built by animals, aged 548 Ma) and on psychology (the influence of individual experts on group decision making).

Andrew blends somewhat uniquely the fields of exploration geophysics, regional and global seismology, inverse theory, experimental design, pore fluid flow, expert elicitation, mathematical geology, and palaeontology. However, if I were to attempt to give Andrew one label it would be as a mathematical geophysicist whose contributions to the field of seismic interferometry have fundamentally changed the field of exploration geophysics, and seismology more generally.

## Biography 2005

**Andrew Curtis** received a B.Sc. (1990) in mathematics from the University of Edinburgh and a Ph.D. (1994) in geodynamics and seismology from Oxford University. For three years, he was a postdoctoral scientist in the Department of Theoretical Geophysics at Utrecht University in the Netherlands, where he worked on lithospheric and upper-mantle tomography. In 1997, Curtis joined Schlumberger Cambridge Research, where he worked on seismic wavefield decomposition, wavefield interferometry and time reversal, inverse theory, tomography and model-based survey design in linear and nonlinear systems, and geologic process modeling. In 2005, Curtis became the leader in exploration seismology at the University of Edinburgh, where he continues to explore his research interests.

## References

- ↑ (2017). ”Honors and Awards.” The Leading Edge, 36(10), 806–819. http://dx.doi.org/10.1190/tle36100806.1