Evert Slob
The 2023 Frank Frischknecht Leadership Award
It is with great enthusiasm that we nominate Prof. Dr. ir. Evert Slob for the 2023 Frank Frischknecht Leadership Award. Evert has made outstanding contributions to various fields of applied geophysics throughout his career, in particular in ground penetrating radar and in electromagnetic methods in general. He has supervised a large number of B.Sc., M.Sc., and Ph.D. students, postdocs, and visiting scholars and has always put the interest of science and the professional development of the individuals ahead of his own interest. Within his career in the last 30+ years, he has authored and co-authored over 160 peer-reviewed articles with his co-authors and students, co-authored a book, and supervised many Ph.D. theses. In the following, we highlight five of Evert’s major achievements and demonstration of leadership.
Passion for Teaching and Mentoring
The mentoring and leadership shown by Evert has had a great impact on all of his former students and postdocs who are signing this nomination letter. We have all profited from his great trust in the abilities of students and coworkers and his gift for empowering his collaborators, rather than taking the limelight for himself. As such, Evert can be credited with having formed many more scholars than the few signing this letter, scholars who advance the field of near-surface geophysics now and will do so in the future. A prime example of this is that Evert has been one of the main driving forces behind the Joint Master in Applied Geophysics, an international M.Sc. programme offered jointly by TU Delft, ETH Zürich, and RWTH Aachen, starting in 2006 (within the IDEA-League network). Within its 16+ years of existence, it has become a globally recognized M.Sc. programme by both academia and industry. His educational skills were recognized by the Board of TU Delft with the appointment as Director of Education for Civil Engineering and Geosciences from 2014 until 2018.
Leadership in the Near-Surface Community
Evert is the initiator of the biennial International Workshop on Advanced Ground-Penetrating Radar (IWAGPR), with its inauguration in 2001 in Delft. The following two workshops also took place in Delft (2003 organized by O. Yarovyi, 2005 by S. Lambot and A. Gorriti), after which it was hosted by different cities in Europe. He organized the IWAGPR again in 2019, together with EAGE, where he was also co-chair of the local advisory committee (with R. Ghose) for the 2019 EAGE Near-Surface Geoscience Conference and Exhibition. He was a member of the International Advisory Committee for every GPR conference and has been on all Technical Committees for the IWAGPR. The well recognized workshop series continues, with its most recent edition, the 11th, taking place in Malta in 2021. He further co-organized the 10th edition of the biennial International Conference on Ground-Penetrating Radar in 2004 in Delft.
Ground-Penetrating Radar (GPR)
Besides the workshop and conference activities above, Evert contributed, in collaboration with Sébastien Lambot, to the development of a novel method to model far-field GPR data, especially through his deep knowledge of Green’s functions. This method uses an intrinsic antenna representation through global reflection and transmission coefficients, together with exact Green’s functions for wave propagation in planar layered media (Lambot et al., 2004). This new approach resulted in unprecedented accuracy and computational efficiency for radar modelling. It permits the retrieval of electromagnetic soil and material properties through full-waveform inversion. Sébastien came to TU Delft in 2004 and 2005 as a postdoc to work on and further develop the method with Evert (EU Marie-Curie fellowships). They applied the new methodology for the determination of hydrogeophysical properties of the shallow subsurface and integrated the electromagnetic model with a soil hydrodynamic model. This very fruitful collaboration continues to the present, with Sébastien being now a Professor at UCLouvain.
Electric Soil Properties
With several Ph.D. students Evert worked on macroscopic models for soil and rocks using electric and seismo-electric responses (Ainhoa Gorriti, Jan Willem Plug, Menne Schakel, Michel Ponziani, Mohsen Kavian, Christiaan Schoemaker, Claudio Patriarca and Niels Grobbe). These works included the entire process from theoretical development to laboratory measurements and field tests, and were applied to GPR, diffusive electromagnetic, and seismo-electromagnetic measurements.
They successfully showed, for instance, that the measured seismo-electromagnetic response from porous samples is in agreement with the developed theory. Moreover, they proved that the magnitude of the acoustic-to-EM conversion is a function of the salinity, which is an important tool for near-surface characterisations. Other material characterizations included heritage buildings and roads (e.g., Patriarca et al., 2013).
Controlled Source Electromagnetic Method (CSEM)
Evert not only derived analytical solutions for full- and halfspace solutions of the electromagnetic field (e.g., Slob et al., 2010), but also the Green’s functions for the electromagnetic field in planar layered media for the full wavefield in the wavenumber-frequency domain (Ziolkowski and Slob, 2019). This neat derivation of the electromagnetic fields complements the previous approaches using potentials, and it led to open-source computer codes that are widely used by the community today (Hunziker et al., 2015; Werthm¨uller, 2017).
In addition to the above-mentioned achievements, Evert contributed with his pioneering and rigorous research also to other geophysical topics of high interest, such as interferometry and Marchenko imaging. We note that Evert also served as the Editor-in-Chief of Geophysics from 2013 until 2015, and as a Member of the Board of Directors of SEG. Prof. Evert Slob is not only an outstanding researcher, educator, and colleague, but also an ideal leader of electromagnetics in Near-Surface Geophysics and a particularly pleasant person to work with, with exceptional human qualities. We warmly propose Prof. Evert Slob for the 2023 Frank Frischknecht Award.
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| PhD university | TU Delft |
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Evert Slob has contributed key scientific and technological advances in electromagnetic interferometry in a series of papers from 2007 to 2013. He is a contributor to the development of Marchenko imaging.
The 2020 SEG Reginald Fessenden Award [1]
by Roel Snieder, Kees Wapenaar, and Sven Treitel
Evert Slob has contributed key scientific and technological advances in electromagnetic interferometry in a series of papers from 2007 to 2013, although these papers represent only a small selection of his 120-plus publications. What is clear from this body of work is the power of Slob’s basic theoretical understanding and his ability to create entirely novel areas of theory and methodology that were previously beyond the reach of most in academia or industry. Evert Slob also devotes a significant portion of his scientific endeavors to support, engage, and mentor students and postdoctoral scientists.
Biography Citation for the 2020 SEG Reginald Fessenden Award
Evert Slob is an eclectic researcher who has published 128 research papers in leading journals, including Geophysics. His book Introduction to Controlled-Source Electromagnetic Methods, coauthored with Anton Ziolkowski, is published by Cambridge University Press. Evert’s research is extremely broad and includes important contributions to the field of seismic interferometry. In this field of research, one reconstructs the waves that propagate between two receivers by cross- correlating the signals generated by sources located on a surface that surrounds these receivers. Evert showed that when the sources are placed on a surface between the receivers, one can extract the waves propagating between these receivers by convolving the waves recorded on these receivers. Evert has been instrumental in extending the concepts of seismic interferometry to electromagnetic fields, and he has been among the early researchers to point out that the field of seismic interferometry has its roots in early work on fluctuations in electrical systems.
A limitation of seismic interferometry in its earliest formulations was that the concept was formulated for systems that conserve energy, which precluded geophysical applications to electromagnetic fields where the electrical conductivity leads to a loss of field energy. This limitation can be overcome largely by using multidimensional deconvolution that Evert developed with coworkers from Delft University of Technology. This method not only helps overcome limitations imposed by the dissipative nature of electric fields and seismic waves, it also is a powerful tool to utilize Marchenko imaging for seismic waves. Multidimensional deconvolution also helps strip away the imprint of the overburden in controlled source electromagnetics (CSEM). Evert also showed that synthetic aperture methods can be applied to CSEM fields, which makes it possible to steer these diffusive fields, a technique that was deemed to be impossible.
Evert has also been a great contributor in the area of Marchenko imaging. With his colleagues at Delft, Everthasbeenactiveinpushingthisnewfieldofresearch forward. One of his contributions in Marchenko imaging is, once more, related to dealing with dissipation, which he published in Physical Review Letters, a leading physics journal. This development is not only important for seismic applications; it also opens an avenue to apply Marchenko imaging to electromagnetic fields. The principle and implementation of Marchenko imaging has been difficult to communicate to the geophysics community because of its difference from traditional imaging methods. Evert’s 2014 paper in Geophysics is one of the clearest papers on Marchenko imaging.
Evert’s contributions go beyond his research. He has a mindset of service and has exemplified this mindset in many different ways. He was associate editor of Geophysics from 2009 to 2013 and editor in chief from 2013 to 2015. Within the Delft University of Technology, Evert was director of education for Civil Engineering and Geosciences from 2014 to 2018. He serves as chair of the Career Development Committee at Delft. Evert served on the executive board of the IDEA-league MS program. In this program, a cohort of MS students travels between a number of European universities taking classes and doing research. Because a number of institutions are involved, this program requires an intense coordination effort. Evert makes an incessant and empowering contribution to the growth of young researchers. He does this by providing them with research guidance and advice, but his contribution goes much further. Evert is a true “people magnet.” He not only guides students in their research; he also acts as a mentor for students — even those who don’t work with him. Most impressive about Evert is his ability to combine his research talents and warm interpersonal skills with a modesty that belies his achievements.
Biography 2013[2]
Evert Slob received an M.Sc. (1989) in mining and petroleum engineering, and a doctorate (1994) in applied sciences from Delft University of Technology (TU Delft). In 1995, he joined the Department of Applied Earth Sciences, TU Delft, where he is a professor of geophysical electromagnetic methods and director of studies of Applied Earth Sciences in the Department of Geoscience & Engineering. He was the 2012-2013 assistant editor for GEOPHYSICS and associate editor for Near Surface Geophysics. His current research interests include EM interferometry, advanced imaging and inversion techniques, hydrogeophysics, heterogeneity determination, and soil characterization including the study of fundamental relations between geologic and EM and electrokinetic properties. He has published 95 international peer-reviewed journal papers on these subjects. He was the general chair of the 10th International Conference on GPR in 2004. He organized more than a dozen international workshops and conference sessions and was guest editor for 11 special journal issues on GPR and hydrogeophysics.