Nafi Toksöz

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Nafi Toksöz
M. Nafi Toksoz headshot.png
Membership Honorary Member
PhD university California Institute of Technology

M. Nafi Toksöz has made major contributions to the advancement of the science and profession of exploration geophysics throughout his 40 years as a professor at MIT. As the founder of MIT’s Earth Resources Laboratory, Toksöz’s impact is measured both in lives (the hundreds of students he has taught and mentored) and in scholarship (more than 180 technical publications and 3000 citations). The intellectual breadth of his scholarship is impressive: seismic exploration for hydrocarbons, full-wave sonic logging, rock physics, VSP, seismological applications for the Apollo program, electroseismic/seismoelectric, and earthquake seismology. Toksöz was recognized previously by SEG with Honorary Membership in 1999. The Seismological Society of America awarded him the Harry Fielding Reid Medal in 2006 for his outstanding contributions in seismology and earthquake engineering. Previous recipients of the Reid Medal include Sir Harold Jeffreys, Frank Press, Keiiti Aki, Freeman Gilbert, and other highly distinguished geophysicists.

Biography Citation for the Maurice Ewing Medal 2010 [1]

Contributed by Dan Burns and Arthur Cheng

The awarding of the Ewing Medal to Nafi Toksöz is profoundly fitting and deeply deserved. His scientific achievements, insight, and leadership in many areas of geophysics cover a period of almost 50 years; and his mentoring and advising of more than 100 graduate students, the majority of them serving as leaders in exploration geophysics, is a testament to his impact on our profession.

Early Years and Education

Nafi left his home in Turkey to study at the Colorado School of Mines where he received his BS in geophysics in 1958. He then went on to study under Frank Press at Caltech, where he received his MS (1960) and PhD (1963) in geophysics. He joined the MIT faculty in 1965 as an assistant professor in geophysics. This past year, after 44 years on the faculty, Nafi retired from MIT as the Cecil and Ida Green Professor in Earth and Atmospheric Sciences. Nafi has received scientific achievement awards from NASA, Colorado School of Mines, and the Los Alamos National Laboratory. He is a fellow in the AGU, an Honorary Member of SEG, and winner of the Harry Fielding Reid Medal from the Seismological Society Honors and Awards citations of America. He has published hundreds of papers and edited books such as Seismic Wave Attenuation, Vertical Seismic Profiling, and Strong Ground Motion Seismology. He has served on review boards and visiting committees for academic departments, national laboratories, governments, and industry.

Professional Career

Throughout his career Nafi has also proven himself to be a consistent leader in identifying the new and important research areas in geophysics. Nafi’s first love, and the foundation of his scientific legacy, is seismology. Nafi’s work in seismology has its roots in earthquake seismology and understanding the structure of the Earth’s interior. From those beginnings, he expanded his inquiry to the Moon and planetary interiors. His work on the Apollo program included placing the seismometers on the Moon. His quest to interpret velocity and attenuation measurements led to the development of models of wave propagation in heterogeneous media, including the Kuster-Toksöz model and its application to explaining the effect of pore shape and fluids on seismic velocity, attenuation, and pressure dependence. In the late 1970s and early 1980s, Nafi and his students helped define the field of borehole acoustic logging, developing theory, models, and data analysis methods to estimate rock properties from acoustic logs: velocity dispersion, permeability estimation, and fracture characterization. In 1982 Nafi founded the Earth Resources Laboratory at MIT. ERL continues to be one of the preeminent applied geophysics labs in the world thanks to Nafi’s extraordinary insight and energy. Nafi served as director of ERL for 15 years, and during those years helped ERL to develop leadership in many research areas of importance, including acoustic logging, VSP, crosswell seismology, applications of seismic scattering, rock physics, electroseismics, and massively parallel computing. Though retired, Nafi continues to be an active member of ERL and a leader in passive seismic reservoir monitoring applications.

Even greater than his scientific achievements is Nafi’s work as a supportive advisor to more than 100 graduate students and research associates. In addition to his scientific guidance, Nafi has always taken a keen interest in nurturing the careers of his students and being a constant and supportive mentor throughout their lives and careers. His graduates hold key positions in industry and academia throughout the world. Through his students, Nafi’s support of the profession of exploration geophysics continues to reach through several generations and touches our industry in every continent of the world.

The awarding of the Ewing Medal to Nafi Toksöz is both a wonderful recognition of his achievements and a well-earned tribute to all he has given to our profession.

SEG Honorary Membership 1999 [2]

SEG is honoring Nafi Toksöz with Honorary Membership for his major contributions as a scientist and educator in the fields of rock physics, borehole geophysics, wave propagation, and computing. Nafi is the author or coauthor of more than 400 papers that have had a significant impact on the petroleum industry, and he supervised the theses of more than 100 students who subsequently embarked upon geophysics careers in industry and academia. In 1982, he founded MIT’s Earth Resources Laboratory, which he directed until he retired in 1998.

Biography Citation for SEG Honorary Membership

Contributed by Arthur Cheng, Neal Goins, and David Johnston

Nafi Toksöz’s contributions to geophysics are extensive. As a professor and director of Earth Resources Laboratory at the Massachusetts Institute of Technology, his impact has ranged from rock physics to massively parallel computing.

Nafi, a native of Turkey, received a bachelor’s in geophysics (1958) from the Colorado School of Mines, and a master’s (1960) and doctorate (1963) in geophysics from the California Institute of Technology. Nafi joined MIT in 1965 and became a full professor in 1971. He designed and became director of MIT’s Wallace Geophysical Observatory in 1975, a position he retains. Nafi founded the Earth Resources Laboratory in 1982 and directed it until 1998. ERL’s faculty, staff, students, and visiting scientists perform research that will further understanding of the earth, its resources, and the environment.

ERL focuses on subsurface imaging and characterization, particularly fluid movement in petroleum and geothermal reservoirs.

Nafi’s achievements include authorship or coauthorship of more than 400 papers. Those significantly impacting our industry include:

• Rock physics. Laboratory measurements and theoretical studies of seismic velocity and attenuation have furthered understanding of wave propagation in rock. The Kuster-Toksöz (1974) effective medium theory remains an important tool for predicting variations in seismic velocities—especially in fractured rocks and carbonates.

• Borehole geophysics. Nafi and students have extended the use of full waveform acoustic and dipole sonic logs. Applications include estimation of permeability using Stoneley waves and shear-wave anisotropy using crossdipole logs.

• Wave propagation. Modeling code has been developed for full 3-D elastic wave propagation, facilitating research in borehole and surface seismic. ERL’s state-of-the-art modeling algorithms yield better interpretation of the diverse seismic data acquired today. A recent example is the study of the conversion between seismic and electrical energy through flow in porous media.

• Computing. ERL pioneered the use of massively parallel computing for seismic processing and modeling. Their 512-node nCUBE2 system is one of the largest in a research group.

Nafi also has an uncanny ability to foresee the next areas of enquiry in geophysics, and the instinct, perspective, and depth of knowledge to guide his efforts along the critical paths. Nafi and students have significant accomplishments in earthquake seismology, nuclear test ban monitoring, plate tectonics, and planetary science. He has edited books on Seismic Wave Attenuation and Vertical Seismic Profiling: Advanced Concepts(both for SEG) and Strong Ground Motion Seismology.

However, Nafi’s greatest contribution may be the people he has nurtured. We had the privilege of studying together under Nafi. No matter how busy, he has time for whoever needs guidance—the newest undergraduate or seasoned postdoc. No matter what the subject—personal, technical, or career—he can identify the key issues, sketch the way forward, and deliver an encouraging pat on the back. Once under Nafi’s wing, you are there forever—no matter how senior you are in your career, a meeting with Nafi always includes valuable advice and priceless encouragement. The results? Over 100 theses have been completed under Nafi’s tutelage. His students occupy senior positions at ARCO, Baker Hughes, Chevron, Elf, Exxon, Halliburton, Mobil, Schlumberger, and Shell. Those who have entered academia have gone on to UCLA, The University of Calgary, MIT, Texas A&M, Stanford, Harvard, Columbia, and the University of Oklahoma.

Nafi has a special interest in education and training of the international geophysical community including students from China, Nigeria, Holland, the Middle East, and his native Turkey. Nafi Toksöz’s technical contributions speak for themselves. His guidance of students and colleagues, including many of you reading this citation, speak through their work and careers. He truly deserves SEG Honorary Membership.

Honorable Mention (Geophysics) 1997

Oleg V. Mikhailov, Matthijs W. Haartsen, and M. Nafi Toksöz received 1997 Honorable Mention (Geophysics) for their paper Electroseismic investigation of the shallow subsurface: Field measurements and numerical modeling.[3]


  1. 2010 SEG Annual Meeting, SEG Honors and Award Program
  2. 1999 SEG Annual Meeting, SEG Honors and Awards Program
  3. Mikhailov, O. V., M. W. Haartsen, and M. N.Toksöz (1997)Electroseismic investigation of the shallow subsurface: Field measurements and numerical modeling, GEOPHYSICS 62(1):97.