Steven Constable

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Steven Constable
Latest company Scripps Institution of Oceanonagraphy
Membership Active
BSc Geology
PhD Geophysics
BSc university University of Western Australia
PhD university Australian National University

Steven Constable studied geology at the University of Western Australia, graduating with first class honors in 1979. In 1983 he received a PhD in Geophysics from the Australian National University for a thesis titled “Deep Resistivity Studies of the Australian Crust” and later that year took a postdoc position at the Scripps Institution of Oceanography, University of California - San Diego, where he is currently Professor of Geophysics. Steven is interested in all aspects of electrical conductivity, and has made contributions to inverse theory, electrical properties of rocks, mantle conductivity, magnetic satellite induction studies, global lightning, and instrumentation. However, his main focus is marine electromagnetism; he played a significant role in the commercialization of marine EM for hydrocarbon exploration, work that was recognized by the G.W. Hohmann Award in 2003, the 2007 SEG Distinguished Achievement Award, and now the SEG 2016 [[Reginald Fessenden Award. He also received the R&D 100 Award in 2010, the AGU Bullard Lecture in 2015, followed in 2016 by being named Fellow of the AGU. More recent efforts have involved the development of equipment to map gas hydrate and permafrost. Steven has served as an Associate Editor for the journal Geophysics, as a section secretary and corresponding editor for the American Geophysical Union, and on the MARELEC steering committee.

Honors and Awards

SEG Reginald Fessenden Award 2016

Steven Constable is one of three 2016 Reginald Fessenden Award winners [1]. His award is in recognition of "his development of marine controlled-source electromagnetic (CSEM) surveying technology." Strong endorsement letters recommending that Constable be recognized for this accomplishment have been written by several notable SEG people. His developments of sources and receivers for marine CSEM are impressive and important, as is his Occam inversion methodology for processing CSEM (and other) data. SEG awarded Scripps Institution of Oceanography (where Constable works) a Distinguished Achievement Award for CSEM in 2007, but this award honors the man behind the work at Scripps.

Biography Citation for the SEG Reginald Fessenden Medal 2016

By Sven Treitel

Steven Constable is widely known as one of the founding fathers of marine electromagnetic technology. At Scripps Institution of Oceanography at the University of California, San Diego, he collaborated with the late Chip Cox to develop the controlled source marine electromagnetic method (CSEM), which today is the most widely used marine EM technique in our industry. Steve was actively involved in the development of both the theory and the instrumentation of this approach. He foresaw the value of CSEM to the oil industry and convinced several of the majors to participate in this research. One of the most successful joint projects with industry resulted in his interaction with Len Srnka, then with Exxon Mobil. This turned out to be a fine example of the mutual benefits to be derived from a close collaboration between industry and academe.

Steve directs the Marine EM Lab at Scripps and also founded and continues to lead the Scripps Seafloor Electromagnetic Methods Consortium (SEMC), which is now in its 20th year and going strong. Until the recent downturn in the oil industry, CSEM had developed into a US$200 million per year exploration business — a success to which Steve has contributed through his vision and perseverance.

Steve studied geology at the University of Western Australia, from which he graduated with first-class honors in 1979. Four years later, he obtained a PhD in geophysics from Australian National University. Immediately thereafter, he moved to Scripps as a postdoc, and then progressed rapidly up the academic ranks to the full professorship he holds today.

Steve’s scientific interests are exceptionally broad, and range from the design of data-acquisition systems to the study of the electrical properties of rocks and to the conductivity in the earth’s mantle. He is the author and coauthor of some 90 publications; in exploration geophysics, he is perhaps best known for a stunningly successful paper published in 1987 titled “Occam’s inversion: A practical algorithm for generating smooth models from electromagnetic sounding data,” coauthored with Bob Parker and Catherine Constable, to whom Steve refers as the “smart” Professor Constable. In fact, she happens to be his wife of many years. They met as students and thus follow the illustrious footsteps of the late Sir Harold and Bertha Jeffreys. This paper has received more than 1000 citations, and is the second-most widely quoted paper in Geophysics. “Occam smoothing” has become a household concept in the geophysical inversion community, where it also enjoys widespread use among those doing seismic full-waveform inversion.

Yet another aspect of EM geophysics to which Steve and his students have made significant contributions is the provision of instrumentation, personnel, and expertise to the Japanese government in its efforts to explore for offshore gas hydrates. Steve’s group was involved with similar studies at various sites in the Gulf of Mexico, where a challenge is how to distinguish shallow gas features from gas hydrates. His group has developed a wide range of EM receivers for use along the seafloor as well as for towing in the water.

Worthy of mention is Steve’s and his students’ work with the acquisition, processing, and analysis of the first 3D CSEM/magnetotelluric survey over a known hydrocarbon deposit not conducted by industry. This data set, acquired over the offshore Australia Scarborough field, is being made available for public use by Scripps.

I have been privileged to know, and on more recent occasions, to interact with Steve in various ways. He understands a cardinal principle of scientific work, which is not to take oneself too seriously. He is an outstanding teacher and lecturer, and tries to get his points across simply, without cavalcades of equations galloping across the screen. Steve, now in midcareer, has many more years of science to look forward to and we, his colleagues, will continue to reap the benefits of his work.

Fall 2016 SEG/AAPG Distinguished Lecturer

Steven presented three lecture topics.

Geophysical Inversion: Which model do you want?

With a broad suite of geophysical inversion tools now available, it is seductively easy to submit your data, turn the crank, and obtain a model. But is the model meaningful? Are the data properly fit? How much does the model depend on the data, and how much on parameters in the inversion code, such as model discretization and regularization penalty? The inversion process depends as much, if not more, on the error structure of the data and inversion parameters as the data themselves. We all know that geophysical inversion is nonunique, but many people are surprised just how different models can be that fit the data equally well. And what exactly constitutes an adequate fit to the data? Without a rigorous analysis of error structure, choice of misfit can be highly subjective. Some rely on “Lcurves”, but it can be shown that they too are subjective, and depend very much on the choice of plotting parameters. Seeking to drive misfit down as low as possible can also be perilous – the least squares best fitting models for some problems are known to be pathological, and it is likely that this is true in general. In this lecture I shall attempt to provide an understanding of the practical issues associated with geophysical inversion, and provide a roadmap for avoiding common pitfalls.

Mapping gas hydrate using electromagnetic methods

Gas hydrate is found globally on the continental shelves and is important as an unconventional hydrocarbon source, a hazard to drilling and seafloor infrastructure, a potential source of potent greenhouse gas, and a confounding resistor in the interpretation of conventional marine EM data. Yet, estimates of global hydrate volume vary by three orders of magnitude and identified recoverable reserves are rare, the reason being that it is difficult to image hydrate using seismic methods alone. However, gas hydrate is highly resistive and presents a good EM target at high saturations. Conventional controlledsource EM (CSEM) methods can be used to image hydrate, but is inefficient because seafloor receivers need to be closely spaced to achieve the appropriate resolution in the upper hundreds of meters of the seafloor. Several groups, including Scripps Institution of Oceanography, have developed towed CSEM systems designed to map hydrate in deep water, and such equipment is now being used commercially to image hydrate with a potential for methane production. In this lecture I will describe marine gas hydrate, laboratory studies of its electrical properties, and the equipment that we use to image it, with case studies from offshore California and the Gulf of Mexico.

Marine EM: The past, the present, and the future

The high cost of deepwater exploration motivated the development of commercial marine magnetotelluric (MT) exploration in 1995, but it wasn’t until marine controlledsource electromagnetic (CSEM) methods burst upon the industry scene with the formation of three new contractors in 2002 that things got really exciting. Now the bubble has burst and the excitement has diminished, but marine EM remains an important tool for offshore exploration. Early mistakes were made as a result of poor instrumentation and a lack of good interpretation tools unlike seismics, EM relies heavily on inversion to produce useful results but both equipment and inversion codes have improved significantly. Still, EM images resistivity, not hydrocarbon content, and false positives occasionally occur, but false negatives are rare. That is, without an EM signature there is little chance of discovering economical hydrocarbons. In this lecture I will review the history, discuss the 10 important things you need to know about marine EM, and look to the future of the method.

SEG Distinguished Achievement Award, 2007

Professor Constable won the SEG Distinguished Achievement Award as a member of Scripps Institution in Oceanography for "significant contributions to the development of controlled-source electromagnetics for the direct indication of hydrocarbons and helping to build this technology into a commercially viable industry."[2]

Steven's blog about the lecture is available.[3]


  1. SEG Honors and Awards Ceremony, SEG Dallas 18 October 2016, Omni Dallas Hotel, Dallas Ballroom, International Exposition and Eighty-Sixth Annual Meeting, Dallas, Tx, p, 23.

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