2002 William Bowie Medal Winner
Adam Dziewonski was awarded the William Bowie Medal at the AGU Fall Meeting Honors Ceremony, which was held on 8 December 2002, in San Francisco, California. The medal recognizes outstanding contributions to fundamental geophysics and unselfish cooperation in research.
“The world is different because of Adam Dziewonski, the recipient of the American Geophysical Union’s highest honor, the William Bowie Medal. When I say different, I mean it literally. Open nearly any introductory geoscience textbook and look at the figures representing the structure of the Earth. Where there once was an onionskin Earth with radially symmetric layers, there now are color diagrams showing complex variations of seismic velocity that are representative of a dynamic and ever-changing Earth. Adam pioneered the technique of seismic tomography that has become ubiquitous in geophysics. Countless numbers of freshmen from Maine to Mexico are familiar with Dziewonski’s red and blue blobs painting an image of the mantle in motion. This accomplishment alone is worthy of recognition; in fact, Adam and Don Anderson received the Crafoord Prize from the Royal Swedish Academy of Science in 1998 for their work on Earth structure, but this is just the tip of the iceberg in terms of the accomplishments of an amazing man.
“Adam was born in Lwów, Poland. This part of Poland was acquired by the Soviet Union after World War II, but make no mistake, Adam is Polish! Adam received an M.S. from the University of Warsaw in 1960, and did his Ph.D. work at the Institute of Geophysics of the Polish Academy of Sciences. After graduation, Adam accepted a position as a research associate at the Southwest Center for Advanced Studies, in Dallas (which became the University of Texas at Dallas). Only one day after Adam arrived in Dallas (which apparently was nothing like Cracow), Adam met Freeman Gilbert at the annual meeting of the SEG. Thus began one of many fruitful collaborations with numerous seismologists. Adam and Freeman developed a technique for determining the source mechanism for earthquakes utilizing modal sums. Adam began routinely applying this methodology to all earthquakes above magnitude of 5.5 and developed the CMT (Centroid Moment Tensor) catalog. This catalog has become one of the most used seismological compendiums in history. Literally thousands of scientists have used the CMT catalog for studies on earthquake mechanisms, seismotectonics, and earthquake scaling laws. The CMT is now the standard way that seismologists learn about earthquakes, as descriptions of the mechanism location and other details are mailed to thousands worldwide within hours of an event occurring. Although the leadership of the project has now passed to one of Adam’s colleagues (and former student), Göran Ekström, it was Adam’s vision that made the CMT an essential part of the seismological research infrastructure.
“Adam enjoyed the company of Anton Hales at UT Dallas. Hales loves the every wiggle on a seismogram, and I believe that inspired Adam to work on improving the radially symmetric models for the Earth’s interior. Don Anderson and Adam published a detailed reference model called PREM (Preliminary Reference Earth Model). This led to work investigating deviations from this model, and eventually to seismic tomography. In a series of pioneering papers, Adam teamed with Hagar and O’Connell to use seismic structure as ‘geophysical input’ for geodynamics and mineral physics studies. Adam and his students and colleagues have continued to refine the structure of the Earth: superplumes beneath Africa, anisotropy in the inner core, the superswell in the Pacific–the list of studies is long.
“Although Adam’s scientific accomplishments are remarkable in their own right, they are equaled by his contribution to building the geophysical community through leadership. Adam was a principal architect of the Incorporated Research Institutions in Seismology (IRIS) and arguably is the ‘father’ of the modern Global Seismic Network (GSN), which is the primary tool in global seismology for the world today. In the late 1970s, the world networks were in grave disorder. Support for an aged WWSSN network disappeared, and various Department of Defense experiments in digital instrumentation had all but dried up and blown away. Adam, along with a few other senior seismologists, decided that only a network operated by an active academic community could be sustained in the long run. Adam doggedly pursued the development of a Global Seismic Network, which is composed of high-gain, broadband seismic stations that distributed data to all researchers. The GSN became one of the central facilities in IRIS and is now the primary source of seismic waveforms worldwide. Adam continues to be involved in IRIS and the GSN and has used his leadership position to promote free exchange of data.
“In summary, Adam Dziewonski is a remarkable geophysicist. He has shaped our understanding of the Earth and led the community to be truly cooperative. It is very hard to imagine a single seismologist who has not been affected by Adam and his contributions. The same can be said for most of the solid Earth geophysical community; he is a true giant in the field.”
—Terry C. Wallace, Jr., University of Arizona, Tucson
“Mr. President, ladies, and gentlemen: I am grateful for having my name added to the list of previous recipients of the Bowie Medal, many of whom are legends. I would like to thank all of my colleagues during the last four decades for making this occasion possible. In particular, I would like to thank Anton Hales for giving me his support, advice, and encouragement. His most important advice was to think of large-scale problems and not be afraid to question established paradigms and authorities. I am also thankful to Don Anderson and Freeman Gilbert for helping me get involved in the most challenging problems in global geophysics. The proof that the inner core is solid and the PREM Earth model came out of this cooperation. It is interesting that last year’s recipient of this medal, Dan McKenzie, also mentioned both of them as having had an important impact on his career; it is only fitting that both of them received this medal some years ago. During the last 20-25 years, I have been fortunate to have John Woodhouse and Göran Ekström as my coworkers and friends. With John, we have established mantle tomography as an indispensable tool for investigating of the Earth’s deep interior. With Göran, we have studied earthquakes and pursued more complex tomographic problems, such as mantle anisotropy; there are now CMT solutions for nearly 20,000 earthquakes. The discovery of strong radial anisotropy in the central Pacific shows that first-order effects in the Earth’s structure can still be found without escaping into the inner core. Thanks are also due students, postdoctoral fellows, and faculty colleagues with whom I worked at Harvard during more than 30 years.
“But all this might not have happened. At about the time that I was to be considered for tenure, one of the future recipients of this medal told the chairman of my department that there is not much left to do in seismology. This, and other issues, did not make things easy for a while. But then, on a long transit from Boston to Canberra in May 1974, I came to think that there must be enough information in Bulletins of the International Seismological Centre to resolve large-scale heterogeneity in the Earth’s mantle, if it exists. Upon my arrival, I mobilized Anton Hales to call the ISC director to send copies of magnetic tapes with all the data. I thought the work could be done in a couple of weeks, but I discovered that the tapes were nearly impossible to read. The data, in part, were written in free format; it was not expected that someone might want to extract this information ever again. It took about four months to obtain the first 3-D model of the mantle. Brad Hager, then a first-year graduate student, wrote, at the suggestion of Rick O’Connell, a term paper on the correlation of the geoid with the hypothetical gravity field predicted by the lower mantle velocity anomalies. The correlation was significant, even though the sign might have been wrong, and the rest, as they say, is history, even though it took another decade before most geophysicists were convinced that recovery of 3-D mantle structure is feasible.
“The start of my career coincided with the revolution that digital data and computers have brought to seismology. It was not always easy; manual digitization of some 150 daylong analog seismograms of the great Alaskan earthquake of 1964 took two years of very tedious work. But the gamble has paid off, as the density distribution in the Earth and the rigidity of the inner core became established. So did the digitization of the deep Colombian earthquake of 1970; in addition to further constraints on the structure of the Earth’s interior, the analysis led to the development of the modern way of studying earthquake mechanisms. Since 1975, I have been privileged to participate in a series of efforts to improve the global seismographic network. This turned out to be very successful, even though there are still battles to be won, particularly below the ocean bottom. Yet 35 years after the plate tectonic theory has become accepted, we still are not certain of the scale of mantle convection. It is becoming increasingly clear that seismology cannot by itself solve the problem of the Earth’s dynamics; neither can geochemistry, geodynamics, or mineral physics. We must learn to communicate at a level different from passing to each other what may represent a consensus in a given field. It is very important that we begin a multidisciplinary program of summer schools, workshops, and short and long courses at a level that cannot be afforded at any single institution; it is necessary successfully to bring Earth science into the ‘big science’ world, which it is now entering with the Earthscope program. I hope to be able to witness the beginning of implementation of such a program. “Thank you again.”
—Adam M. Dziewonski, Harvard University, Cambridge, Mass.