Citation

Professor Mark Harrison of the University of California, Los Angeles, is a geochemist and geochronologist whose interests and contributions span a broad range, including, but not limited to, present-day tectonics of the Himalayas and Tibet, the nature of the Hadean Earth and theoretical and applied thermochronology. 

Early in his career, Mark led the advancement of the argon-40/argon-39 isotopic system to a new level of sophistication that made it possible to recover quantitative information on the time-temperature histories of strategically chosen crustal rocks. He and his colleagues and students applied this system to some of the most perplexing and important tectonic settings of the day, including relatively unstudied regions such as the Tibetan Plateau as well as long-debated terranes such as the northern Appalachians. Mark’s contributions to potassium-feldspar thermochronology through the multi-diffusion domain (MDD) model — developed with Oscar Lovera and Frank Richter — were particularly far reaching. Their impact was perhaps greatest in Tibetan tectonics, where Mark and his team documented the Gangdese thrust, a south-directed fault carrying the rocks of southern Tibet over the Tethyan sequences to the south. With structural geologist An Yin, Mark demonstrated that the Gangdese thrust system (GTS) spanned the entire length of the suture between the syntaxes, making the GTS the oldest collision zone-wide thrust system responsible for the earliest episode of uplift in southern Tibet. Mark and colleagues also showed that “continental extrusion” played an important role in accommodating convergence and that the large “lithospheric faults” of Asia can move at San Andreas-like speeds. 

Harrison’s second “grand contribution” to crustal geoscience was his “mission to really early Earth.” In the early 2000s, he organized an international consortium to investigate the Hadean (4+ billion years old) zircons of Western Australia’s Jack Hills, enlisting researchers from Europe, Australia and North America. The effort led to vastly expanded databases of Hadean zircon ages and oxygen and hafnium isotope ratios, as well as detection of fission xenon and an estimate of the uranium/plutonium ratio of early Earth. Taken together, the results argue strongly for the existence of continents as early as 4.4 billion years ago and crustal cycling like that of today. Mark later turned his attention to mineral inclusions in the Jack Hills zircon suite, which ultimately led him to suggest that plate tectonics was well underway in the Hadean and that life had emerged by ~4.1 billion years ago. These suggestions have stimulated the imaginations and energy of early-Earth researchers worldwide.

Response

Thank you, Bruce, for the generous citation and my AGU colleagues for the award of the Walter H. Bucher Medal. I learned on AGU’s website that the medal was established in 1966, the year following Professor Bucher’s passing. I was surprised for a couple of reasons to see James Gilluly listed as its first recipient and wondered what Walter would have thought. While both men focused on lithospheric evolution and were giants in that field, they held profoundly opposing tectonic views. Bucher thought that orogeny was due to mantle volume changes that caused synchronous, global pulsations of the overlying crust, whereas Gilluly, no doubt influenced by tremors he’d felt in his University of California, Los Angeles, lab, believed that orogeny was globally continuous. But he also championed the view that granites were largely amagmatic, instead forming from metasomatizing fluids introduced into the crust. Both men had advanced original concepts that were consistent with the equivocal evidence of the time but profoundly wrong from our current, global tectonic perspective. In this I’m reminded of Kevin Burke’s aphorism that one’s distinction in science is often measured by how many years you set your field back. What I hope Kevin meant is that being creative and being right can be two different things but both should be appreciated because without the fuel of new ideas — even the ones that momentarily run us up blind alleys — our field would languish. As I peruse the list of Bucher medalists over just the last generation, I’m heartened to see proponents of diametrically opposing views of, for example, continental growth history and the origin of inverted metamorphism. What does this mean? Fifty years on, despite how much more we know about how our planet works than in the Bucher-Gilluly era, we continue to debate fundamental issues of deep time just as they did. For those of you just starting your careers, this is good news. Simply put, those that came before you failed to resolve the most intractable, and thus arguably most interesting, problems in continental geodynamics. This is our unintentional gift to you. Enjoy the journey as you anticipate the AGU medalists of 2050; I hope you’ll have as much fun as I’ve had. 

— Mark Harrison 

University of California, Los Angeles

Los Angeles, California

Citation

For novel interpretations of crustal and lithospheric evolution that have advanced our understanding of subduction and orogenic processes.

Field Photos

Video

Philip England was awarded the 2018 Walter H. Bucher Medal at the AGU Fall Meeting Honors Ceremony, held on 12 December 2018 in Washington, D. C. The medal is for “original contributions to the basic knowledge of the crust and lithosphere.”

Citation

Philip England recognizes that the goal of science is to understand nature’s processes, the essence of understanding is the ability to predict from general conditions, bringing understanding to Joe Sixpack requires simplicity, and simple understanding can be expressed most clearly by algebraic expressions, or scaling laws. With Steve Richardson and later with Margaret Moore (and Carslaw and Jaeger), he showed how erosion affects crustal temperatures. With Alan Thompson, he showed how the thermal history of buried rock, and therefore metamorphism, depends on rates and depths of burial and exhumation. With Tim Holland (and Archimedes), he revealed the conditions required for ultrahigh-pressure rock to return to the surface in the face of subduction shear. With Greg Houseman, Dan McKenzie, and Leslie Sonder, he combined the two major forces that limit elevations of deforming lithosphere—friction or viscosity and gravity—into one dimensionless number, the Argand number. With this simplification, he then explained many aspects of the large-scale distribution of active deformation, like present-day velocities and strain rates, rotations about vertical axes, crustal thicknesses, and subcrustal seismic anisotropy. With Stephen Bourne and Barry Parsons, he showed how slip rates on faults can scale simply with the spacing between faults. With Richard Katz and Catherine Wilkins, he showed how the positions of volcanoes at subduction zones depend simply on the subduction rate and the dip of the downgoing slab. In a counterintuitive, homely analogy, the faster you thrust ice beneath your bed, the warmer you will be (provided that the movement of your ice forces a circulation of warm water above it)! Not just a theorist who has reduced nonlinear differential equations to algebraic scaling laws, he has also led efforts to obtain new data, especially GPS measurements. Finally, as a public servant, he organized a multidisciplinary program, Earthquakes Without Frontiers, to study both the science and the societal impacts of earthquakes in continental regions, where they have taken their greatest toll but are least well understood.

Philip England has brought simple understanding to a wide variety of thermal and mechanical processes in the solid Earth. Young scientists could benefit from examining how he chooses, then poses, and finally solves problems.

—Peter Molnar, Department of Geological Sciences, Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder

Response

Thank you, Peter. Your nomination and the support of friends who must have written unreasonably kind letters embody what I value most. Receiving the Bucher Medal evokes many memories of interactions with the dynamic and inclusive community that is AGU.

Nothing of worth that I have done would have been possible without Pam; doing justice to her support would require volumes, which she would not want me to write. Our children provide a counterpoint: By their unremitting ridicule and disrespect, they inspire me constantly to question the value of what I do.

I have been extraordinarily fortunate in the people who influenced me. I cannot imagine a better introduction to research in the Earth sciences than Stephen Richardson and Ron Oxburgh provided. They had inexhaustible curiosity about the Earth, and encouraged their students to employ whatever tools were available to solve problems of interest. Few who know Dan McKenzie would dispute that an exchange of views with him is one of the most bracing experiences our discipline has to offer; 4 years of Dan’s stimulation and generosity were an outstanding experience.

Decades ago, when you and I first grouched together, the search for simplicity in geology seemed natural. The facility with which computer models now spin seductive webs of “realistic” images has made that view unfashionable. I nevertheless remain convinced that nature does leave clues lying around that reveal her working through their simplicity. It has been immense fun to pursue those clues with friends much smarter than I, particularly you, Greg Houseman, and Rich Katz. I’ve had equal fun, with added scenery, in the company of Haris Billiris, James Jackson, Demitris Paradissis, Barry Parsons, and George Veis (whose understanding of satellite geodesy predates satellites themselves). It has been stimulating and sobering to work with James, and new friends in other disciplines, on the far from simple challenges of seismic risk across Eurasia. Lack of space prevents mention of many others; I hope you know who you are.

For what it’s worth, my advice to young scientists is embedded above. Choose a nascent field and seek the best mentors; I was fortunate, but your choice now is even richer. Lastly, for the not-so-young: Pressures from has-been counters, from those who mindlessly equate universities with businesses, and from bigots of all shades imperil the openness, inclusivity, and liberality that are essential to the flourishing of young minds. Resist.

—Philip England, University of Oxford, U.K.

Samuel A. Bowring was awarded the 2016 Walter H. Bucher Medal at the AGU Fall Meeting Honors Ceremony, held on 14 December 2016 in San Francisco, Calif. The medal is for “original contributions to the basic knowledge of crust and lithosphere.”

Citation

Sam Bowring’s expertise as a field geologist, his enormous breadth of knowledge, and his unwavering pursuit of the highest possible precision and accuracy in ­­­uranium-­­­lead geochronology has transformed our understanding of the time when life began, the timing and triggers of the great mass extinctions, and the manner in which the Earth’s earliest crust evolved.

Sam determined the duration and rate of biological evolution at the ­­­Pre-­­­Cambrian/­Cambrian boundary—the ­­so-­called explosion of life that is the single most important evolutionary event in Earth history. Sam dated key volcanic strata within the sedimentary layers that record the Early Cambrian evolution of life and showed that the Cambrian period began 541 million years ago and that the Early Cambrian interval spanning the explosion of life lasted only 5 million to 6 million years. Sam showed that during this brief time interval more phyla than have ever since existed on Earth came into existence. This represents a truly profound and astonishing new discovery about how life evolved on Earth.

Sam has also established the timing and duration of the most significant biological extinction event in Earth history—the one defining the end of the Permian. Sam and colleagues have demonstrated that the extinction occurred in a time interval of less than 60,000 years and that the surge in light carbon predates the extinction by only 10,000 years. Having now established the precise timing of the extinction event and the global environmental crisis that preceded it, Sam has provided fundamental constraints on the forces that led to the environmental crisis resulting in the greatest extinction in Earth’s history.

Sam’s work on the world’s oldest rocks, the Acasta gneisses, has led to a new understanding of the processes leading to the early growth of continental crust. Through his rigorous field efforts in the Northwest Territories of Canada and his geochronological studies, Sam established that the Acasta gneisses were Priscoan in age (>4 billion years old). His geochemical studies of these early crustal remnants showed that these rocks were similar to today’s ­­­arc-­­­derived continental crustal rocks, supporting the notion that crustal recycling started early on in Earth history and has continued to the present.

—Tim Grove, Massachusetts Institute of Technology, Cambridge

Bryan L. Isacks was awarded the 2014 Walther H. Bucher Medal at the AGU Fall Meeting Honors Ceremony, held on 17 December 2014 in San Francisco, Calif. The medal is for “original contributions to the basic knowledge of the crust and lithosphere.”

Citation

Many would agree that the recognition of plate tectonics has been the most significant development in the geosciences since Darwin and Wallace proposed evolution by natural selection. Reduced to its essence, plate tectonics includes seafloor spreading, transform faulting, subduction of oceanic lithosphere, and rigid-body motion of lithospheric plates. No one has made a greater contribution to our understanding of the subduction of oceanic lithosphere than Bryan Isacks.

With Jack Oliver, Isacks reintroduced the concept of the lithosphere and showed how its subduction explained a plethora of peculiarities of island arc structures. Isacks, Oliver, and Lynn Sykes wrote definitive papers showing how many key aspects of plate tectonics are defined by earthquake seismology. In these papers Bryan demonstrated that fault plane solutions of intermediate and deep-focus earthquakes require that those earthquakes occur within the downgoing slab of lithosphere, and he used those solutions to place constraints on the forces that drive plate motion. With Muawia Barazangi and others, he showed that the deep structure of back-arc basins implied seafloor spreading there.

Like most major contributors to plate tectonics, Bryan moved away from it in the 1970s, and he turned to subduction beneath a continental margin, the Andes, where the idealized rules of plate tectonics fail. With Barazangi and in a later elaboration with Teresa Jordan and others, he pointed out the geologic similarity between portions of the Andes where subduction occurs at a gentle angle and what geologists had inferred for the tectonic development of the western United States from 80 to 50 million years ago. His leadership in this area of research made Cornell a major center of Andean research.

Then 25 years ago, Isacks was one of the first to exploit digital topography to understand both geodynamics and erosion. He combined the fact that glaciers form at high altitudes with the widely accepted notion that glaciers erode more rapidly than rivers, and he coined the term “glacial buzz saw” to explain the hypsometry with seemingly flat high terrain despite many deep glacial valleys.

An unusually humble man, Isacks has received only one important accolade, the respect and appreciation of many students; ~35 of the ~45 graduate students whom he had advised attended a celebration of his 70th birthday. Until now, Bryan Isacks may have been AGU’s most outstanding scientist who had never received a medal or formal recognition of his contributions. We are delighted that this oversight has now been set right.

—Peter Molnar, University of Colorado Boulder, Boulder, Colo.

—Frank Richter, University of Chicago, Chicago, Ill.

Response

I thank Peter Molnar and Frank Richter for their very kind and generous citation.

In the 1960s I was lucky to have been immersed in the exciting and enabling culture of collaborative research at Lamont when the ideas of plate tectonics emerged, seemingly, by a process of “self-organized criticality” involving the interactions of numerous scientists in England, Canada, and the United States. In that network of interactions at Lamont I particularly linked with my thesis advisor Jack Oliver and colleagues Lynn Sykes, Peter Molnar, Muawia Barazangi, and Walter Mitronovas.

In the 1970s, after moving to Cornell, Muawia Barazangi and I came upon the segments of alternating steep and flat dipping plates that are subducting beneath the Andes. We were taken by the remarkable correlation between plate dip and Andean volcanism and topography. In the early 1980s, Rick Allmendinger and Terry Jordan came to Cornell with ideas about the role of flat subduction in the Laramide tectonics of the western United States. We were amazed at the analogy between the Laramide western United States and the late Cenozoic tectonics of the central Andes. Sharing this amazement were Suzanne and Bob Kay, who were working on ­subduction-­related volcanism in the Aleutians, and Art Bloom, who was involved in NASA’s Landsat and Shuttle Imaging Radar programs. The six of us started the Cornell Andes Project in the early 1980s, and it continues to this day.

The close relationship between the dip of the subducted plate and upper plate tectonics led me to the outstanding signal of Andean tectonics, the Central Andean Plateau. As revealed by digital topography, a picture emerged involving plateau uplift by lower crustal shortening, a crustal-scale monocline defining the seaward edges of both the plateau and the volcanogenic asthenospheric wedge, and the enhanced bending of the Bolivian Orocline. In NASA’s Earth Observing System (EOS) and spaceborne imaging radar-C (SIR-C) programs I worked on satellite remote sensing of glaciers past and present and the coupling between mountain building and climate. I was fortunate to have very talented and enthusiastic graduate students, who worked as colleagues and often led the way, as in the old days at Lamont. They deserve a significant piece of the medal.

Recently, I’ve used digital topography to show how ice sheets have so beautifully sculpted the Finger Lakes’ landscape. The resulting video is narrated by my wife, Marjorie Olds, who, as my life coach, also owns a piece of the Walter Bucher Medal.

—Bryan L. Isacks, Cornell University, Ithaca, N. Y.

James R. Rice was awarded the 2012 Walter H. Bucher Medal at the AGU Fall Meeting Honors Ceremony, held on 5 December 2012 in San Francisco, Calif. The medal is for “original contributions to the basic knowledge of the crust and lithosphere.”

Citation

Jim Rice’s long and distinguished record of seminal theoretical contributions to our understanding of fault and earthquake mechanics is unprecedented. His work has influenced the entire community working on earthquake science. It is hard to imagine how any single individual in the future could ever come close to making so many fundamental advances in this field. He focuses on the most important problems and advances our understanding of them and their solutions by insightful analysis using many mathematical and numerical techniques, supported by his encyclopedic knowledge and understanding of all relevant theoretical, experimental, and observational information. His contributions to geophysics include not only his own personal research, but the influence he has had on many exceptional students, postdocs, and collaborators who are leaders in the field. There are so many of these that I will mention none, for lack of space and lest I leave important ones out!

Jim started in engineering and began working on earthquake problems while at Brown. After moving to Harvard he gradually shifted nearly all of his research to geophysics. His more than105 strictly geophysical publications are less than half of his total publication list, which has more than250 entries! His engineering mechanics papers are extremely influential in that field and many of them also indirectly influence the geophysics literature. Throughout his career Jim’s papers have defined the cutting edge of research. I can only allude to a few of his contributions here.

Jim’s first work in geophysics involved the interrelationship between pore fluid pressure, dilatancy, and strength of saturated rocks. These topics frequently have been the theme of his papers ever since. The contexts include the absolute and relative weakness of the San Andreas Fault, the influence dilatancy has on fault stability, and the role possibly played by thermal pressurization of pore fluid on earthquake nucleation and during dynamic earthquake rupture.

Another set of Jim’s influential contributions are his many papers on rock friction, both rate and state friction and high-velocity friction, and their use in earthquake simulations. These include the behavior during a sequence of earthquake cycles and what can occur during a single dynamic rupture, for example whether ruptures propagate as expanding cracks or as self-healing slip pulses, the role of elastic contrast on changes in fault-normal stress and rupture directivity, the influence of initial stress orientations and rupture velocity on a fault’s tendency to branch dynamically, and the off-fault damage produced by dynamic rupture propagation. Jim’s recent theoretical work on the role of friction and of pore pressure addresses one of the hottest topics in seismology and tectonophysics today, the origin and significance of episodic tremor and slip.

Jim is an extremely kind and gentle person and a delight to work with. He not only writes excellent and readable papers, he gives lectures of exceptional and legendary clarity on very complex problems. Jim is not only an intellectually gifted individual, he works nearly non-stop. As an example to others with lesser talents, which includes most of us, he is an inspiring example.

–Terry E. Tullis, Brown University, Providence, R.I.

Response

Thank you Terry, for those generous remarks, also for easing me into geophysics many years ago at Brown, and for the friendship and wonderful exchanges on friction, lab things, faulting, and earthquakes over the years since.

Charles Frank of Bristol, a personal hero who contributed greatly to geophysics, also pioneered understanding of line defects, called dislocations, in crystals. Those defects enable plastic flow, reproduce, and facilitate growth. Frank had a famous quip about crystals, defects, and people which, given the focus of the Bucher Medal, I could paraphrase as “the crust and lithosphere are like people: it’s their faults that make them interesting”

My route to faults was circuitous: I came as an engineering PhD from Lehigh to Brown in 1964 with a strong grounding in continuum mechanics and related mathematics. At Brown I built expertise in materials physics and directed that toolbox to cracking and plastic flow in engineering metals. That went well but, gradually, I decided to focus some on Earth processes too.

I didn’t have a clear idea how to do that but, with brilliant students and colleagues, tried to understand why deformation of soils and rocks is often localized into shear bands or faults, how pore fluid infiltration would interact with dilatancy of such media, causing time-dependent failures, and how that might underlie progressive extension of slip surfaces in landslides. Around then the dilatancy mania hit earthquake science. One couldn’t help reading, even in newspapers, about rock dilatancy, pore fluids, and earthquake prediction being just around the corner. I realized that I was developing just the tools to enter the fray.

That focused me on earthquakes, or at least half of me: I continued, at Harvard too where I moved in 1981, a juggling act, staying simultaneously active on fracture in both seismology and engineering. Gradually, since the new century, I seem to have shifted entirely to Earth science, now including, along with earthquakes and a bit on tsunamis, mechanisms enabling rapid ice sheet motion and topics intermingling geomechanics and hydrology.

I deeply appreciate how welcoming and encouraging the geophysics community was. My toolkit was surely as relevant there as in engineering, but I was without credentials and had gigantic gaps in knowledge, some occasionally exposed as unfilled still. That welcoming group, beyond Terry and his colleagues at Brown, includes marvelous people at USGS starting with Bill Stuart and then a host of others that I better not try to name, Paul Segall and his colleagues in geophysics at Stanford, and many others. I’ve been blessed too with some wonderful colleagues at Harvard and Brown.

Most of all, I have a soulmate in life, a seismologist with equal passion for all things relating to earthquakes and the like, and for many more placid things too, music not the least, that being my wife, Renata Dmowska.

Should I close with something for the young, like the incredible power of getting a strong grounding in math, mechanics, and other physics theory, which perhaps worked for me, or instead just ask them for help swimming into the modern data-swamped era?



–James R. Rice, Harvard University, Cambridge, Mass.

Paul F. Hoffman was awarded the 2010 Walter H. Bucher Medal at the AGU Fall Meeting Honors Ceremony, held on 15 December 2010 in San Francisco, Calif. The medal is for “original contributions to the basic knowledge of the crust and lithosphere.”

Citation

Over the past 5 decades, Paul Felix Hoffman has profoundly changed our understanding of the origin and evolution of the continental crust and lithosphere by field mapping, regional synthesis and interpretation, and relentless hypothesis testing.

Paul has spent 48 seasons in the field and 25 of those in the Canadian Shield. For his Ph.D. studies at Johns Hopkins University and his early years at the Geological Survey of Canada (GSC), Paul worked on the spectacularly exposed rocks in the east arm of Great Slave Lake. Subsequently, he examined a transect across the Paleoproterozoic Coronation geosyncline and argued in several influential papers that plate tectonics was active at that time and remarkably similar to today’s regime. These papers are even more remarkable when we consider that it was at a time when modern—day plate tectonics had still not been widely accepted.

This work was followed by a decade of understanding the history of the Coronation geosyncline, later named Wopmay orogen. His earlier synthesis, based on reconnaissance, made a number of testable predictions, and Paul set out to falsify his own ideas. Paul recognized that the zonation of the belt could be interpreted in terms of a model involving rifting, passive margin subsidence, arc magmatism, and collision. He led teams of students, coworkers, and colleagues during an intense decade of investigation. When he published his first Wopmay synthesis, in 1980, Precambrian geology was mired in nonactualistic models for crustal evolution, with few based on detailed mapping and regional synthesis.

The lessons learned in Wopmay orogen and the recognition of the power of synthesis led Paul to expand his approach to the Precambrian of Laurentia and the history of supercontinents; his approach was transformative. Hoffman’s iconic map of Laurentia made it clear that the anastomosing Proterozoic orogenic belts between Archean cratons recorded the consumption of oceanic lithosphere, the collision of continental fragments, and the stabilization of large cratons underlain by cold, buoyant lithospheric mantle. The recognition of short—lived collisional events that produced a vast orogenic collage was a radical departure from crustal reworking and long—lived ensialic orogenesis in vogue over the previous decades.

Following his Laurentian synthesis, Paul went to Namibia to better understand Pan—African orogens and the amalgamation of Gondwana but was sidetracked by the remarkable juxtaposition of Neoproterozoic glacial deposits with platformal carbonates. Here Paul began a new phase of his career, applying the tools of field geology with isotope geochemistry, geochronology, and plate reconstructions to understanding Neoproterozoic Earth history. Within 2 years he was to develop the snowball Earth hypothesis to a level of detail way beyond Kirschvink’s original hypothesis. He built a comprehensive, multidisciplinary hypothesis that led to a series of landmark papers and perhaps, more important, set an example of how to integrate tectonics, climate science, biology, and geology for a new generation of scientists.

Overall, Paul Hoffman has had a profound influence on our understanding of the origin and evolution of continental lithosphere, from its early assembly to glaciation and weathering. He is richly deserving of AGU’s Walter H. Bucher Medal.

—SAMUEL A. BOWRING, Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge

Response

Thank you, Sam, for those memories; and thank you, AGU, for recognizing the fruits of field geology.

I was lucky to be born a buster. Busters were the generation before the boomers. There weren’t very many of us, yet opportunities were everywhere because of the postwar economic and demographic boom. It was easy for us to stand out and get ahead.

As a buster geologist, I was also lucky to be in the last generation that remembers the world before plate tectonics. I am proud that a geophysicist, Dick Gibb, and a team of geologists were soon able to independently confirm the deep antiquity of plate tectonics, in the Canadian Shield.

The work recognized here was done while I was at GSC, where I had the enthusiastic support of directors—general Yves Fortier, Digby McLaren, Bill Hutchison, and Ray Price. I was lucky that GSC granted me leaves without pay to teach for a term or a year at a time and that I was welcomed at University of California, Santa Barbara; California Institute of Technology; University of Texas at Dallas; and Lamont Doherty. I was lucky also that two midlevel managers, Bill Padgham and John McGlynn, in different government departments found resources to support many Ph.D. thesis projects in and around the area I was geologically mapping. Among the beneficiaries were Larry Aspler, Sam Bowring, Mike Easton, John Grotzinger, Robert Hildebrand, Todd Housh, Brad Johnson, Charlie Kerans, André Lalonde, Janet King, Dave McCormick, Brad Ritts, Gerry Ross, Marc St-Onge, Rein Tirrul, Mike Villeneuve, and my mapping projects. Sam mentioned “relentless hypothesis testing.” It’s true; the hypotheses were inspired by the mapping, and Sam did the relentless testing. Any proper tectonic model can be falsified with a few good dates.

I was luckiest of all when Lillian McGlynn convinced Erica Westbrook to give me a second look. Erica and I have been happily married for 34 years this month, despite moves that were mostly not of her own choosing. It was not luck that I got a lot done; I had help.

As students in the early 1960s, we were advised to steer clear of tectonics because it was “dead.” For those who follow advice better than I did, look for a field that’s dead. The longer it’s been dead, the better. With luck, it’s not dead; it’s dormant. If you can wake it up, you will have as much fun as I’ve had recently with snowball Earth.

—PAUL F. HOFFMAN, School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia, Canada

Mark D. Zoback was awarded the 2008 Walter H. Bucher Medal at the AGU Fall Meeting Honors Ceremony, held 17 December 2008 in San Francisco, Calif. The medal is for “original contributions to the basic knowledge of the Earth’s crust.”

Citation

Mark Zoback is an outstanding geophysicist who has made fundamental contributions to the study of the global stress field, fault zone properties, crustal mechanics, and carbon sequestration. His work is consistently creative and original and has led to highly cited publications that address long-standing scientific questions.

Mark was a leader in establishing the scientific basis for the famous World Stress Map. The development of this map, led by his wife, Mary Lou, built on 15 years of collaborative efforts. He and Mary Lou were the first to show that stress orientations are regionally consistent and permit the definition of broad-scale regional stress patterns of tectonic significance. The scientific implications of global and regional stress patterns are profound and continue to stimulate new research. Observations of stress from deep wells and boreholes, using techniques pioneered by Mark and his colleagues, form the backbone of the World Stress Map and account for about two thirds of the database.

Mark is well known for his coleadership of the San Andreas Fault Observatory at Depth (SAFOD) project to drill into, sample, and monitor the San Andreas fault zone and for his role in establishing the International Continental Scientific Drilling Program (ICDP). Mark and his colleagues were able to uncover revolutionary empirical evidence that supports specific mechanical models of earthquake nucleation and propagation. In addition, Mark’s team collected intact fluid and rock samples along an active portion of the San Andreas fault. The analysis of these samples, which has revealed the presence of highly compacted, cohesionless rock that has undergone extensive cataclasis, provides a vivid snapshot of the dynamic history of the fault.

Mark’s work relating the state of stress in the brittle crust to fluid flow through critically stressed faults and fractures has led to exciting and unanticipated discoveries applicable at crustal and reservoir scale. Reservoir Geomechanics, his recently published seminal work, is an essential resource for reservoir geologists and engineers and others attempting to obtain knowledge of stress and mechanical processes at depth.

During the past decade, Mark has used his expertise in geomechanics and reservoir simulation to investigate CO2 injection into deep saline aquifers, depleted oil and gas formations, and unmineable coal seams. Mark’s analysis of the geomechanical implications of carbon sequestration lays important groundwork for assessing both the environmental and seismic risks and benefits of CO2 injection.

Mark has been a true scientific leader, providing direction to numerous prominent organizations, international programs, and advisory bodies. He is an excellent teacher, one who demands a lot from his students but who also constantly encourages. At Stanford for the past 24 years, he has maintained a lively interaction with his outstanding colleagues there and at the nearby U.S. Geological Survey.

In summary, Mark Zoback has made important contributions to our understanding of how processes related to plate tectonics, earthquakes, and CO2 sequestration are affected by various forces within the Earth’s crust. Through his initiative, large scientific operations such as ICDP and SAFOD have become extremely successful in advancing our fundamental understanding of the Earth’s crust, both in plate interiors and at active fault margins.

These accomplishments, and his success at solving complex and challenging problems, make him a very deserving recipient of the AGU Walter H. Bucher Medal.

—WALTER D. MOONEY, U.S. Geological Survey, Menlo Park, Calif.

Response

Mark Zoback is an outstanding geophysicist who has made fundamental contributions to the study of the global stress field, fault zone properties, crustal mechanics, and carbon sequestration. His work is consistently creative and original and has led to highly cited publications that address long-standing scientific questions.

Mark was a leader in establishing the scientific basis for the famous World Stress Map. The development of this map, led by his wife, Mary Lou, built on 15 years of collaborative efforts. He and Mary Lou were the first to show that stress orientations are regionally consistent and permit the definition of broad-scale regional stress patterns of tectonic significance. The scientific implications of global and regional stress patterns are profound and continue to stimulate new research. Observations of stress from deep wells and boreholes, using techniques pioneered by Mark and his colleagues, form the backbone of the World Stress Map and account for about two thirds of the database.

Mark is well known for his coleadership of the San Andreas Fault Observatory at Depth (SAFOD) project to drill into, sample, and monitor the San Andreas fault zone and for his role in establishing the International Continental Scientific Drilling Program (ICDP). Mark and his colleagues were able to uncover revolutionary empirical evidence that supports specific mechanical models of earthquake nucleation and propagation. In addition, Mark’s team collected intact fluid and rock samples along an active portion of the San Andreas fault. The analysis of these samples, which has revealed the presence of highly compacted, cohesionless rock that has undergone extensive cataclasis, provides a vivid snapshot of the dynamic history of the fault.

Mark’s work relating the state of stress in the brittle crust to fluid flow through critically stressed faults and fractures has led to exciting and unanticipated discoveries applicable at crustal and reservoir scale. Reservoir Geomechanics, his recently published seminal work, is an essential resource for reservoir geologists and engineers and others attempting to obtain knowledge of stress and mechanical processes at depth.

During the past decade, Mark has used his expertise in geomechanics and reservoir simulation to investigate CO2 injection into deep saline aquifers, depleted oil and gas formations, and unmineable coal seams. Mark’s analysis of the geomechanical implications of carbon sequestration lays important groundwork for assessing both the environmental and seismic risks and benefits of CO2 injection.

Mark has been a true scientific leader, providing direction to numerous prominent organizations, international programs, and advisory bodies. He is an excellent teacher, one who demands a lot from his students but who also constantly encourages. At Stanford for the past 24 years, he has maintained a lively interaction with his outstanding colleagues there and at the nearby U.S. Geological Survey.

In summary, Mark Zoback has made important contributions to our understanding of how processes related to plate tectonics, earthquakes, and CO2 sequestration are affected by various forces within the Earth’s crust. Through his initiative, large scientific operations such as ICDP and SAFOD have become extremely successful in advancing our fundamental understanding of the Earth’s crust, both in plate interiors and at active fault margins.

These accomplishments, and his success at solving complex and challenging problems, make him a very deserving recipient of the AGU Walter H. Bucher Medal.

—WALTER D. MOONEY, U.S. Geological Survey, Menlo Park, Calif.

E. Bruce Watson was awarded the Walter H. Bucher Medal at the AGU Fall Meeting honors ceremony, which was held on 13 December 2006 in San Francisco, Calif. The medal recognizes original contributions to the basic knowledge of crust and lithosphere.

Citation

It is with great pleasure that I introduce Bruce Watson as this year’s recipient of the Walter H. Bucher Medal. This honor comes at an opportune moment, as 2006 represents the thirtieth anniversary of Bruce’s first publications on the role of silicate melt structure in trace element partitioning. As always, Bruce’s approach to the problem was original, in this case investigating mineral-melt partitioning by simply eliminating the mineral, and instead focusing the distribution of trace elements between immiscible melts. In 2006, a conceptually identical paper appeared in the pages of Science. This affords a quantification not often observed at awards ceremonies: Exactly how far ahead of his time was Bruce Watson? The answer is, 30±1 years.

Bruce has been honored many times, and I have been fortunate to have either coauthored or edited a number of previous citations. The most economical approach to the task is to simply take previous citations and change the adjectives. One citationist referred to Bruce as a ‘taciturn Yankee.’ I much prefer ‘reserved son of the Granite State.’ Another, at least in draft, discussed the fastidious manner in which Bruce runs his lab. A number of Freudian terms were used. Instead, I like the sound of ‘Bruce is meticulous and well-organized, and capable of instilling those qualities in others.’

Experimental geochemists have necessarily focused much effort on phase equilibria and partitioning, and Bruce continues to make important contributions in this area. However, Bruce has also gained distinction as one of the leaders in bringing dynamics to experimental geochemistry in the form of kinetics and mass transfer. With apologies to Bowen and a handful of others, we knew virtually nothing about diffusion in magmas and minerals 30 years ago. Bruce was the first to characterize the effects of pressure and volatile content on diffusion in melts, and his elegant experiments inspired a generation of geochemists. Similarly, although we blamed aqueous fluids for a lot, we knew little about their microstructural distribution in crustal and upper mantle rocks, a parameter that is essential to understanding fluid transport and the effects of fluids on physical properties. As in his studies of diffusion, Bruce’s efforts isolated the important parameters and developed the interpretational framework for those that followed.

Another of Bruce’s signature contributions concerns the role of accessory minerals in crust and mantle petrogenesis. Unlike fluids, which were blamed for a lot, accessory minerals were largely ignored. With Mark Harrison, Bruce developed a set of ‘accessory phase parameters’ describing accessory phase solubility, trace element partitioning, and controls on the approach to equilibrium. These parameters defined that utility of accessory minerals in petrogenetic investigations. Most recently they have transformed zircon, our premiere geochronometer, into a new geothermometer based on titanium solubility and used the temporal and thermal information contained in the Earth’s oldest minerals to redefine our view of the Hadean Earth.

The one constant in Bruce’s work is that his experiments always look so simple—at least after the fact. His work is characterized by its elegance and economy and is performed in a style totally his own. His contributions span the boundaries between petrology, geochemistry, and mineral physics, but more often than not, he succeeds in making those boundaries transparent. It is a great pleasure to honor Bruce’s continuing contributions to our knowledge of the Earth’s crust and lithosphere and to present him for AGU’s Walter H. Bucher Medal.

—F. J. RYERSON, Lawrence Livermore National Laboratory, Livermore, Calif.

Response

I am deeply honored to be the recipient of this year’s Walter H. Bucher Medal, and I am humbled by the company I am joining.

In his generous comments, Rick Ryerson noted that 2006 marks the thirtieth anniversary of my first publications. This is amazing, perhaps to me more than anyone. I have to accept the written record, but I also see more things I have to do in the next 5 years than I did back in 1976. Whether or not you accept Rick’s characterization of me as ‘taciturn’ or just ‘reserved,’ those of you with whom I have worked closely know that when it comes to science (and a few other things) I am still quite energized.

Both geochemistry and my perspective on it have evolved a great deal in the past 30 years, and I am increasingly inclined to inflict advice on young scientists and students. I think it is vital that scientists of all ages be able to anticipate, detect, and respond to change; somehow the education and attitude we impart to our students should build in these abilities.

Perhaps the greatest change in my 30-year career has been in the funding climate. I see a striking incongruity in the geosciences today: On the one hand, there has not been a more exciting time for our science, but on the other hand there have never been fewer funds to support that science. This dichotomy filters down to young scientists in ways that are both obvious and subtle. Consider, for example, a dean or department head who advises a new assistant professor that ‘scientific collaboration is essential, but be sure to make your own mark.’ The same hard-to-decipher signals are apparent in the organization of federal funding programs, where ‘multidisciplinary’ is advertised as the way to do science, but most practitioners understand that individual knowledge, insights, and creativity are still crucial. It is essential that young scientists understand the complexity of the terrain they will have to navigate, mainly so they will not be daunted by it.

The most effective beacon for younger and older Earth scientists alike is the realization that those of us who have knowledge about the Earth have an obligation to maintain the passion and vigor of our fields. Two of the most challenging issues the world now faces—environment and energy—are inseparably interwoven with the Earth sciences, and expanding the knowledge of our discipline will be essential for decades to come.

There are a great many people to thank for the roles they played in my being here today, including family, friends, mentors, colleagues, and students. Because I can not thank all of them individually, I will just say that I feel very fortunate to have all of you in my life. You know who you are.

—E. BRUCE WATSON, Rensselaer Polytechnic Institute, Troy, N.Y.

Mervyn S. Paterson received the Bucher Medal at the 2004 Fall Meeting Honors Ceremony on 15 December, in San Francisco, California. The medal is given for original contributions to the basic knowledge of the crust and lithosphere.

Citation

It is the nature of modern research in the Earth sciences that observations of natural phenomena are often made and interpreted through the prism provided by the enabling sciences and technologies. Thus it has been with Mervyn Paterson’s career. His undergraduate training in engineering in Adelaide formed the basis for his Ph.D. study of X-ray line-broadening in cold-worked metals under Orowan at Cambridge. This interest in the deformation of metals was fostered during his employment at the Aeronautical Research Laboratories in Melbourne and by postdoctoral experience at the Institute of Metals at the University of Chicago. Mervyn’s general background in engineering and his particular interest in mechanical behavior have underpinned a distinguished career at the Australian National University in the experimental deformation of rocks, providing fundamental new insight into the mechanical behavior of the Earth’s crust.

The study of rock deformation required the development of high-pressure techniques’ initially at room temperature and, from the 1960s, at high temperature. The progressive enhancement of the capabilities of Mervyn’s deformation machines has required solutions to several major technical challenges. Most significant among these have been internal heating and measurement within the pressure vessel of load and piston position, and arrangements for torsional deformation at both the microstrains of seismic wave dispersion and attenuation and the very large strains sometimes encountered in natural rock deformation. It is no small testimony to the quality of Mervyn Paterson’s designs that his high-temperature testing machine has become the instrument of choice for experimental rock deformation worldwide.

Mervyn’s development of versatile equipment for experimental rock deformation has been motivated by a desire to understand the mechanical behavior of the Earth’s crust and a keen interest in material behavior more generally. His experimental studies of that distinctive class of materials known as rocks and minerals, supported by relevant theory, have provided insight into many naturally occurring phenomena. These range from folding and fabric development to dehydration embrittlement as a possible cause of earthquakes, from changes in porosity and permeability associated with dilatant behavior to the constitutive laws for high-temperature plastic deformation, from water weakening of quartz to geological applications of nonhydrostatic thermodynamics.

As a role model for his students and colleagues over many years, Mervyn Paterson has set a consistently formidable standard. He always shuns the superficial, instead showing the determination and persistence required to expose and illuminate the essentials of the subject. In particular, he has invariably sought to develop microstructural explanations for observed macroscopic mechanical behavior. Remarkably, he maintains a refreshing, youthful openness to new ideas’even now in his 80th year.

Published in 120 journal articles and his 1978 classic Experimental Rock Deformation: The Brittle Field soon to appear in second edition coauthored by Teng-Fong Wong, Mervyn Paterson’s research has made a major and lasting impact on the field of experimental rock deformation and on our understanding of the Earth’s crust. He is indeed a worthy recipient of the Walter H. Bucher Medal.’

—IAN JACKSON, Australian National University, Canberra

Response

Thank you, Ian, for your kind words, and thank you, AGU, for this auspicious recognition. When I look at the illustrious list of previous recipients of the Walter H. Bucher Medal, I am especially conscious of what an honor it is to be chosen to join this group. And I am particularly impressed to note that three of this group have been rock deformers, Dave Griggs, John Handin, and Bill Brace, all of whom have been my good friends and colleagues over time.

One only gets to be standing here through the support and generosity of many people. I come from a small-scale farming background, and I am enormously appreciative of the opportunity afforded by my parents’ encouragement to undertake university studies. I was lucky over the years, first at one-teacher country schools and later at a city high school and at university, to have very supportive and inspiring teachers. And since then I have enjoyed the support, encouragement, and friendship of many colleagues, far too many to name here. However, I must mention the loving support of my wife of 53 years, Katalin, and our children, Barrie and Elizabeth, and I am very happy that Elizabeth is here on this occasion.

What are some of one’s reflections on the passage of these years? One point is the importance of having as general an educational background as possible so as to adapt to changing demands. As Ian has alluded to, I started off studying extraction metallurgy, which was basically an engineering course at Adelaide University, but then I switched to metal physics and finally went over from deforming metals to deforming rocks. I once heard Frank Turner describe me as “a metallurgist gone wrong.” However, the important thing for flexibility in scientific research is to have an adequate fundamental underpinning of mathematics, physics, and chemistry. Anything can then follow.

Another thing that strikes me is the increasing pace of life over the years. It seems that there has come to be less time for family, for hobbies, for reading, for travel, and so forth. Instead, there is a relentless push to be more competitive, to produce more papers. Perhaps in part, it reflects pressures from a dramatically increasing population in a finite Earth.

Finally, I count it an enormous privilege to have been able to spend most of my life doing research in scholarly institutions, mainly at the Australian National University. It is, of course, great if one’s research has some practical applications, and I am very conscious of this, but it is also great to be able to do basic research for its own sake, as adding to humanity’s stock of knowledge and understanding of the world we live in. In this connection, I would like to express an appreciation of AGU as a great organization that among its multifaceted activities, promotes fundamental research. One of its stated aims is “to promote the scientific study of Earth and its environment in space and to disseminate the results to the public.” May it long continue to do so.’

—MERVYN S. PATERSON, Australian National University, Canberra

Stuart Ross Taylor was awarded the 2002 Bucher Medal at the AGU Fall Meeting Honors Ceremony, which was held on 8 December 2002, in San Francisco, California. The medal is given for original contributions to the basic knowledge of the Earth’s crust and lithosphere.

Citation

“I don’t quite remember when I first met Ross Taylor, but it was a long time ago, and I am almost certain it was in a noisy pub over some beers. I was a young and eager beaver then, and Ross was the elder statesman geochemist. Ross always mumbled a little, and I did not understand most of the things he said. But I liked him a lot. It seemed that, unlike most geochemists, he was a genuinely nice guy. Well, I am no longer all that young, but to me, Ross is still the quintessential elder statesman, a man of encyclopedic knowledge and deep understanding of geochemistry and of our planet and its neighbors. Ross has been around for more than three-quarters of a century, and I am confident he is planning to be around for at least another quarter. I am deeply honored that he has asked me to read this citation.

“Ross was born and raised in New Zealand, and he received his bachelor’s and master’s degrees at the University of New Zealand. After that, he became a world traveler, spending virtually his entire adult life abroad. His travels took him to the United States, where he received his Ph.D. degree under the supervision of Brian Mason. That was not enough; he went on to earn a Master of Arts, while working as a ‘demonstrator’ at Oxford. From there, he went on to become Senior Lecturer in Geochemistry at the University of Capetown, and he finally settled down, more or less, at the Australian National University as Professorial Fellow until he retired to become Emeritus Professor.

“Ross is looking back, and forward, at an un-finished career of enormous scientific breadth and scholarship as well as truly fundamental contributions. His scientific opus is astounding and humbling. He has published about 230 papers on the subjects of lunar geochemistry, meteorites, cosmochemistry, trace elements in volcanic and sedimentary rocks and minerals, analytical methods, and about continental composition and evolution. On the side, he has written nine books on subjects like solar system evolution, the Moon, and most important today, The Continental Crust: Its Composition and Evolution.

“Ross has received many awards, including the Norman Bowen Award by the AGU in 1988, the Goldschmidt Medal of the Geochemical Society in 1993, the Gilbert Award in planetology by the Geological Society of America in 1994, and the Leonard Medal of the Meteoritical Society in 1998. Today, he receives the Walter Bucher Medal ‘for original contributions to the basic knowledge of Earth’s crust.’ On this subject, he has not just been a pioneer. He is the pioneer. Thirty-five years ago, Ross wrote a classic paper on ‘the origin and growth of continents,’ and this was just the first of 30 papers on the subject. He developed the ‘andesite model’ of the continental crust, which derives the crust by accretion of arc volcanic rocks. He refined this model by taking special account of Archaean rocks, which he showed differ systematically in their geochemistry from younger rocks. He concluded that about 75% of the present-day crust was in place 2.5 billion years ago.

“Why should anyone care about the chemical composition of the continental crust? Well, it turns out that this composition matters to almost everything else. Ross realized that 30 to 50% of the Earth’s total budget of highly incompatible elements, including all the heat-producing elements, reside in the crust. This has enormous ramifications for understanding the Earth and its evolution as a whole. The machinery that distilled these elements with such efficiency into a thin layer of scum floating on top of the mantle is still not fully understood. A few years ago, most geochemists were happy with the notion that the depleted complement of the continental crust is confined to the upper third of the mantle. But now, the witch doctors practicing seismic tomography tell us that subduction continues all the way into the lower mantle. What goes down must come up, and therefore the Earth cannot maintain a neatly layered mantle. Thus, knowing exactly what’s on top is crucial to knowing what’s still down there and what isn’t. So the composition of the crust is crucial to any full understanding of the Earth’s mantle and its evolution. Ross summarized these relationships with an ingenious and utterly simple diagram that relates ionic radius and valency of any lithophile element to the degree of enrichment in the crust. This diagram is a direct descendant from the principles of geochemical substitution laid down by Goldschmidt two scientific generations earlier. Perhaps this is not surprising, considering there is also a line of descent from Victor Goldschmidt via Brian Mason to Ross Taylor. Ross is not resting on his laurels. His most recent paper on the composition of the Earth’s crust was published last year.

“As emeritus professor, Ross has reverted to his favorite occupation, namely, that of a ‘demonstrator.’ He is the human demonstration of the Heisenberg uncertainty principle: at any given time, and if you are lucky, you might encounter him on some university campus or at some pub. Then you know where he is at the moment, but not necessarily where he is going next, but it seems unlikely that he will ever stop working on and writing about the continental crust. It is a great pleasure to honor Ross Taylor’s seminal and continued contributions to the basic knowledge of Earth’s crust, and to present him for the Walter Bucher Medal of the AGU.”

—ALBRECHT W. HOFFMANN, Max Planck Institut für Chemie

Response

“Thank you, Al. When I grew up in New Zealand, on a farm, there were so few people around that I never had to raise my voice, except to call to my sheepdog, so it became a habit.

“Well, it is a great honor to receive the Bucher Medal, coming as it does from such a distinguished academic society and commemorating Walter H. Bucher. I thank the society for this distinguished award.

“I owe much to my parents, who encouraged me and who made sure that I received a good education. My wife, Noël, has been a constant support in my work. Without her backup on the home front, I wouldn’t have been able to travel so much.

“But of course, such awards do not arise from one individual’s work. The message is to always have good colleagues. I was fortunate to encounter Scott McLennan at an early stage of my studies on the crust. Now we have just finished our 40th joint paper with never a cross word. Roberta Rudnick also has made substantial contributions in lots of ways.

“As a graduate student in Indiana, where Brian Mason then was, I proofread the first edition of Brian’s famous book, Principles of Geochemistry. There, I learned that Goldschmidt had worked out a crustal composition by analysing sediments from glacial lakes. So I realised that the solution to finding the composition of the crust was to let nature grind up the rocks for you, rather than trying to collect tens of thousands of samples. The crustal history is all there in the sedimentary rocks if only you can read it.

“It was Harold Urey who got me interested in the Moon, the other planets, and the great debate over whether tektites came from the Earth or the Moon. He gave me the useful advice to work always on important problems and not to admit that you are wrong too soon.

“So all this gave me a broader perspective. There doesn’t seem to be anything like our useful continental crust, which is the product of plate tectonics, elsewhere in the solar system. Given the many chance events that have resulted in forming the crust on this planet, I wonder just how unique our crust is in the universe. This has particular significance, as such crusts are probably a necessary feature for any planet that intelligent creatures or little green men could live on.

“In conclusion, I would like to pay a special tribute to the hospitality, openness, and goodwill of this great country. It is here that I have made much of my career, particularly in lunar and planetary sciences. Although I come originally from New Zealand and now from Australia, I have always been made entirely welcome in this country where I have always felt very much at home. It is in such free secular societies that science is able to flourish so well, with great benefit for everyone.”

—STUART ROSS TAYLOR, Australian National University

James H. Dieterich was awarded the 2002 Bucher Medal at the AGU Fall Meeting Honors Ceremony, which was held on 8 December 2002, in San Francisco, California. The medal is given for original contributions to the basic knowledge of the Earth’s crust and lithosphere.

Citation

“James H. Dieterich has revolutionized the understanding of frictional processes in rocks, their description by constitutive relations, and implications for earthquake nucleation and seismicity rate changes. His development of this new understanding of the Earth’s crust makes him a deserving recipient of the Walter Bucher Medal.

“Born in 1942, Jim grew up in Seattle and studied geology at the University of Washington. He went on to graduate studies in geology and geophysics at Yale and finished his Ph.D. in 1968 on numerical models of finite amplitude folding.

“His first job was at USGS in Menlo Park, and he must have liked it because he has been there since, serving stints along the way as Chief of the Branch of Tectonophysics and Chief Scientist of the Earthquake Hazards Team. He has led or participated in USGS probabilistic assessments of earthquake risk in California and was recognized with a Department of Interior Superior Service Award in 1990.

“Jim came to USGS in the early days of the National Earthquake Hazards Reduction Program, to develop numerical earthquake models. He soon realized that friction constitutive laws were key to physically realistic earthquake models. This led him into the lab and to his tremendously influential series of papers on rock friction. Early work, confirming the dependence of friction on time of static contact, led to the development of his ‘velocity stepping tests,’ in which time dependence of friction following step changes in velocity was recorded.

“One of the best pieces of advice I ever gave to a student was to cross the continent to work for awhile with Jim Dieterich. I had just heard him report on his ideas at a small discussion group in the late 1970s and was blown over, because here was a scientist who was clearly on the threshold of developing a rational mechanics of frictional instabilities. That seemed very important for understanding earthquakes. The student was Andy Ruina, and, under Jim’s inspiration, his presence soon led to the concept of constitutive laws for friction, which contain a state variable or variables to account for the evolving condition of the population of asperity contacts. Those are known now as “Dieterich-Ruina” friction laws or as ‘rate- and state-dependent’ laws.

“That formulation allowed explanation of conditions under which slip is stable or unstable in lab apparatus, and it provided a convincing way of understanding the depth distribution of seismicity as a rate-weakening to rate-strengthening transition with temperature increase. Jim took things a major step forward in 1994, by using the friction laws to explain the relation between earthquake stress changes and seismicity rate changes. He showed how critical stress changes can produce a self-driven state of accelerating creep on faults and, through an insightful application to a statistical array of fault segments, provided a physical derivation of the well-known Omori empirical law of aftershock decay.

“His approach, while initiated for the understanding of faulting in rocks, has proven equally valuable for all solids studied, metals, plastics, wood, and even paper, and has broadly influenced modern tribological research and understanding.

“Jim conducted ingenious experiments to understand the micromechanical processes that give rise to the observed macroscopic behavior. Working with Brian Kilgore, he used optical methods to show that the characteristic sliding displacement for strength transitions in transparent materials, including quartz, calcite, and glasses, is that needed to establish a new population of asperity contacts. This puts the evolution effect in the constitutive laws on a solid physical basis.

“Jim also made seminal contributions to volcanology. His finite element studies with Bob Decker showed that comparison of vertical to horizontal displacement measurements was essential to even weakly constrain the shape of a compact magma chamber. He authored an influential paper on the stability of volcanic flanks and showed that flank motion is required in order for rift zones to persist over geologic timescales, as on the Hawaiian shields. Very recently, he has combined his interests, interpreting seismicity rate changes at Kilauea by friction theory in order to constrain stress changes from magmatic intrusion.

“For all of those reasons, it is clear that Jim Dieterich is a fitting recipient of the Bucher Medal.”

—JAMES R. RICE, Harvard University, Cambridge, Mass.

Response

“Thank you, Jim, for your very generous comments.

“I must begin by acknowledging my dear wife, Susan, who is my biggest booster, most trusted advisor, and, at times, necessary critic.

“Research is never done in a vacuum. We build on the work of others, we are aided and supported by colleagues, and we rely on the organizations and institutions to create the opportunities that enable us to do research. Also, our accomplishments are shaped by teachers and the silent influence of role models. I have been fortunate in each of these areas.

“After finishing a Ph.D. at Yale, I came to the U.S. Geological Survey and joined the newly formed earthquake seismology group in Menlo Park. It was a good decision. Over the years the USGS opened a wonderful range of research opportunities for me, and provided a very rare environment where long-term and risky research efforts could be pursued. Its an honor and pleasure to work with such a wonderful group of distinguished and dedicated scientists.

“An initial effort of mine at the USGS was to develop dynamical finite element models of the earthquake source. At that time, and in comparison with current capabilities, even big computers were rather limited, so those models were pretty pitiful by today’s standards. However, beyond the computa-tional limitations, I was really troubled by the fact that there were no verified fault constitutive formulations appropriate to the task. Simply put, we were using invented properties that yielded earthquake-like simulations, and consequently, our models had a dubious foundation and limited predictive value.

“Jim Rice mentioned that I turned to the laboratory to try to develop a better understanding and description of frictional properties that could be used to model earthquake processes. What he did not say was that I was essentially clueless about laboratory technique and instrumentation. Fortunately, several people, especially Steve Kirby, provided substantial help and guidance that set me in the right direction. As the experimental effort evolved, Paul Okubo joined the project and did some first-class work, before moving on to become a volcano seismologist. Currently, nothing in the lab happens without Brian Kilgore.

“At first, our reports of subtle and somewhat bizarre frictional effects, and my claims that these effects may control some fundamental earthquake processes, encountered some frictional resistance in the research community. However, I must point out that Jim Rice, Terry Tullis, and Andy Ruina, who were all at Brown University at the time, immediately picked up on it. Their major theoretical and experimental contributions to the subject have had a great impact on the field, and on me, over a span of 20 years. This wonderful recognition tonight must also reflect their contributions.

“Currently, I am enjoying interactions with two groups. The first is led by Ross Stein, and we are looking at the effects of earthquake stress interactions by applying the earthquake rate formulation that comes from rate- and state-dependent friction. One effort of this group is to develop physically based and region-specific estimations of the well-known transient jump in earthquake probabilities that follows large earthquakes. The second includes Valérie Cayol of Laboratoire Magmas et Volcans, Université Blaise Pascal, and my long-time colleague, Paul Okubo. We think it may be possible to use seismicity rate changes quantitatively as a stress meter. We’re pursuing this idea at Kiluaea Volcano, which must be one of the world’s finest natural laboratories for volcanic and earthquake processes.

“In conclusion, I will just relate the reaction of a good friend to the news that I would be the recipient of the Bucher Medal. He is not a geophysicist, and he took particular note that it is for research relating to the Earth’s crust. From this he decided that henceforth I should be referred to as a distinguished crustacean. I tried to tell him that the simple designation of geophysicist was preferable to crustacean, but so far, he’s ignored this repeated suggestion. But by whatever name the research is given, it has been a great pleasure to work with some marvelous people on processes that have a subtle, but strong control on some of the most dynamic processes in the Earth’s crust. Thank you all.”

—JAMES H. DIETERICH, U.S. Geological Survey, Menlo Park, Calif.

Norman H. Sleep was awarded the 2002 Bucher Medal at the AGU Fall Meeting Honors Ceremony, which was held on 8 December 2002, in San Francisco, California. The medal is given for original contributions to the basic knowledge of the Earth’s crust and lithosphere.

Citation

“Norman Sleep’s major contribution to geophysics has been to use simple physical ideas to understand processes at work within the Earth, particularly those affecting the crust and lithosphere. He entered geophysics soon after the discovery of plate tectonics and has made important contributions to most of the recent advances in our understanding of geodynamics. These contributions cover a great range of topics.

“Mid-Ocean Ridges (1969 to 1991). Sleep used the relationships between the depth of the ocean and the age of the underlying plate to infer the temperature dependence, which is now widely used. He was the first to point out that models of crustal generation on ridges that required large magma chambers to be continuously present beneath slowly spreading ridges were not compatible with heat conservation. Sleep’s simple models explained the differences between the axial valley at slow-spreading ridges and the axial high at fast-spreading ones and the differences in magma chamber geometry and crustal structure as a function of spreading rate. Sleep, with Wolery, first used heat flow data to estimate the volume and age distribution of the heat transferred by water flux through oceanic crust and showed how the hydrothermal fluid would affect the composition from seawater and play a key role in global geochemistry. He showed that magma chambers inferred from seismic imaging occur deeper than expected because much of the hydrothermal circulation occurs by low temperature off-axial flow.

“Continental Margins (1971-1980). Sleep was first to quantify passive margin subsidence, showing that the subsidence history of extensional continental margins closely resembled that of oceanic plates. This result was unexpected, since the continental crust that displayed this behavior was often very much older than the onset of the subsidence. Sleep was the first to realize that the stratigraphic sequence on passive continental margins could be modeled by deposition on a thermally subsiding rifted margin. His idea also had considerable implications for hydrocarbon exploration along margins and in continental interior basins.

“Subduction Zones and Island Arcs (1971-1979). Sleep looked at marine geophysical aspects like marginal basin formation and trench morphology and gravity and developed thermal and mechanical models important to understanding the subduction process and its implications for plate motions.

“Magmatism (1974-1991). Sleep first applied equations governing the two-phase flow of melt through a crystalline matrix. Developments from these equations have provided dynamical models for both magma generation and for metamorphism by fluid infiltration.

“Thermal Evolution of the Mantle (1979-1982). Sleep used petrological data to infer a cooling of the mantle by about 300°C over 3 Ga, and showed that K, U, and Th abundances in the mantle had to be less than 60<37> cosmic to be consistent with whole mantle convection and the observed atmospheric 40Ar.“Archaean Tectonics (1982-1992). Sleep, with Windley, inferred that higher mantle temperatures caused the Archaean crust to be appreciably thicker than the Phanerozoic, but that the geologic record of fault zones in cratons indicated a style of tectonics similar to plate tectonics.

“Martian Tectonics (1982-1994). Sleep, with Phillips, generated the most convincing model for the support of Tharsis–the greatest topographic and geoidal high on the terrestrial planets.

“Mantle Plumes (1987- ). Sleep has been among the leaders in investigating what seafloor topography tells about the thermal structure and flow dynamics of the mantle. With Richards and Hager, he used the bathymetry and gravity at the various hotspot swells as constraints on their fluid mechanics and hence on mantle dynamics. They thus estimated the flux and temperature of the upwelling plume material for different hotspots and thus addressed the relationship between plume processes and plate tectonics in mantle evolution. Using an elegant comparison of a plume-affected hotspot track to a nearby abyssal plain, Sleep argued for a common plume with time-varying flux to explain adjacent continental and oceanic features and thus infer the different responses of continental and oceanic lithosphere to hotspots. He used the shape of the Hawaiian swell to draw inferences about the plume flow and to explain why the lithosphere appears not to be significantly thinned beneath Hawaii. Most recently, Sleep has developed models of the influence of variations in lithospheric thickness on lateral flow of plume material to explain off-ridge topography and volcanism.

“Fault Mechanisms (1992- ). Sleep developed a formula for the coefficient of friction, taking into account porosity, fluid pressure, strain rate, and temperature. He applied this to fault models to infer histories of strain patterns, fluid flow, heat generation, and fracture, and explained why there is such a great range of fault failure, from creep at low shear tractions to sudden failure in major earthquakes.

“These diverse, but profound, efforts of Norman Sleep have greatly influenced many Earth scientists. He is keenly appreciated for both his physical insights (especially by geophysicists) and his attention to the observed record of the Earth (especially by geologists). The Bucher Medal ?recognizes original contributions to the basic knowledge of the Earth’s crust.’ When the medal was established in 1966, ?crust’ connoted to many the layer of mechanical strength as well as the layer of lower density composition. In this broader definition, certainly no one has been more original, or more diverse, than Norman Sleep in contributing to basic understanding of how the outermost layers of the solid Earth came to be: tectonically, thermally, and compositionally. Moreover, he has done this in ways that have not only been original, but also have been enlightening and useful to his colleagues.”

—WILLIAM M. KAULA, University of California, Los Angeles

Response

“Thank you, Bill. I was surprised when I opened the letter from AGU. I was even more surprised when I read on and found that the Bucher Medal is for the study of the Earth’s crust. I have not viewed myself as a crustal scientist. I believe that AGU is recognizing the importance of an integrated approach to crustal and global tectonic studies, rather than my actual contributions. I have had the good fortune to collaborate with many others and would have accomplished little without constant interaction. I cannot thank everyone in 3 minutes so I will describe how others have helped shape my view of the crust.

“As an undergraduate at Michigan State in 1967, establishment of a medal for study of the Earth’s crust would have made as much sense to me as the botany society having a medal specially for plants. I knew from taking Bill Hinze’s classes that much was inferred about the Earth’s deeper interior, yet interior processes had not been linked to the crust, the part of the Earth we could actually examine in detail. Robert Dietz had visited Michigan State and talked about seafloor spreading. The topic got me thinking, but it seemed that any resolution would be in the distant future. After discussing graduate schools with Dr. Hinze, I applied to and was accepted by the Massachusetts Institute of Technology.

“In the summer of 1967 I arrived at MIT in the middle of a scientific revolution. I attended the conference at Woods Hole where results establishing seafloor spreading were presented. With the advent of plate tectonics, the continental crust had suddenly become an unimportant passenger on plates. The oceanic crust had nice magnetic anomalies but was otherwise a 6-km- thick nuisance that got in the way of looking at mantle processes, whose physics was poorly understood. Well, if you didn’t like the oceanic crust, it would soon subduct anyway.

“Gene Simmons hired me to work in the laboratory that summer, preparing equipment to measure heat flow in the ocean basins. I was not much good in the lab, but I did become interested in the thermal structure and subsidence of oceanic lithosphere. When Dave Wones and Dick Naylor organized a seminar on the Appalachians, I ended up with the topic of the passive margin out of laziness. The presentation was to be on the last day and flat-lying sediments seemed simpler than folded mountains.

“I applied thermal contraction, which had worked so well at the ridge, in explaining the passive margin. It worked, despite the fact that I was so impressed with the fall line unconformity that I initially came to believe that surficial erosion thinned the crust instead of it stretching during continental breakup.

“Being from Michigan, I compared the subsidence history of that interior basin with thermal contraction curves, opening a can of worms that has persisted to the present day. However, this work was not leading to a thesis, and the military draft was blowing down my neck. I switched topics to work with Nafi Toksoz on subduction and island arcs. A thesis completed on the deep Earth, I arrived as an assistant professor at Northwestern University. I was again in the middle of the continent and determined to relate plate tectonics to what was going on. It had also become evident that the oceanic crust carried goodies into the mantle that might come up at island arcs.

“Pat Hurley had already shown that degassing of the Earth was related to plate tectonics. Robert Garrels and Fred Mackenzie were studying global geochemical cycles. The crust was now a long-term reservoir and recorder on the effects of complex chemical exchanges within the mantle. Tom Wolery was looking for a thesis topic involving the oxygen cycle. Independently, Bob Garrels and I suggested that he look at ridge hydrothermal systems. The days when one could think that altered basalt was merely dumped back into the ocean were rapidly ending.

“To cut to a recent topic, I did not consider mantle plumes to be a good explanation for hotspots when the hypothesis first came out. Instead, I preferred propagating cracks in the lithosphere. By 1984 I was determined to put plumes to rest and showed that mantle lithosphere delaminating from the base of the lithosphere would produce a positive long wavelength geoid anomaly. When I presented this at the AGU meeting, Mark Richards showed that mantle plumes could do the same thing in that session. We agreed to disagree at first. Soon we could explain a host of phenomena, as plumes are conduits of hot material, not candlelike heat sources under the lithosphere. Colleagues have continued to tweak my interest in plumes with geological problems. In this regard, I would also like to thank George Thompson, Tom Parsons, Mark Anders, and Cindy Ebinger.

“Since the Bucher Medal was established, we have found that the Earth’s crust is incredibly complex, and not just because we can examine it in detail. There are rocky and icy crusts on moons and other planets. The crust is a full active player in global tectonic and geochemical processes and the storehouse of the geological record

—NORMAN H. SLEEP, Stanford University, Calif.

Hiroo Kanamori was awarded the Walter H. Bucher Medal at the AGU Fall Meeting Honors Ceremony on December 17, 1996, in San Francisco, California. The Bucher Medal recognizes original contributions to the basic knowledge of the Earth’s crust.

Citation

“It is a pleasure to introduce the recipient of the Bucher medal, Hiroo Kanamori. We honor him for outstanding contributions in the use of seismological methods to study the physics of earthquakes and the tectonic processes that cause them.

“The ideal seismologist would have three talents: (1) a sophisticated understanding of the physics of seismic wave generation and propagation; (2) an uncanny ability to extract information from seismograms (both intuitively and via digital data processing), and (3) the geophysical intuition to use seismograms to both ask and answer questions about how the Earth works. Many fine seismologists have one of these talents, a select few have two, and Hiroo excels at all three.

“Hiroo’s research career began in the early sixties at Tokyo University, where he helped develop a seagoing gravimeter and worked on high-pressure mineral physics experiments. He began work in seismology in the late sixties, by which time the formulation of plate tectonics showed how valuable seismological data could be in tectonic studies. At that time, however, techniques existed to exploit only a small fraction of the information in seismograms. In particular, only the times of first-arriving seismic waves and their polarities were used to infer the location and fault geometry of earthquakes. As a result, seismologists could study only the initial rupture of large and complex earthquakes and were seriously hampered by the comparative sparseness of seismic stations, including their restriction to on-land sites.

“In the past 20 years, however, this situation has changed dramatically as a result of pioneering studies by Kanamori and others. One of the key elements came from advances in the theory of the Earth’s normal modes, which can compute the entire displacement field generated by an earthquake. One of the most successful approaches, introduced by Kanamori in 1970, used mode theory to study earthquake sources utilizing seismograms recorded at different azimuths from the earthquakes. In short order, first in Japan and then after he came to Caltech, Hiroo studied the major subduction zone earthquakes.

These included the gigantic 1960 Chilean earthquake, which he estimated had an average slip of 21 m on a 800 by 200 km fault. He not only used the seismic data from the world-wide Standard Seismograph Network, which were then state of the art, but also developed methods to analyze older data from important earthquakes, including the great 1923 Tokyo earthquake.

“His series of papers based on these studies led to much of our current picture of how the largest earthquakes reflect the release of strain built up at the locked interface between the subducting and overriding plates. Kanamori also showed that some large earthquakes indicate internal failure of the subducting slab under its own weight.

“He went on to propose that there were systematic differences between subduction zones in the fraction of the total plate motion that occurred as seismic slip and that these differences reflected fundamental differences in the nature of the plate interface that were also manifested in the pattern of volcanism and subduction zone morphology.

“Hiroo has also been one of the leaders in elucidating the physics of earthquakes. His work clarified the relationship between the measured seismic moment and the minimum energy released by earthquakes and established the `moment magnitude’ scale, which provides a consistent way of characterizing the size of earthquakes from small to large, while maintaining continuity with the work of Richter and Gutenberg.

“Another important thrust of his work has been developing methods to use seismograms to study the details of earthquake rupture. Hiroo has been one of the leaders in showing how during earthquakes the amount of slip varies significantly in space and time along faults. These results, some of which can now be confirmed by high-resolution geodesy, provide the `ground truth’ for attempts to use the results of laboratory studies and theories of fracture to understand how earthquakes actually start and work.

“These are a few highlights of his accomplishments: time prohibits me from saying much more. I do not have time to discuss many others, including development of a sophisticated new seismic network in southern California, contributions to understanding California earthquakes and tectonics, and efforts to understand and reduce earthquake hazards. Similarly, I can only briefly note his overall impact on seismology and geophysics, via his publications, his professional service, and his interactions with others. I vividly recall many late night sessions with him when I was in graduate school, discussing both specific research questions and more general geophysical issues.

It seemed as though Hiroo knew just about everything about earthquakes and seismology and a lot about almost any topic in geophysics. The opportunity to exchange ideas and learn was invaluable. My experience is surprisingly common: both in Japan and in the United States, an enormous number of us have been influenced by Hiroo as students, coworkers, colleagues, and students of his students.

“His skill, and insight, and his willingness to share them have done much to shape geophysics. We are very fortunate to have him.”

—SETH STEIN, Northwestern University, Evanston, Ill.

Response

“Thank you, Bill. I was surprised when I opened the letter from AGU. I was even more surprised when I read on and found that the Bucher Medal is for the study of the Earth’s crust. I have not viewed myself as a crustal scientist. I believe that AGU is recognizing the importance of an integrated approach to crustal and global tectonic studies, rather than my actual contributions. I have had the good fortune to collaborate with many others and would have accomplished little without constant interaction. I cannot thank everyone in 3 minutes so I will describe how others have helped shape my view of the crust.

“Thank you, Seth, for your very kind words.

“When I heard that I would receive the Walter H. Bucher medal, I was certain that the AGU had mixed up the names. I know that there are many people who would deserve this medal much more than I do. However, after it was confirmed that the letter was correctly addressed, I decided that it is not necessarily given to me as an individual, but is given to the type of science I do; I am grateful to the American Geophysical Union for this.

“I realize that I am not very effective in organizing, promoting, and managing big science programs. I like to solve some of the mysteries that nature presents to us using whatever tools I can manage to use. I have many fond memories of pondering over some curious problems, coming up with some rough ideas, and finally solving them to my satisfaction. I was fascinated by spectacular long-period waves from giant earthquakes, slow earthquakes, world-circling seismic waves caused by the Mt. St. Helens eruption, atmospheric oscillations excited by the Pinatubo eruption, strange seismic signals during the passage of a space shuttle over Los Angeles, etc. Unfortunately, my ability is limited, so I needed lots of help from my colleagues, associates, and students through hours and hours of discussions.

“I would like to thank the late Hewitt Dix, who gave me an opportunity to work at the California Institute of Technology as a “freelance” postdoctoral fellow in 1965. The old Seismological Lab in a mansion on San Rafael Hill in Pasadena had a special atmosphere. During my postdoc years, I was lucky to have a small desk set up for me at a corner of a large conference room where I could talk to many graduate students, like Lane Johnson, Leon Teng, and Francis Wu, and to all the distinguished visitors and seminar speakers passing by my desk every day. I benefited from numerous coffee break discussions in the basement among a complex array of heating pipes and telephone switches. Don Anderson, Clarence Allen, Stewart Smith, Jim Brune, and Charles Richter were among the frequent participants. Numerous conversations with them, including some monologues from Charles Richter, helped me prepare myself for becoming a professional seismologist.

“When I came to Caltech in 1972, with the encouragement from Bob Sharp, Gene Shoemaker, and Don Anderson, the Seismological Lab converted a bathroom attached to the former Hugo Benioff’s office into my new office. For several months thereafter, I took advantage of the wisdom of the many visitors who inadvertently rushed into my office. Many of these inevitably hasty interactions turned out to be key to solving many mysterious problems later. I feel that the type of interactions I had during those days in the cluttered Lab had a profound influence on shaping my career. This good tradition was kept up in the present Seismological Lab, and I have opportunities to learn from even more people, including colleagues, students, and visitors; many of them are sitting in this room.

“I was very excited when I thought that I finally understood what nature is telling me. Then some of my colleagues told me that someone else had already discovered it. In some cases someone, very often one of my students, later disproved my conclusion. Despite these unfortunate events, I have been very lucky to work with good colleagues, students, and staff, both in Japan and the United States. I regret that the names are too numerous to mention here, but I sincerely thank all the people who shared with me the excitement of finding the secret of nature.

“Unfortunately, it is getting more and more difficult to get support for this type of science. I believe many of my colleagues feel the same way and are struggling to get support for their research. In this regard, I especially thank the American Geophysical Union for recognizing the importance of intellectual endeavor in promoting science for the future.

“Finally, the experience of the last few years working with Egill Hauksson, Tom Heaton, Rob Clayton, Jim Mori, Lucy Jones, and many other people at Caltech and the U.S. Geological Survey to promote real-time seismology has been very exciting. It is truly gratifying to me to see how the result of our science is being used effectively for the safety and welfare of the public.”

—HIROO KANAMORI, California Institute of Technology, Pasadena, Calif.