U.S. Geological Survey, Menlo Park, Calif.
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.
“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.
“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.