Roland Burgmann on the Search for How Earthquakes Really Work

Interview for the Special Topic of Earthquakes, October 2010

Roland BurgmannIn our Special Topics analysis of earthquakes research over the past decade, the work of Dr. Roland Burgmann ranks at #1 by total cites and #2 by total papers, based on 74 papers cited a total of 1,539 times. Two of these papers rank on the list of the 20 most-cited papers in the Topic over the past decade as well.

Burgmann's record in Essential Science IndicatorsSM from Clarivate Analytics includes 82 papers, the majority of which are classified under Geosciences, cited a total of 1,981 times between January 1, 2000 and June 30, 2010. He is Professor and Chair of the Department of Earth and Planetary Science at the University of California, Berkeley.

Below, he talks with about his highly cited earthquakes research.

SW: Please tell us about your educational background and early research experiences.

I greatly benefitted from the training and exposure to research across a wide range of geological and geophysical areas. I started my Geology studies in Germany, in 1985. Back then my interests were mostly in Geochemistry and Petrology, but also in Structural Geology. In 1987 I came to the University of Colorado in Boulder as a Fulbright exchange student, where I had the fortune to get involved in research on San Andreas fault deformation with my M.S. thesis advisor, Roger Bilham.

I arrived at Stanford for my Ph.D. studies in the summer of 1989 to work in fault mechanics, and was soon shaken up by the October 17 Loma Prieta earthquake. The event not only forced us to abandon the building the Geological Sciences department was housed in, but also greatly increased my interest in earthquake-related topics.

At Stanford, I had the fortune to work with both David Pollard and Paul Segall on a rather broad range of topics related to fault structure and crustal deformation over a wide range of spatial and temporal scales. My ongoing Active Tectonics research is very much a reflection and continuation of the diverse interests I developed during that time.

SW: What first drew your interest to earthquakes?

UC Berkeley student Eileen Evans centers and levels a tripod for a GPS antenna, while postdoc Gareth Funning readies the receiver to collect data for measuring active crustal deformation near the Calaveras fault in the San Francisco Bay Area, California. Photo taken by Isabelle Ryder..

Even before the Loma Prieta earthquake, it was probably a field visit and workshop following the 1987 Superstition Hills earthquake and a later San Andreas fault field trip with Roger Bilham and Kerry Sieh from Caltech that put me firmly in the earthquake research camp.

SW: Your most-cited paper in our analysis is the 2000 Science paper written with several coauthors, "Coseismic and postseismic fault slip for the 17 August 1999, M=7.5, Izmit, Turkey earthquake." Please tell us about your methods and findings in this work.

This paper and a number of subsequent ones arose from a well-timed sabbatical visit at MIT just when the Izmit earthquake and subsequent Düzce event occurred. Rob Reilinger, Semih Ergintav, and colleagues had carried out GPS studies in the region for many years, providing well-established pre-earthquake deformation rates and allowing for the collection of an amazing geodetic data set soon after the earthquake.

My experience with modeling fault deformation allowed us to explore the newly collected data, more or less in real time. Liz Hearn and Kurt Feigl also happened to be spending time at MIT around then, making for a perfect combination of data and expertise that we could apply to our studies of the coseismic and postseismic deformation associated with these important earthquakes.

Starting with a simple model based on offsets of just a couple of GPS stations, we soon were able to develop a detailed model of the rupture kinematics using both GPS and InSAR data. Maybe most interesting were the rapid post-earthquake deformation transients from deep-seated afterslip that likely helped trigger the Düzce earthquake, three months later. This represents one of the best examples of the importance of postseismic relaxation processes in the triggering of earthquakes.

SW: Based on your paper list, your work takes you all over the world—Turkey, Hawaii, Sumatra, India, Alaska, etc. Is there a particular seismic phenomenon or motif that unites this far-flung research?

The connecting theme is to improve our understanding of the fundamental nature of the earthquake cycle and mechanics of crustal deformation. Studying earthquakes of varying styles and sizes and in different tectonic environments turns out to be extremely valuable in that context. Of course, it is also true that plate boundary zones and deformation events in different parts of the world are simply fascinating and unique in and by themselves, and if opportunities arise to get involved in research there, I am eager to take them.

SW: Earlier this year, you and two coauthors published a paper in the Bulletin of the Seismological Society of America, "Triggering effect of M 4-5 earthquakes on the earthquake cycle of repeating events at Parkfield, California." Would you tell us about the research behind this paper?

One problem with trying to better understand why earthquakes happen when and where they do is that our observational record of large earthquakes is simply too small, even if we try to study them globally. This work with former postdoc Kate Chen, who is now on the faculty at National Taiwan Normal University, and Bob Nadeau at the Berkeley Seismolab, aims to use earthquake cycles of very small earthquake ruptures to better understand the process of fault interaction and earthquake triggering.

"...plate boundary zones and deformation events in different parts of the world are simply fascinating..."

In this particular study we are trying to understand to what degree the timing of small repeating microearthquakes (with magnitudes of less than M=2) is influenced by the occurrence of nearby moderate events (M=4-5) along the Parkfield segment of the San Andreas fault. As the recurrence intervals of these small events are on the order of months to a few years and there are dozens of them, this allows us to get a much more quantitative view of such interactions.

Kate, Bob, and I are continuing to do more research along this theme, and even though there are aspects of these small events that are quite different from much larger earthquakes, this is a great model system to fully explore.

SW: Lately, there has been speculation in the popular press about the increase (or perceived increase) in earthquake activity worldwide in the past year. Does this concern have any basis or validity?

No, at least not yet. Statistically, the recent rate of occurrence of large earthquakes is not out of the range of that observed in previous years over the historic record (there is a nice summary on that in a release by Mike Blanpied at the USGS.

What is notable, though, is how many of these events occurred in populated areas and thus caused harm to people. As the human population continues to grow, and appears to grow most rapidly in earthquake-prone areas, we are likely to see more disastrous events such as the recent ones in Haiti, Chile, and China.

SW: How much have we learned about earthquakes in the past decade? What advances would you like to see in the future of earthquake research?

There are probably more new questions that were raised in the last decade than we found answers to old ones. We have learned to better understand the occurrence of earthquakes in the context of crustal deformation and the mechanics of the earthquake cycle, which should continue to lead to improved forecasting of earthquake hazard. We still can't predict earthquakes (lacking reliable precursory signals), but continue to better understand why that is so.

Thanks to much-improved seismic and space geodetic measurements, we are now finding completely new types of fault slip events (such as non-volcanic tremor, low frequency earthquakes and various types of aseismic slow slip events) with fascinating properties that we are just beginning to understand. There is much left to do to really figure out how earthquakes and fault slip really work.End

Roland Burgmann, Ph.D.
Department of Earth and Planetary Science
University of California, Berkeley
Berkeley, CA, USA


Zhang PZ, et al., "Continuous deformation of the Tibetan Plateau from global positional system data," Geology 32(9): 809-12, September 2004 with 177 cites. Source: Essential Science Indicators from Thomson Reuters .



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