David Richard Shelly was awarded the 2012 James B. Macelwane Medal at the AGU Fall Meeting Honors Ceremony, held on 5 December 2012 in San Francisco, Calif. The medal is for “significant contributions to the geophysical sciences by an outstanding young scientist.”
David R. Shelly is awarded the 2012 Macelwane Medal for his revolutionary advances in understanding the nature of tectonic tremor and its role in the earthquake preparation process. His innovations in the study of this subtle “noise” from deep within the Earth has opened a new window into the processes governing the earthquake cycle on major plate boundary faults and the magmatic systems beneath active volcanoes.
Tectonic (aka “non-volcanic”) tremor was initially recognized as an enigmatic seismic signal associated with subduction beneath Japan. David’s innovative use of cross-correlation techniques on continuous waveform data enabled him to discover that tremor consists of many, overlapping low-frequency earthquakes (LFEs) on the subduction interface, rather than being generated by fluid dynamic processes as many had speculated. David discovered migration patterns within the tremor associated with geodetically detected slow-slip events (together known as episodic tremor and slip or ETS), providing a means of tracking the spatial progress of individual slow-slip patches comprising an ETS event.
Turning his attention to the San Andreas Fault in central California, David showed that the tremor is confined to a long, ribbon-like band in the lower crust directly beneath the seismogenic fault and that, as in subduction zones, the tremor consists of many superimposed shear-slip events. This provided the first clear evidence that the central section of the San Andreas Fault extends entirely through the crust as a vertical, strike-slip fault rather than terminating in a lateral decollement at midcrustal depths as many had proposed. David identified a wide range of tremor migration patterns, including asystematic migration away from the eventual epicenter of the 2004 magnitude 6 Parkfield earthquake, which, analogous to subduction zones, may indicate a precursory slow-slip event at depth. David discovered patches of repeating LFEs that display an intriguing array of temporal patterns ranging from periodic to period-doubling to chaotic suggesting that small changes in conditions can produce dramatic changes in behavior as is characteristic of complex systems. He has recently expanded his research to include volcanic seismicity and tremor in major volcanic systems.
Awards recognizing David’s contributions include the AGU Keiiti Aki Young Seismologist Award, the Presidential Early Career Award for Scientists and Engineers, and the Seismological Society of America’s Charles H. Richter Early Career medal. These many accomplishments and accolades have not altered David’s modest, unassuming demeanor. He is a delightful colleague and valued collaborator with a balanced approach to science and life.
–Jeanne Hardbeck, U.S. Geological Survey, Menlo Park, California; and David Hill, U.S. Geological Survey, Menlo Park, California
Thank you, Dave and Jeanne for the nomination and citation, as well as for being enthusiastic collaborators and mentors over the past few years.
This is a tremendous and unexpected honor for me. I consider myself extremely fortunate to have had such positive influences in all aspects of my life, from family and friends to mentors and collaborators over the years. On the personal side, I especially thank my parents fostering a curiosity of the natural world, and my wife Liz for her patience and encouragement.
I have been equally fortunate in my education and early career with the support of many generous mentors and colleagues. I thank Mark Beck for introducing me to research (in physics) during my undergraduate education at Whitman College. My PhD advisor, Greg Beroza, was then willing to take a chance on a student with little prior experience in geophysics, and he provided a potent combination of enthusiasm and insight into earthquake processes. I learned a lot from him and from fellow graduate students at Stanford, as well as from mentors since then such as Satoshi Ide, Roland Bürgmann, Bill Ellsworth, Dave, Jeanne, and many others. Now, as a seismologist at the USGS, I still feel a bit like a kid in a candy shop with so many brilliant and accomplished earthquake and volcano scientists who don’t seem to mind being pestered with questions. I am very grateful to be working in such a stimulating and supportive environment.
I am also grateful for the investments the seismological community has made in shared and open data. The research that collaborators and I have done, which is cited here, has relied heavily on these investments. We are very fortunate to be in an age where data centers provide free and open access to terabytes upon terabytes of high quality seismic data, and it has enabled scientific progress that wouldn’t have been possible otherwise. By being able to access nearly all of the data, rather than just that collected by a single group, it’s a case of the whole being greater than the sum of the parts. I know many people worked very hard to set up this infrastructure, and many people continue to work hard to maintain it. I would like to thank all of the people and organizations that have worked to collect and archive data, as well as the agencies that support these efforts. I think this openness and investment in shared resources is a major strength of the seismological community.
So, I consider myself extremely fortunate to be in a profession where I’m working with brilliant people, studying amazing data, and attempting to answer fascinating questions related to the inner workings of our planet.
–David Shelly, USGS, Menlo Park, California