Dr. David Shelly, a research seismologist with the U.S. Geological Survey, was named one of President Obama's recipients of the Presidential Early Career Award for Scientists and Engineers, the highest honor bestowed by the United States government on science and engineering professionals in the early stages of their independent research careers.
Shelly pioneered ways to detect tectonic tremor, or a bunch of tiny earthquakes strung together, occurring deep within the Earth's crust, below the depth of where damaging earthquakes have occurred in the past and are likely to occur in the future. By precisely locating these clusters of earthquakes, Shelly was the first to determine that they originated on the down-dip extensions of the faults, and are caused by slip on faults rather than the migration of fluids. The previous reigning hypothesis had been that these portions of the faults had moved entirely by the migration of fluids. This information is important in identifying and determining the risk due to hazards like earthquakes and volcanoes and finding ways to build more resilient communities.
"It is inspiring to see the innovative work being done by these scientists and engineers as they ramp up their careers—careers that I know will be not only personally rewarding but also invaluable to the Nation," President Obama said in a Sept. 26 news release. "That so many of them are also devoting time to mentoring and other forms of community service speaks volumes about their potential for leadership, not only as scientists but as model citizens."
The Presidential early career awards embody the high priority the Obama Administration places on producing outstanding scientists and engineers to advance the Nation's goals, tackle grand challenges, and contribute to the American economy.
"This is a big honor and quite a surprise," said Shelly. "It is gratifying to see that the science I have worked on—work that I find interesting—has been recognized by others as significant."
"Dr. Shelly's work lies on the critical frontier of understanding that transition zone between where Earth releases accumulated stress through infrequent, catastrophic large earthquakes versus continuous, slow creep," said USGS Director Marcia McNutt. "His work will lead to insights on reducing hazards from one of the deadliest form of natural hazards. Furthermore, Dr. Shelly also provides leadership in the field of tectonic tremor by developing and fostering international collaboration, particularly between researchers in the United States and Japan."
When tectonic tremor was first discovered a decade ago in Japan's subduction zones—or places where one tectonic plate moves under another tectonic plate—its source was unknown. Shelly was the first to establish that tectonic tremor occurs on the subduction zone plate boundary, the deep extension of the fault where damaging earthquakes occur. When tectonic tremor was found in California, Shelly was the first to demonstrate that there, too, the tremor occurs as multiple events on the downward continuation of the dangerous faults.
"What I have done is to develop techniques to analyze what is happening deep within the earth in the way we analyze typical earthquakes that occur closer to the earth's surface," said Shelly. "That involves taking a long-time period of data—10 years of continuous records of ground motion—and I used that information to analyze the seismic signals and identify that small earthquakes were occurring deep within the earth causing this 'noise' versus what was originally thought of as fluid movement."
Shelly was also the first to document many curious behaviors of tectonic tremor, including migration along the fault, strongly periodic recurrence, and changes in tremor patterns related to nearby earthquakes.
"There are ways the tremor activity could relate to bigger earthquakes and impact society," said Shelly. "When you have slip on the deeper parts of a fault, you add stress to the more shallow parts. Scientists are still trying to understand the relationship between tectonic tremor and bigger earthquakes on adjacent parts of a fault.”
What makes this research possible are several things, according to Shelly, such as high quality seismic networks, the ability to store continuous seismic data that was technologically impossible in the near past, and computers fast enough to process large quantity of data for analysis.
"As recently as a decade ago, people imagined that faults ended at where the earthquakes ended," said Shelly. "But with the discovery of these small earthquakes at least 15 miles below the earth’s crust—where damaging earthquakes occur about 5-7 miles beneath the earth's crust—we showed that faults can continue through the entire crust. And by studying tremor, we can see that deformation on the deep fault occurs with complicated patterns that we had no idea existed in the past. There is hope that this research will give insight into bigger earthquakes that will eventually be critical information to help build more resilient communities."
Shelly is now applying his seismology expertise to studying the deep-rooted volcanic system of the Long Valley Caldera, which may lead to insights into the future hazards posed by this system, and may help identify magma movements in the build-up to an eruption.
"Volcanoes form and evolve from the interaction of many processes," said Shelly. "There are interesting and unusual earthquakes associated with volcanoes that can give insight into these processes. Some of the techniques I have developed with regard to tectonic tremor may be able to help us better understand and monitor volcanic activity."
Shelly joined USGS in 2008 as a Mendenhall Postdoctoral Fellow with the Earthquake Hazards Team in Menlo Park, Calif., after spending a year as a Miller Postdoctoral Fellow at the University of California, Berkeley, Department of Earth and Planetary Sciences. He graduated from Stanford University with a PhD in Geophysics in 2007; Whitman College with a B.A. in Mathematics-Physics, Summa Cum Laude, in 2000; and spent several months at Otago University in New Zealand in late 1998, studying physics and geology as part of a semester abroad. In 2011, Shelly received the Charles F. Richter Early Career Award from the Seismological Society of America; in 2010 an editor's Citation for Excellence in Refereeing, Geophysical Research Letters; was the first recipient of the Keiiti Aki Young Seismologist Award from the American Geophysical Union in 2008, given to recognize the scientific accomplishments of a junior scientist who makes outstanding contributions to the advancement of seismology.
"I have certainly gotten a lot of help along the way," said Shelly. "My father was my high school physics teacher. From there, I have had a lot of help and good mentors—and I wouldn’t be here without them. I would particularly like to thank our Japanese partners for sharing ideas, data and collaboration that we have had in the past and look forward to in the future."
The Presidential Early Career Awards for Scientists and Engineers was established by President Clinton in 1996, and are coordinated by the Office of Science and Technology Policy within the Executive Office of the President. Awardees are selected for their pursuit of innovative research at the frontiers of science and technology and their commitment to community service as demonstrated through scientific leadership, public education, or community outreach. Shelly was one of 94 recipients this year.