Profile of Don Helmberger

Beauty may be only skin deep for some, but for Don Helmberger the beauty of the Earth goes all the way to the core. For more than 40 years, Helmberger, Smits Family Professor of Geophysics and Planetary Science at the California Institute of Technology (CalTech; Pasadena, CA), has modeled the beauty of the Earth’s intricate subsurface using seismic wave propagation data to detail its structure and movements. This field of quantitative seismology was unheard of in 1967, when Helmberger was completing his Ph.D. dissertation, designing the first synthetic seismograms from data collected in the Bering Sea. “It was the first modeling experiment, basically,” he says, “and some of my professors wanted to know why I was doing such stuff.”

Seismological modeling is now an integral and expanding part of geophysics research, and it has led Helmberger to many valuable applications, including modeling the characteristics of earthquakes and superplumes (upwelling of the Earth’s mantle), determining the nature of underground detonations, and mapping the transition zones in the Earth’s mantle and core. In his Inaugural Article, published in a recent issue of PNAS (1), Helmberger shed light on one such transitional area in the planet, an ultralow-velocity zone that can be found in pockets above the core–mantle boundary.

Such groundbreaking experiments have helped earn Helmberger many distinctions, including receipt of the first Inge Lehmann Medal from the American Geophysical Union in 1997, the Medal of the Seismological Society of America in 2002, and election to the National Academy of Sciences in 2004. Helmberger remains modest about his contributions in seismology, however. “I’ve really just been taking work that other people have done and doing interesting stuff with that,” he says.