Donald V. Helmberger, Ph.D. and Smits Family Professor of Geophysics Emeritus at Caltech, and one of the most impactful seismologists to have lived, died on 13 August 2020. Don was born 23 January 1938, the youngest child of 13, in the small rural town of Perham, Minnesota. He completed his bachelor’s degree in physics at the University of Minnesota in 1961. That summer, he participated in a cruise involving seismic imaging of the oceanic crust in the Bering Sea and was inspired by the challenge of interpreting the recorded seismic waveforms—the beginning of a lifelong passion. That experience drew him...

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