Thomas C. Hanks, Research Geophysicist at the Menlo Park, CA office of the U.S. Geological Survey, was selected as the 2011 Joyner Lecturer. He delivered his lecture at the SSA April 2011 Annual Meeting in Memphis, TN. Hanks? research has ranged widely across the causes and effects of earthquakes, including studies of earthquake source parameters and magnitude scales, earthquake ground motion, the morphological evolution of fault scarps, and seismic hazard analysis. For the past five years, he has led, with previous Joyner Lecturer Norm Abrahamson, the Extreme Ground Motion Research Program, a five-year study of the origin, nature, and plausibility of extreme ground motions at Yucca Mountain. Extreme ground motions refer to the extremely large earthquake ground motions that can occur at extremely low probabilities of exceedance and was the subject of his Joyner Lecture.