Seth Stein is an extraordinary scientist who has made fundamental contributions to many geophysical disciplines. He has investigated processes within Earth’s lithosphere using techniques including seismology, space-based geodesy and marine geophysics. Seth and his students and colleagues have produced numerous seminal publications in the fields of seismic wave theory, Earth structure, normal mode seismology, plate kinematics, intraplate stresses and seismicity, oceanic microplates, plate boundary deformation, lithospheric heat flow and the structure of ocean plates, the causes of deep earthquakes, paleoplate reconstructions, the growth of the Andes, and seismic hazards. And this list is by no means complete. Seth continues to make major contributions, particularly addressing plate motions and how plate boundaries and plate interiors evolve, with special interest in the resulting earthquakes and hazards. A major focus of Seth’s current research is on better understanding multiple aspects of earthquake hazards, including how, where and when they occur and the shaking that results. Seth and colleagues are exploring how well the hazard maps, which are used to design earthquake-resistant structures and thus reduce losses from earthquakes, represent true seismic hazards, what causes the uncertainties involved and how to make better forecasts. Another focus of Seth’s recent studies involves using seismic imaging methods to identify the processes by which continents rift apart to form new ocean basins, particularly the evolution of North America’s unique 1.1-billion-year-old Midcontinent Rift. Using a novel approach of comparative “riftology,” Seth is discovering how continental rifting starts, how it proceeds and why it ends. As an example, Seth incorporated EarthScope seismic modeling into the construction of a model that resembles the kind of rift initiation occurring in the East African Rift Valleys, solving a long-standing riddle as to why the Midcontinent Rift Zone rifting stopped so soon after it began. This project, as with several others such as the seminal work on modeling the thermal structure of oceanic lithosphere, was done with Seth’s leading collaborator (and also wife and life partner!), the accomplished geophysicist Carol Stein. Seth is also an exemplary mentor, always making sure that students got first-author credit for their work done on big projects, and his enormous enthusiasm and great mentoring skills, combined with his exceptional seismology textbook, which (with its many early open-source preprint versions) has been a defining text for more than 40 years, have brought many students into the field of geophysics.

 

— Michael Wysession Washington University in St. Louis St. Louis, Missouri