It is an honor to introduce Emily Brodsky, recipient of a 2008 AGU James B. Macelwane Medal. Emily has made creative, diverse, and quantitative contributions to our understanding of the physics of earthquake triggering and rupture processes, hydrological responses to earthquakes, explosive volcanic eruptions, and bubble dynamics. Her research has been provocative and profound, challenging colleagues to rethink basic conceptual models. Her academic career has taken her to great institutions such as Harvard, California Institute of Technology, University of Oregon, University of California, Berkeley, University of California, Los Angeles, and currently University of California, Santa Cruz.
Emily is a bold, seemingly fearless scientist willing to tackle tough problems. She takes on major challenges such as determining “what causes earthquakes” with a broadly based approach that cannot be pigeon-holed into any one discipline. She has established an internationally recognized program on the physics of earthquakes and volcanic eruptions, with current emphasis on the processes by which earthquakes initiate and propagate. With strengths in physics and fluid mechanics, expertise in seismological data collection and analysis, and a keen eye for diverse field observations, Emily couples different geological and geophysical processes and analyzes them quantitatively.
Working at the forefront of research on remote triggering of earthquakes and volcanoes by passage of seismic waves from a large event, Emily has obtained part of an answer to the question above: “Earthquakes cause earthquakes.” In other words, the dynamic stress waves from one event can initiate failure of other events. Investigations of this phenomenon have led her to explain groundwater pressure changes caused by shaking from a remote earthquake as the result of flushing of particulate barriers in fractures induced by the pumping action of the seismic vibrations, allowing pore water pressures to change and thereby to trigger earthquakes. Related studies have led to an innovative determination of the evolution of permeability over time based on her observation that earthquake occurrence appears to affect the phase lag between Earth tides and well-pressure changes due to shaking-induced increase in rock permeability.
Emily is among the few to confront the widely held notion that static stress changes are the predominant control on earthquake interactions and triggering. Rigorous assessment of predictions for the static stress model has been pursued, without finding observational support for the attendant prediction of stress shadows. Emily and colleagues argue that the spatial distribution of aftershocks as a function of distance from a main shock varies in proportion to how dynamic stresses decay, rather than how static stresses diminish. These advances raise questions about when an earthquake is better viewed as a foreshock or an aftershock. She is ever willing to go into the field, to participate in deep fault drilling, and to walk the shatter zones of fault outcrops, seeking insights and measurements that help to understand what causes earthquakes.
On the basis of her broad interdisciplinary contributions to our understanding of faulting processes, volcanic eruptions, and hydrologic influences on deformation, Emily Brodsky immediately brings credit to the American Geophysical Union’s Macelwane Medal and will continue to do so long into her future career.
—THORNE LAY, University of California, Santa Cruz
