CAREER: Environmental Seismology and Geomechanics

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There are many Earth processes besides earthquakes that cause ground movement. In particular, turbulent river motions, and sediment transported by these motions, sea ice-ocean wave interactions, subglacial water flow, and hydrothermal activity all cause ground motion that can be observed with sensitive seismic instrumentation. This project makes use of such unique seismic observations to quantitatively better understand these Earth processes, many of which are extremely complex and poorly observed yet important both geophysically and societally. These processes also share similar basic mechanics involving the interactions of fluids with solids, and this project will result in new insights into how fluid and solid mechanics combine in nature to produce the diverse phenomena described. This interdisciplinary work helps improve flood warnings, sea ice predictions, sea level rise predictions, and an understanding of induced earthquakes.The primary goal of the project is to improve our ability to make use of seismic observations of environmental sources other than earthquakes. Improvements in applying wave propagation tools in complex environments and improvements in the interdisciplinary mechanics that governs how these sources couple seismically are the main avenues by which this goal will be attained. The new mechanics focused on here involves a better-integrated understanding of fluid-solid interactions and how these interactions combine to produce seismically observable ground motions. This is accomplished partly by analytic approximations to couple forces from turbulent eddies with nearby solids. Further semi-analytic approximations are used for wave propagation in complex media. With the primary goals accomplished, the new observations will help constrain aspects of the mechanics of these complex systems that have been difficult to observe with other techniques. This is anticipated to lead to new conceptual ideas about these systems that in turn are expected to lead to new quantitative understanding of the geophysical processes underlying the observed phenomena.