CAREER: The role of spatial scale in continental tectonics

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This CAREER project is designed to test how the apparent constituitive relation of continental materials varies as a function of spatial scale. It is motivated by a longstanding debate over interpretations of surface deformation. At small scales, on the order of tens of kilometers, individual faults are usually represented as dislocations in elastic half spaces; at large scales, on the order of thousands of kilometers, deforming volumes are usually represented as thin viscous sheets. Of course, the real response of the Earth to tectonic stresses over all scales must be self-consistent, suggesting some phase transition or composite behavior must occur at intermediate length scales between these extremes. The investigator will use a combination of observations of surface strain and numerical simulations to search for and characterize transitional responses. The observations will include GPS, radar interferometry, topographic analyses, and syntheses of seismic and paleoseismic data for test regions in the Northwest U.S. and the greater San Andreas system. In addition, she will develop new educational materials directed toward building a general understanding of scaling, numeracy, and basic scientific literacy for young citizens, especially nonscientists. Some of these materials will be based directly on the proposed research, others on applications of scaling and numeracy to everyday life.As humans, we view the solid earth as just that: solid, immutable, and unchanging, at least under normal circumstances. However, this perspective depends on the shortness of human lives and the limited range of our vision. In fact, over a range of time and spatial scales much greater than our usual perception, the solid earth has a very complicated and dynamic response to the vast forces of tectonics. If we lived for millions of years, or could see the whole planet at once, we would detect a range of processes that appear to vary depending on our focus. Some are more evident at shorter spatial and time scales, others at longer ones. This research explores how scaling, especially in space, affects the effective material properties of the Earth, especially how it responds to tectonic forces. A better understanding of scale dependence might help us to understand how the properties of the Earth vary with depth, whether the ancient history of continents affects the current landscape, and even why earthquakes and mountain ranges occur in some places and not others. Scaling is not just important in tectonics. It also plays a role in our everyday lives, from the size of the budget deficit to energy efficiency to food security. This experiment also includes the development of new materials to teach young citizens how to use numbers and physical concepts to make good decisions and better understand the complicated science-based issues of our time.