CSEDI: Collaborative Research: Observational and Theoretical Constraints on the Structure and Rotation of the Inner Core

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The major goals of this collaborative project are two-fold: (1) To obtain high resolution images of inner core anisotropy, through a proposed PASSCAL experiment; (2) To develop a geodynamic model for the origin of the observed seismic anisotropy. The investigators plan to deploy two linear arrays of 15 new stations in the interior of Alaska, coded as Alaska Receiving Cross-Transects for the Inner Core (ARCTIC). New data from earthquakes in South Sandwich Islands to the arrays will provide critically needed lateral and depth samples of the inner core for determining the inner core rotation and for resolving the structure of the inner core transition zone and the depth-dependence of inner core anisotropy and attenuation. the team plans to develop a geodynamic model for the formation of anisotropy, using the new and existing data as a constraint. The major objective of the modeling is to identify and investigate physical processes, including effects of plastic deformation, inner-core growth and recrystallization, and anisotropy in the thermal conductivity, that can account for the observed depth and lateral variations in anisotropy. The developed model will serve as a physical context for interpreting the seismic observations. Predictions of the model will be used to calculate synthetic waveforms, which are subsequently compared with the observations to refine the model. The new data collected will also be used to elucidate crustal and upper mantle structure of the Alaska interior. The north-south line from Fairbanks to Prudhoe Bay will cross the Brooks Range in northern Alaska, and The east-west line between Fairbanks and Nome will cover parts of western Alaska in a known, but nearly unstudied, region of extensional tectonics.