Low-Frequency Attenuation in Polycrystalline Silicates and Silicate Partial Melts

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Reid F. Cooper, Principal InvestigatorUniversity of Wisconsin-Madison The measurement of the low-frequency attenuation behavior of polycrystalline olivine aggregates, of olivine-orthopyroxene aggregates and of olivine-based partial melts will be pursued. Specifically, the polycrystalline materials, which will have carefully engineered microstructures, will be subjected to dynamic ("sub-resonant", oscillatory loading) and quasistatic (constant loading, i.e., creep) so as to evaluate the attenuation behavior as functions of (i) temperature (1150 to 1350 degC), (ii) frequency (2x10e-4 to 1 Hz), (iii) phase volume fraction and morphology (phase percolation and phase separation/layering in the solid state; melt segregation beyond the grain scale in partial melts), and (iv) dislocation-creep sub-microstructure. The study/characterization of microstructural effects (engineered into these specimens so as to mimic deformation-induced microstructures) on seismic-frequency absorption is one key to applying seismic data to infer deformation behavior in active tectonic terranes.