Tonga and Fiji Seismic Arrays for Investigating Slab Processes and Upper Mantle Phase Transformations

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Abstract for proposal EAR0001158 (PH #51x; Spring 2000 Panel)Title: Tonga and Fiji Seismic Arrays for Investigating Slab Processes and Upper Mantle Phase TransformationsPI's: Douglas A. Wiens and Gideon Smith, Washington UniversityThe detailed structure of the Tonga subduction zone is being studied with seismic data from two dense seismic arrays. The arrays are to be deployed for about a year, one within the active island arc (Tonga), the other in the backarc environment (Fiji). Data from the arrays is used to characterize and model seismic wave propagation effects within the subducting oceanic plate and the adjacent mantle. These wave propagation effects result from interactions with seismic velocity discontinuities in and near the subducting plate. The depths, velocity contrasts, and sharpness of the velocity discontinuities will be used to help better understand the temperature, mineralogy and presence of water in the subducting slab and the surrounding mantle at greater spatial detail than is possible from data recorded teleseismically. Dense array data also allows higher precision studies of the mechanics of deep earthquakes.