Observations of PKKP Precursors Used to Estimate Small-Scale Topography on the Core-Mantle Boundary

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Science  01 Aug 1997:
Vol. 277, Issue 5326, pp. 667-670
DOI: 10.1126/science.277.5326.667

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Stacks of global seismic data reveal the time and distance dependence of high-frequency (1-hertz) precursors to the seismic phasePKKP. Synthetic seismogram modeling shows that scattering from random small-scale topography at the PKKPcore-mantleboundary reflection point generates precursory arrivals similar to those seen in the data. Models with a root mean square core-mantle–boundary topography of 250 to 350 meters and correlation length of 7 to 10 kilometers explain the main features of the data. However, a systematic range-dependent misfit between observed and predicted precursor power suggests that inner core scattering may contribute to the precursors.

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