Abstract:

Stacks of global seismic data reveal the time and distance dependence of high-frequency (1-Hz) precursors to the seismic phase PKKP Synthetic seismogram modeling shows scattering from random, small-scale topography at the PKKP core-mantle-boundary 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 m and correlation length of 7 to 10 km 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.