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We derive a new map of global topography on the 410‐km discontinuity from observations of precursors to PP obtained by stacking almost 25,000 long‐period seismograms. The inferred ‘410’ topography exhibits average peak‐to‐peak amplitude of about 30 km, has a strong degree‐one component, and is highly correlated with previous results obtained from SS precursors [Flanagan and Shearer, 1998]. Spatial variations in ‘410’ topography appear unrelated to ocean‐continent differences, suggesting that continental roots are not a significant factor in observed global temperature variations at 410 km depth.
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Flanagan et al. (1999) studied this question.
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