Heterogeneity of the lowermost mantle

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210 Scopus citations


Strong heterogeneity at a variety of scale lengths has been imaged in the lowermost mantle using different forward and inverse methods. Coherent patterns in differential travel times of waves that sample the base of the mantle-such as diffracted shear waves (Sdiff) and compressional waves (Pdiff)-are readily apparent, and are compared with results from tomographic studies. Travel time and waveform modeling studies have demonstrated the presence of intense lateral variations in a variety of mapped features, such as a regionally detected high velocity D″ layer, ultra-low velocity zones, D' anisotropy, strong scattering and heterogeneity. Such shortwavelength variations currently preclude confident mapping of D″ structure at smaller scales. Issues of seismic resolution and uncertainties are emphasized here, as well as the limitations of one-dimensional modeling/averaging in highly heterogeneous environments.

Original languageEnglish (US)
Pages (from-to)509-537
Number of pages29
JournalAnnual Review of Earth and Planetary Sciences
StatePublished - Oct 31 2000


  • Core-mantle boundary
  • D″
  • Mantle structure
  • Seismic heterogeneity
  • Ultra-low velocity zone

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science


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