Frequency dependence of the visibility and depths of mantle seismic discontinuities

George Helffrich*, Craig R. Bina

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

52 Scopus citations

Abstract

The visibility and apparent position of a seismic gradient zone depends on the seismic wave frequency at which it is observed, which we illustrate by showing how the visibility and depth of the olivine α→β phase transformation (410 km discontinuity) change as temperature varies. Temperature variations change bottomside reflection coefficients by factors of 2–4 in the 0.5–1.0 Hz frequency band, which can explain spatial variability in short period P′ 410P′ observations and the small apparent variability in observed 410 km discontinuity depths. Discontinuity depths inferred from the time lags of these reflections are also frequency dependent, leading to a frequency dependence of estimates of mantle lateral thermal variability based on discontinuity displacements. The frequency dependent seismic Clapeyron slopes for the olivine α→β phase change we compute are 2.04 MPa K−1 at 0.2 Hz and 2.12 MPa K−1 at 0.05 Hz, and differ significantly from thermodynamic slope for the Mg2SiO4 end‐member.

Original languageEnglish (US)
Pages (from-to)2613-2616
Number of pages4
JournalGeophysical Research Letters
Volume21
Issue number24
DOIs
StatePublished - Dec 1 1994

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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