Premium
The trouble with seeing double
Author(s) -
Flores Claudia,
Lay Thorne
Publication year - 2005
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2005gl024366
Subject(s) - mantle (geology) , post perovskite , phase boundary , geology , waveform , core–mantle boundary , discontinuity (linguistics) , stacking , phase transition , phase (matter) , perovskite (structure) , boundary layer , geophysics , materials science , mineralogy , condensed matter physics , thermodynamics , physics , chemistry , crystallography , nuclear magnetic resonance , mathematical analysis , mathematics , quantum mechanics , voltage
The recently discovered phase transition for (Mg,Fe)SiO 3 from perovskite to post‐perovskite structure for pressure‐temperature conditions in the lowermost mantle provides a plausible mechanism to explain a several percent shear velocity increase detected at the top of the D″ region in many regions. The phase transition has a large positive Clapeyron slope, and given the likely presence of a strong temperature increase just above the core‐mantle boundary, D″ conditions may reintersect the phase boundary, resulting in a thin layer of perovskite below a lens of post‐perovskite, separated by a few percent velocity decrease. Detection of such a velocity decrease is shown to be much harder than detection of the shallower velocity increase due to fundamental properties of seismic waves; purported observations in support of a double‐discontinuity are re‐evaluated based on waveform modeling. Waveform stacking procedures are required for reliable detection of the lower half of any double‐crossing of the phase boundary.