Correlation between the shear-speed structure and thickness of the mantle transition zone

Details Correlation between the shear-speed structure and thickness of the mantle transition zone Correlation between the shear-speed structure and thickness of the mantle transition zone

Apr 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003pepi..136...25l&link_type=abstract

Physics of the Earth and Planetary Interiors, Volume 136, Issue 1-2, p. 25-40.

Physics

11

Scientific paper

The 410 and 660km seismic discontinuities that bound the mantle transition zone (TZ) are attributed to phase transformations in olivine structure. This implies that variations in TZ thickness (HTZ) should correlate with those in TZ temperature. Pertinent seismic evidence has so far been ambiguous, however. We measure converted-wave (/Pds) differential times tdiff=tP660s-tP410s in SE Asia and Australia and compare them with /S-velocity (βTZ) estimates from regional tomographic models. Both tdiff and βTZ vary on a scale of a few hundred kilometers. Inferred variations in HTZ are up to /+/-30km over length scales larger than 500km, implying /+/-200K thermal heterogeneity if the effect of composition can be neglected. tdiff and βTZ correlate strongly; the linear dependence of HTZ on the average temperature within the TZ is consistent with olivine Clapeyron slopes. We also show that this relationship holds on a global-scale as well, provided that the scalelengths and uncertainties of the variations in tdiff and βTZ are taken into account. These results confirm that the transformations in olivine structure give rise to the 410 and 660km discontinuities globally.

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