Mathematics – Logic
Scientific paper
Jun 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009e%26psl.284...65d&link_type=abstract
Earth and Planetary Science Letters, Volume 284, Issue 1-2, p. 65-75.
Mathematics
Logic
12
Scientific paper
We present a comparison of seismologically observed shear velocity and attenuation on a global scale. These observations are also compared with laboratory measurements of the same quantities made on fine-grained olivine and extrapolated to upper-mantle conditions. The analysis is motivated by recent developments in global attenuation tomography and in laboratory measurements of velocity and attenuation at seismic frequencies and upper-mantle temperatures. The new attenuation model QRFSI12 is found to be strongly anti-correlated with global velocity models throughout the upper mantle, and individual tectonic regions are each characterized by a distinct range of attenuation and velocity values in the shallow upper mantle. Overall, lateral temperature variations can explain much of the observed variability in velocity and attenuation. The seismological velocity-attenuation relationship for oceanic regions agrees with the experimental observations at depths > 100 km and indicates lateral temperature variations of 150°-200 °C at 150 and 200 km beneath the seafloor. The seismic properties of cratonic regions deviate from the experimental trends at depths < 250 km, suggesting differences between oceanic and cratonic composition or water content at these depths. Globally, seismic properties shift into better agreement with the mineral-physics data at depths of ~ 125 km and ~ 225 km beneath oceans and cratons, respectively, which may indicate the base of a compositional boundary layer.
Dalton Colleen A.
Dziewonski Adam M.
Ekström Göran
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