Computer Science – Sound
Scientific paper
Aug 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004pepi..146...87k&link_type=abstract
Physics of the Earth and Planetary Interiors, Volume 146, Issue 1-2, p. 87-100.
Computer Science
Sound
15
Mantle, Bulk-Sound, Wavespeed
Scientific paper
The primary source of information on heterogeneity within the Earth comes from seismic tomography. A powerful tool for examining the character of heterogeneity comes from the comparison of images of bulk-sound and shear wavespeed extracted in a single inversion, since this isolates the dependencies on the elastic moduli. However, particularly in such multi-parameter inversions there are many hidden facets which can have a strong influence on the results, such as the weightings between parameters and in the misfit functions. Joint inversion with restricted data sets giving comparable cover for P and S waves provides useful checks on more inclusive studies, and can provide relatively high resolution in some areas. The relative behaviour of bulk-sound and shear wavespeed can provide a useful guide to the definition of heterogeneity regimes. For subduction zones a large part of the tomographic signal comes from S wavespeed variations. In the upper mantle and transition there can be significant bulk-sound speed contributions for younger slabs, and in stagnant slabs associated with slab roll-back. For subducted oceanic lithosphere older than about 90Ma shear wavespeed variations nearly always are dominant and so the P wave images are controlled by shear modulus variations. The narrow segments of fast wavespeeds in the depth range 900-1500km in the lower mantle are dominated by S variations, with very little bulk-sound contribution. Deep in the mantle there are many fast features without obvious association with subduction in the last 100Ma, which suggests long-lived preservation of components of the geodynamic cycle.
Current address: JAMSTEC, Yokohama, Japan.
Gorbatov Alexei
Kennett Brian L. N.
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