Anisotropic Shear-Wave Velocity Structure of the Earth's Mantle
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, B06306, doi:10.1029/2007JB005169, 2008 Click Here for Full Article Anisotropic shear-wave velocity structure of the Earth’s mantle: A global model B. Kustowski,1,2 G. Ekstro¨m,3 and A. M. Dziewon´ski1 Received 12 May 2007; revised 8 February 2008; accepted 14 March 2008; published 25 June 2008. [1] We combine a new, large data set of surface wave phase anomalies, long-period waveforms, and body wave travel times to construct a three-dimensional model of the anisotropic shear wave velocity in the Earth’s mantle. Our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model, simultaneous inversion for velocity and anisotropy, as well as discontinuity topographies, and implementation of nonlinear crustal corrections for waveforms. A comparison of our new three-dimensional model, S362ANI, with two other models derived from comparable data sets but using different techniques reveals persistent features: (1) strong, 200-km-thick, high-velocity anomalies beneath cratons, likely representing the continental lithosphere, underlain by weaker, fast anomalies extending below 250 km, which may represent continental roots, (2) weak velocity heterogeneity between 250 and 400 km depths, (3) fast anomalies extending horizontally up to 2000–3000 km in the mantle transition zone beneath subduction zones, (4) lack of strong long-wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle–lower mantle boundary, and (5) slow- velocity superplumes beneath the Pacific and Africa. The shear wave radial anisotropy is strongest at 120 km depth, in particular beneath the central Pacific.
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