HR: 0830h
AN: S31E-0816    [PDF]
TI: Simultaneous Inversion of Mantle Mode Splitting Coefficients for $V_s$, $V_p$ and $\rho$ Using the Neighbourhood Algorithm.
AU: * Rousset, S C
EM: rousset@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 225 McCone Hall, Berkeley, CA 94720 United States
AU: Romanowicz, B
EM: barbara@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 225 McCone Hall, Berkeley, CA 94720 United States
AB: Unlike travel times or waveform data, normal mode data are directly sensitive to the density of the Earth. However, the sensitivity kernels for density are much smaller than those for velocities, so the controversy about the possibility of resolution of the mantle's density is vivid, especially since the publication of model SPRD6 (Ishii and Tromp, 1999) whose high density structures corresponding with the "plumes" under Pacific and Africa would have important consequences on deep mantle dynamics. Using least squares inversion, several authors (e.g. Resovsky and Ritzwoller, 1999, Kuo and Romanowicz, 2002) pointed out significant trade-offs between velocity and density structure. Using a stochastic method may end the controversy about the resolution of density by estimating the posterior probability density of the parameter space. Such an approach was used by Resovsky and Ritzwoller (2002) who concluded in the non resolution of the density but did not investigate further. Here we investigate the effect of other parameterizations and of an extended dataset (Widmer, 2002). In particular, we look at the possibility of resolving a spline-based shear velocity model and the scaling relations $d(ln V_p)/d(ln V_s)$ and $d(ln \rho)/d(ln V_s)$. We search for 3 scaling parameters (lowermost, middle and upper mantle) and allow spatial variations of these parameters as each degree 2 spherical harmonic coefficient is considered separately. We present the results of the sampling of the parameter space and of the appraising of the ensemble generated in the form of marginal probabilities for the different parameters.
DE: 7207 Core and mantle
DE: 7255 Surface waves and free oscillations
SC: Seismology [S]
MN: 2003 Fall Meeting