HR: 0830h
AN: U51B-0004    [PDF]
TI: Generalized Radon Transform Inversion of Coda Waves: Imaging Selected Neighborhoods of the CMB
AU: * Wang, P
EM: wangp@mit.edu
AF: Massachusetts Institue of Technology, 54-526, 77 Mass. Ave., Cambridge, MA 02139 United States
AU: De Hoop, M V
EM: mdehoop@mines.edu
AF: Colorada School of Mines, CWP, Golden, CO 80401 United States
AU: van der Hilst, R D
EM: hilst@mit.edu
AF: Massachusetts Institue of Technology, 54-526, 77 Mass. Ave., Cambridge, MA 02139 United States
AB: Different forward and inverse methods have been used to image the multi-scale heterogeneity in the lowermost mantle. In this paper we use generalized Radon transform,which is developed from microlocal analysis and the theory of Fourier integral operators, to carry out inversion of scattered seismic body waves, such as ScS and SKKS. We believe this method can better characterize the variations of acousto-elastic properties of the physical shell that encompasses Earth's lowermost mantle (the so-called D" region), the core-mantle (CMB), and Earth's outer core. We assume that the structure of the mantle outside this shell is sufficiently well known from seismic body wave transmission tomography and from the free oscillation frequencies. To illustrate the concepts of the generalized Radon transform method, we apply it to a particular downwelling region - Central America. In this study we choose a bin of size of 12$^{o}$ $\times$ 12$^{o}$ (600 km $\times$ 600 km). All the rays that have a mid point in this bin will be used to get image of the center (longitude: -90, latitude: 15) of this bin. Our final image gathers indicate: i) the inversion of both ScS and SKKS results a clear CMB; ii) there exists a clear discontinuity at about 260 km above the CMB; iii) there is probably a discontinuity (or scatteres) at about 50 km above the CMB; iv) the S-wave velocity of the lowermost mantle is higher than the globally estimated average S-wave velocity model.
DE: 7207 Core and mantle
SC: U
MN: 2003 Fall Meeting