HR: 0800h
AN: S31B-1040    [Abstracts]
TI: Finite-Frequency Sensitivity Kernels for Boundary Topography Perturbations
AU: * Dahlen, F A
EM: fad@princeton.edu
AF: Department of Geosciences, Princeton University, Princeton, NJ 08544 United States
AB: Seismic traveltimes are sensitive not only to three-dimensional wavespeed variations, but also to the topography of internal discontinuity surfaces within the earth. This sensitivity has been exploited in a number of tomographic investigations, beginning with the largely unsuccessful attempts to infer the long-wavelength topography of the core-mantle boundary using the ISC-archived traveltimes of {\textit PcP\/} and {\textit PKP\/} waves. More recent studies have focused upon the topography of the major upper-mantle discontinuities and the thickness of the transition zone between 410 and 660 km depth, using the traveltimes of {\textit SdS\/} and {\textit PdP\/} bottomside reflections and {\textit Pds\/} conversions. All of these studies are based upon infinite-frequency ray theory, which maps a traveltime perturbation to the topographic perturbation at a single point on the source-to-receiver geometrical ray. A number of workers have questioned the applicability of ray theory to finite-frequency {\textit SdS\/} traveltimes, because the X-shaped Fresnel zones of off-ray sensitivity are particularly extensive for these minimax-time waves. In this paper, we use the Born approximation in conjunction with body-wave ray theory to derive a finite-frequency, boundary-topography Fr\'{e}chet kernel that fully accounts for the off-ray sensitivity of a transmitted, reflected or converted wave.
DE: 7260 Theory and modeling
DE: 7203 Body wave propagation
SC: Seismology [S]
MN: 2004 AGU Fall Meeting