HR: 1340h
AN: S13A-0187    [Abstracts]
TI: 3-D Global Seismic Wavefields Computed Using 2-D Spectral-Elements: A Basis for Exact Sensitivity Kernels
AU: * Nissen-Meyer, T
EM: tarje@princeton.edu
AF: Princeton University, Department of Geosciences, Guyot Hall, Princeton, NJ 08544 United States
AU: Fournier, A
EM: Alexandre.Fournier@obs.ujf-grenoble.fr
AF: Université Joseph Fourier, Laboratoire de Géophysique Interne et Tectonophysique, 38041 Grenoble, Cedex 9 France
AU: Dahlen, F
EM: fad@princeton.edu
AF: Princeton University, Department of Geosciences, Guyot Hall, Princeton, NJ 08544 United States
AB: We developed a spectral-element approach to solve the 3-D seismic wave propagation problem upon spherically symmetric earth models for a full seismic moment tensor in a 2-D domain. This technique serves as the crux to efficiently compute full Fréchet sensitivity kernels in a spherical earth up to high frequencies while accounting for all wavefield features including diffracted phases and triplications. The underlying idea is the decomposition of moment tensors (i.e. earthquake sources) and single forces (i.e. receiver components using reciprocity) into six constituents with known azimuthal radiation patterns. For a given source location, these independent 2-D problems are solved to reconstruct the full Green tensor and its spatial derivatives. We describe the variational formulation for this multipole system upon spherically symmetric earth models along with its discretization based upon spectral elements in a cylindrical domain. The algorithm is highly optimized and runs in parallel using a flexible and efficient domain decomposition strategy and message passing. To demonstrate its expedience and accuracy, we address several aspects of the method separately: Using toroidal eigenfunctions as a solution to the source-free elastostatic problem, we show high spatial accuracy throughout the domain and spectral convergence for dipole and quadrupole systems. The source implementation and accuracy in the immediate source vicinity is investigated using the analytical elastodynamic solution for infinite, homogeneous media. Finally, seismogram sections show high accuracy for all distances, phases, and source types utilizing normal mode summation as a reference.
DE: 0560 Numerical solutions (4255)
DE: 7203 Body waves
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7260 Theory
DE: 7290 Computational seismology
SC: Seismology [S]
MN: Fall Meeting 2005