HR: 0800h
AN: S31B-1043    [Abstracts]
TI: Tomography of the global Earth based on the Spetral Elements Method
AU: * Capdeville, Y
EM: capdevil@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, Departement de sismologie 4 place Jussieu T24-14, Case 89, Paris cedex 05, 75252 France
AU: Gung, Y
EM: ycgung@ntu.edu.tw
AF: National Taiwan University, Department of Geoscience, National Taiwan University, Taiwan, Taipei, 106 Taiwan
AU: Romanowicz, B
EM: barbara@seismo.berkeley.edu
AF: Berkeley Seismological Lab. UC Berkeley, MacCone Hall UC Berkeley, Berkeley, CA 94720-4760 United States
AB: We present a new tomographic method based on the non linear least squares inversion of seismograms using the spectral elements method (SEM). The SEM is used for the forward modeling and to compute partial derivatives of seismograms with respect to the model parameters. The main idea of the method is to use a special data reduction scheme to overcome the prohibitive numerical cost of such a inversion. The SEM allows us to trigger several sources at the same time within one simulation with no incremental numerical cost. Doing so, the resulting synthetic seismograms are the sum of seismograms due to each individual source for a common receiver and a common origin time, with no possibility to separate them afterward. These summed synthetics are not directly comparable to data, but using the linearity of the problem with respect to the seismic sources, we can sum all data for a common station and a common zero time, and we perform the same operation on synthetics. Using this data reduction scheme, we can then model the whole dataset using a single SEM run, rather than a number of runs equal to the number of events considered, allowing this type of inversion to be feasible on a reasonable size computer. We will present different tests that show the feasibility of the method. It appears that this approach can work owing to the combination of two factors: the off-path sensitivity of the long period waveforms and the presence of multiple-scattering, which compensate for the loss of information in the summation process. We will discuss the advantages and drawbacks of such a scheme
DE: 7255 Surface waves and free oscillations
DE: 7260 Theory and modeling
DE: 3260 Inverse theory
DE: 0644 Numerical methods
SC: Seismology [S]
MN: 2004 AGU Fall Meeting