HR: 0800h
AN: S51A-0993    [Abstracts]
TI: Assessment of Finite-Frequency Theory for Regional Surface Wave Tomography
AU: * Sieminski, A
EM: anne@geo.uu.nl
AF: Department of Earth Sciences, Utrecht University, P.O. Box 80.021, Utrecht, 3508 TA Netherlands
AU: Lévêque, J
EM: JeanJacques.Leveque@eost.u-strasbg.fr
AF: Institut de Physique du Globe de Strasbourg, 5 rue Rene Descartes, Strasbourg Cedex, 67084 France
AU: Debayle, E
EM: Eric.Debayle@eost.u-strasbg.fr
AF: Institut de Physique du Globe de Strasbourg, 5 rue Rene Descartes, Strasbourg Cedex, 67084 France
AB: To map small scale heterogeneties more reliably, many recent works propose to go beyond ray theory using more accurate finite-frequency propagation theories. However, while any finite-frequency theory is better than ray theory in forward modelling, it is not obvious that a finite-frequency theory will lead to a better image through an inversion process. We compare here ray theory and finite-frequency theory for surface wave tomography both with synthetic data and with a regional real dataset. Our finite-frequency theory only considers near forward, single scattering without mode coupling. Moving from ray theory to finite-frequency theory also requires to reconsider the regularization of the inversion. For a better imaging of small scale structures, finite-frequency theory should ideally be applied without a priori lateral smoothing. This works well with synthetic noiseless data, but does not lead to satisfactory results when applied to real data, showing that finite-frequency inversions are still ill-posed, likely because of the noise in the data. In the real data case, a priori lateral smoothing is thus necessary which implies no improvement in imaging. This suggests that refining the theory only is not sufficient to significantly improve tomography.
DE: 3260 Inverse theory
DE: 3285 Wave propagation (0689, 2487, 4275, 4455, 6934)
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7255 Surface waves and free oscillations
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: Fall Meeting 2005