HR: 0800h
AN: S51E-1052    [Abstracts]
TI: Multi-Mode Surface-Waveform Tomography of the Pacific Region: Model Validation and the Lithospheric Cooling Signature.
AU: * Maggi, A
EM: alessia@gps.caltech.edu
AF: Seismo Lab California Institute of Technology, 1200 E California Blvd MS 252 - 21, Pasadena, CA 91125 United States
AU: Tromp, J
EM: jtromp@gps.caltech.edu
AF: Seismo Lab California Institute of Technology, 1200 E California Blvd MS 252 - 21, Pasadena, CA 91125 United States
AU: Debayle, E
EM: eric.debayle@eost.u-strasbg.fr
AF: Ecole et Observatoire des Sciences de la Terre, 5 rue Rene Descartes, Strasbourg, 67084 France
AU: Barruol, G
EM: barruol@upf.pf
AF: Jeune Equipe Terre-Océan Université de la Polynésie française BP 6570, Tahiti, Polynesie Francaise, Faaa, Tahiti, BP 6570 French Polynesia
AB: We present an anisotropic Sv-wave speed tomographic model for the Pacific Ocean region derived from multi-mode waveform inversion of more than 56,000 vertical component seismograms. Most of the data are from the Global Seismic Network, but we include important data from ten broadband seismographs deployed in French Polynesia as part of the Polynesian Lithosphere and Upper Mantle Experiment. This extra data has improved lateral resolution in the south Pacific region, leading to the identification of localized, vertically trending low velocity anomalies associated with the Society and Macdonald hot-spots. An age-dependent average cross-section of our tomographic model shows the lithosphere thickening and cooling with increasing age as predicted by a purely diffusive cooling mechanism. The tomography was performed assuming 2D frequency-independent Gaussian-shaped sensitivity kernels around the surface wave ray-paths, and ray-theoretical depth dependence of the surface wave sensitivity. We validate the 3D tomographic model by calculating full 3D synthetic seismograms using the spectral element method. We estimate the quality of our tomographic inversion by making multi-taper phase and amplitude measurements of the differences between observed seismograms and 3D synthetics. Preliminary inversion of such measurements made on fundamental mode surface waves indicates that the residual discrepancies between our 3D tomographic model and the real Earth structure are localized in regions of strong upper mantle heterogeneity (e.g. subduction zones), for which the ray-theoretical approximations made during the tomographic inversion are most likely to break down.
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7218 Lithosphere (1236)
DE: 7255 Surface waves and free oscillations
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: Fall Meeting 2005