HR: 12:10h
AN: S52B-07    [Abstracts]
TI: A High-Resolution, Shear-Speed Model of the Upper Mantle
AU: * Lebedev, S
EM: sergei@geo.uu.nl
AF: Utrecht University, Earth Sciences, Utrecht, 3584 CD Netherlands
AU: van der Hilst, R D
EM: hilst@quake.mit.edu
AF: MIT, EAPS, Cambridge, MA 02139 United States
AB: Thanks to the expansion of seismographic networks within the last two decades and to the efforts being put at the IRIS data center into archiving, quality control, and distribution of the data, millions of top-quality earthquake recordings are now readily available from the center. One of the present challenges is to exploit more fully the resolving power of this extraordinary volume of data so as to increase further the resolution of tomographic imaging of the Earth. Here we process long-period, vertical-component seismograms recorded globally in 1994-2002 and available from the IRIS archives. We use the Automated Multimode Inversion of surface and S wave forms (Lebedev and Nolet, 2003), a technique aimed at (i) processing very large amounts of data, by making use of full automation; (ii) extracting the maximum of information from an S---surface wave train while ensuring that relevant approximations hold; (iii) balancing this information when relating it to Earth structure (in particular by weighting waves of different amplitudes and different types) so as to constrain unbiased Earth models. Waveform inversion enables mapping both the structure in the upper 200-300 km of the mantle (constrained primarily by the fundamental mode) and the transition-zone structure (constrained by regional S and multiple-S waves). The data sampling given by the 80,000 automatically selected and inverted seismograms is sufficient to achieve a resolution of a few hundred kilometers, varying with sampling density. The structure in the upper 100-300 km of the model correlates with the distribution of known tectonic elements, including backarc basins, spreading centers, and most cratons. Many of the recognized hotspots are underlain by low velocity anomalies extending as deep as the transition zone, which is consistent with a deep origin for the intraplate volcanism observed. We shall discuss selected features of the model in the presentation.
DE: 8180 Tomography
DE: 7218 Lithosphere and upper mantle
DE: 7260 Theory and modeling
DE: 7294 Instruments and techniques
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Seismology [S]
MN: 2004 AGU Fall Meeting