HR: 0800h
AN: S41C-1033    [Abstracts]
TI: Global P Travel-Time Tomography With an Extended Data Set and a 3-D Starting Model
AU: * Amaru, M L
EM: amaru@geo.uu.nl
AF: Department of Earth Sciences, Utrecht University, Budapestlaan 4, Utrecht, 3584CD Netherlands
AU: Spakman, W
S41C-1033 AF: Department of Earth Sciences, Utrecht University, Budapestlaan 4, Utrecht, 3584CD Netherlands
AU: Villasenor, A
S41C-1033 AF: Institute of Earth Sciences "Jaume Almera" - CSIC, Lluis Sole i Sabaris s/n, Barcelona, 08028 Spain
AU: Sandoval, S
S41C-1033 AF: Department of Earth Sciences, Utrecht University, Budapestlaan 4, Utrecht, 3584CD Netherlands
AU: Engdahl, E R
S41C-1033 AF: University of Colorado, Campus Box 390, Boulder, CO 80309 United States
AU: Kissling, E
S41C-1033 AF: Institute of Geophysics, ETH, Hoenggerberg, Zuerich, 8093 Switzerland
AB: We have obtained a global high-resolution P-wave velocity model for the crust and mantle by means of travel-time tomography. The data set consists of a subset of 420,000 well-located events from the ISC bulletins and NEIC data up to September 2004. The selection contains 18 million P travel-times and additionally 2 million core phases. Furthermore, we incorporated newly picked travel-times of recordings from seismic networks and temporary experiments in Europe and North America which do not report to the ISC. The picking was done with an automatic picker based on an adaptive stacking method. Methodologically, instead of a standard 1-D Earth reference model, we use a 3-D reference model based on a combination of CRUST2.0 and tomography models that use independent observations from surface waves, normal modes and long-period body-waves. The selected events are relocated in this 3-D reference model using a directed grid-search technique to establish consistency between travel-times and event parameters. Next, the rays are traced through the new reference model to account for ray bending due to 3-D heterogeneities in crust and mantle. The travel-time tomography is performed on an irregular cell-grid where the cell size depends on the number of rays crossing a cell with a lateral extension of the cells between 0.5 degrees and 5.0 degrees. Sensitivity tests show that in the uppermost mantle anomalies with a lateral extension of 0.5 degrees can be reconstructed for many regions while sensitivity to 3-D anomalies decreases with depth. Due to the additional data, more detail is particularly seen between 0 km and 400 km and the core phases help to constrain anomalies in the lowermost mantle. Our resulting model combines the long-wavelength structure as "seen" by long-period seismic information with the detailed mantle structure obtained from short-period data. Using a 3-D reference model also has the advantage, that the inversion model now implicitly contains more realistic velocities in areas that are not well constrained by P travel-times and can therefore improve travel-time prediction and earthquake relocation.
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: Fall Meeting 2005