HR: 15:25h
AN: S33D-08    [Abstracts]
TI: Global model of P-wave speed variations in Earth's mantle
AU: * van der Hilst, R D
EM: hilst@mit.edu
AF: Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Li, C
EM: changli@quake.mit.edu
AF: Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AB: Using data from different seismic phases and improved tomography codes we have constructed a new model of 3-D variations in P-wavespeed in Earth's mantle. First, we improve data coverage by adding to the large volume of routinely processed ISC catalog (P, pP, PKP ) data, as reprocessed by Engdahl et al. (BSSA98), travel time residuals from several regional networks in SE Asia, several sets of differential travel times that have been measured by waveform cross correlation. These data include PKP-Pdiff (Wysession) and various PKP branches (Creager and McSweeney), which help improve resolution of structure in the deepest mantle, and PP-P (Bolton and Masters), which greatly improves the mapping of structure in the upper mantle away from belts of high seismic activity. Second, we follow Kerason et al. (JGR01) and use 3-D sensitivity kernels to account for the fact that these data are measured at different frequency, and in different ways. The kernels allow low frequency data (e.g., PP-P, Pdiff) to constrain long wavelengths without preventing short period data (P, PKP) to resolve small scale structure. We use approximate kernels since our research has shown that for this application the precise shape of the kernels is less important than effects of parameterization, regularization, and data quality. Third, the localization of sensitivity is further aided by the use of a grid that is adapted to sampling density. Fourth, for the ray geometry part we use 3-D ray tracing to account for the affects of heterogeneity on ray geometry. Finally, we correct for 3-D variations in crust structure, using the global model CRUST2.0 and more detailed regional models, where available. This correction reduces the artificial smearing of shallow structure along steep ray paths. We present the new model, along with resolution tests, and discuss differences and similarities with other global models, with emphasis on the structure of presumed 'slabs' of subducted lithosphere and 'plumes' of hotter-than-average material.
DE: 7200 SEISMOLOGY
DE: 7203 Body waves
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: Fall Meeting 2005