HR: 08:00h
AN: DI51B-01 INVITED    [Abstracts]
TI: Insights on Compositional and Thermal Structure of the Earth's Upper Mantle Using Mineral Physics and Seismic Data.
AU: * Cammarano, F
EM: fabio@seismo.berkeley.edu
AF: UC Berkeley, 215 Mc Cone Hall, Berkeley, CA 94720, United States
AU: romanowicz, B
EM: barbara.romanowicz@gmail.com
AF: UC Berkeley, 215 Mc Cone Hall, Berkeley, CA 94720, United States
AU: Deuss, A
EM: afd28@cam.ac.uk
AF: Cambridge University, Downing Street, Cambridge, CB30EZ, United Kingdom
AU: Goes, S
EM: s.goes@imperial.ac.uk
AF: Imperial College, South Kensington Campus, London, SW72AZ, United Kingdom
AB: Temperature and composition of the Earth's mantle are key factors to understand the dynamics of Earth's interior. Interdisciplinary studies that profit of the parallel advances on studies of material properties at high pressure (and temperature) and seismology are needed to improve the knowledge of these fundamental physical parameters. We present published and preliminary results from different studies based on such an approach, focusing on global average constraints. First, we show how well an adiabatic pyrolite model fits global seismic data by accounting for the full range of uncertainties on elastic and anelastic properties of mantle minerals. We found a small set of "best-fitting" models, all seismically very similar, that can be used as starting models for seismic inversion. Second, we show the results of a global seismic waveform inversion that adopts one of these physical models instead of commonly used seismic reference models (e.g. PREM) as starting model. Absolute shear velocities and gradients with depth are well constrained by long period seismic waveforms throughout the upper mantle, except near discontinuities. We found a high velocity gradient between 250 and 350km that cannot be explained with any realistic thermal structure, assuming than composition does not change with depth. A gradual enrichment in garnet with depth may help. Third, we use SS and PP precursors in order to provide a better characterization of the seismic structure around the 400 and 660 km discontinuities. Relative amplitudes between the discontinuity reflections and the reference phases SS and PP are evaluated.
DE: 3909 Elasticity and anelasticity
DE: 7200 SEISMOLOGY
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7255 Surface waves and free oscillations
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting