HR: 13:40h
AN: V32E-01 INVITED     [PDF]
TI: Seismic tomography and mineral physics
AU: * Dziewonski, A M
EM: dziewons@eps.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138
AB: Information from mineral physics is essential in interpretation of results of seismic tomography in order to interpret them in terms of dynamic processes rather than a snapshot of the state of the mantle. On occasion, seismic tomography can provide independent, {\it in situ}, measurement of certain quantities; this was the case with the early tomographic estimates of $d \ln v_{S} / d \ln v_{P}$ to be about 2.0, while the mineral-physics estimate was 1.3. In general, however, interpretation of velocity perturbations in terms of changes in temperature, density or composition requires input from mineral physics. Over the last 20 years there has been significant progress in seismic tomography. Examples are the discovery of the anisotropy of the inner core, the anti-correlation of the bulk-sound and shear velocities in the lower mantle, and the unique anisotropy of the Pacific plate. At this time, some of the most spectacular tomographic results remain an enigma. For example, are the Pacific and African low-velocity mega-plumes an expression of higher temperature, and therefore lighter material, or of different composition, thus perhaps being heavier. Of course, linear combinations of these two end-member interpretations are also possible. In addition to the symbiotic relationship between mineral physics and seismology, there is also an important role for geodynamics, which must show that a model can reproduce the observed results, as well as for geochemistry, which has to verify that all available information is consistent with the geochemical data.
DE: 3900 MINERAL PHYSICS
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting