HR: 1340h
AN: MR23A-0177    [Abstracts]
TI: The effect of temperature on the seismic anisotropy of the perovskite and post-perovskite polymorphs of MgSiO$_{3}$
AU: Stackhouse, S
EM: s.stackhouse@ucl.ac.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT United Kingdom
AU: Brodholt, J P
EM: j.brodholt@ucl.ac.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT United Kingdom
AU: Price, G D
EM: d.price@ucl.ac.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT United Kingdom
AU: * Wookey, J M
EM: j.wookey@earth.leeds.ac.uk
AF: School of Earth Sciences, University of Leeds, Leeds, LS2 9JT United Kingdom
AU: Kendall, J
EM: m.kendall@earth.leeds.ac.uk
AF: School of Earth Sciences, University of Leeds, Leeds, LS2 9JT United Kingdom
AB: Using elastic constants determined by ab initio molecular dynamics over a range of temperatures, we show that the seismic anisotropy of MgSiO$_{3}$ perovskite is significantly temperature dependent. At 90 GPa, the direction of greatest shear wave splitting changes from [001] at 0 K, to [010] at 3500 K. In addition, there is no shear wave splitting in the [100] direction at 0K, but a significant amount of splitting is exhibted at 3500 K. We have also calculated the first set of high-temperature elastic constants of the new post-perovskite phase by ab initio molecular dynamics methods. We find that, in contrast to MgSiO$_{3}$ perovskite, temperature has little effect on the acoustic anisotropy of this phase. We determine ($\partial$lnV$_{S}$/$\partial$lnV$_{P}$)$_{P}$ for the post-perovskite phase and find it to be very low at about 0.9.
UR: http://www.es.ucl.ac.uk/research/desmond/
DE: 5102 Acoustic properties
DE: 7207 Core and mantle
DE: 3909 Elasticity and anelasticity
DE: 3924 High-pressure behavior
DE: 1212 Earth's interior--composition and state (8105)
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting