HR: 0800h
AN: DI31A-0245    [Abstracts]
TI: Heterogeneity in Inner Core Anisotropy
AU: * Irving, J C
EM: jcei2@cam.ac.uk
AF: Bullard Laboratories, University of Cambridge, Madingley Road, Cambridge, CB3 0EZ, United Kingdom
AU: Deuss, A
EM: deuss@esc.cam.ac.uk
AF: Bullard Laboratories, University of Cambridge, Madingley Road, Cambridge, CB3 0EZ, United Kingdom
AU: Woodhouse, J
EM: john.woodhouse@earth.ox.ac.uk
AF: Department of Earth Sciences, Oxford University, Parks Road, Oxford, OX1 3PR, United Kingdom
AB: A number of previous studies have investigated the existence of seismic anisotropy in the Earth's inner core. This anisotropic nature has been modelled using free oscillation data with widely varying results, which are formally inconsistent with each other. All of these models derived from normal mode data have been developed using a self coupling approximation which ignores the significance of coupling of different inner core modes through the anisotropic structure. This self coupling approximation of normal modes is not reliable for mantle structure (Deuss & Woodhouse 2001), here we show that this is also the case for the inner core. Body waves travelling through the inner core also show anisotropic behaviour; wave speed in the North-South direction is greater that in the equatorial plane. These differences can be readily seen in the differential travel times between waves which bottom in the outer core and those which penetrate into the inner core. Both PKPbc- PKPdf differential travel times and PKPab-PKPdf differential travel times display this anisotropy. Using these differential travel times, we find that there are lateral differences in the anisotropy of the inner core. Coupling of normal modes due to such lateral heterogeneity in the inner core should be observable in normal mode spectra. At present there are inconsistencies between the body wave and normal mode data which must be resolved. By comparing body wave and normal mode data with inner core anisotropy models we hope to find a picture of inner core anisotropy that is consistent with the seismic observations. Such information is a prerequisite for the integration of results from seismology and mineral physics, with the aim of establishing the details and causes of inner core anisotropy.
DE: 5430 Interiors (8147)
DE: 7200 SEISMOLOGY
DE: 7203 Body waves
DE: 7207 Core (1212, 1213, 8124)
DE: 7255 Surface waves and free oscillations
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting