HR: 0800h
AN: DI31A-0259    [Abstracts]
TI: New estimate of the inner-outer core density ratio from previously unobserved steep- incidence inner core reflections
AU: * Tkalcic, H
EM: Hrvoje.Tkalcic@anu.edu.au
AF: Research School of Earth Sciences, The Australian National University, Buiding 61 Mills Road, Canberra, ACT 0200, Australia
AU: Kennett, B L
EM: Brian.Kennett@anu.edu.au
AF: Research School of Earth Sciences, The Australian National University, Buiding 61 Mills Road, Canberra, ACT 0200, Australia
AB: The density contrast at the inner-outer core boundary, which has significant geodynamical implications, has long been a subject of controversial findings. Seismological 1D models of the Earth indicate that this contrast is larger than it would be for just a phase transition. However, until recently, seismological studies using body waves and normal modes have given significantly different values for this ratio. When the ray theory is used, part of the problem lies in the fact that the convincing observations of PKiKP and PcP for epicentral distances less than 70 degrees are extremely rare. The relative amplitudes will be particularly sensitive to attenuation and radiation patterns, that are not indentical in the mantle. For short distances the mantle components are almost in common, and so the estimates of density conrasts should be most reliable. We report new observations of clear PKiKP arrivals at very short epicentral distances, sampling nearly the same path from the source to the reflection point and from the reflection point to the receiver . These observations are result of a systematic analysis of a global dataset of IRIS Passcal seismic broadband waveforms. We examine the propagations characteristics for the major discontinuities using ray theory and synthetic seismograms based on a reflectivity technique.
DE: 1212 Earth's interior: composition and state (7207, 7208, 8105, 8124)
DE: 1213 Earth's interior: dynamics (1507, 7207, 7208, 8115, 8120)
DE: 3924 High-pressure behavior
DE: 7207 Core (1212, 1213, 8124)
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting