HR: 0800h
AN: U41B-0405 [Abstracts]
TI: Structure of the Edge of the Pacific Low-Velocity Feature Investigated Using Philippine Source Array
AU: * Chaloner, J
EM: j.chaloner@liv.ac.uk
AF: University of Liverpool, Department of Earth and Ocean Sciences
Univeristy of Liverpool
4 Brownlow Street, Liverpool, L69 3GP, United Kingdom
AU: Thomas, C
EM: tine@liv.ac.uk
AF: University of Liverpool, Department of Earth and Ocean Sciences
Univeristy of Liverpool
4 Brownlow Street, Liverpool, L69 3GP, United Kingdom
AU: Rietbrock, A
EM: a.rietbrock@liv.ac.uk
AF: University of Liverpool, Department of Earth and Ocean Sciences
Univeristy of Liverpool
4 Brownlow Street, Liverpool, L69 3GP, United Kingdom
AB:
The D region of the lowermost mantle has been much studied in recent years, since understanding of its
structure will shed light on mantle convection systems and core-mantle interactions. In particular, the role of the
post-perovskite phase transition in creating the seismic discontinuities in D has been the focus of much
interest, along with the suggestion that the large scale seismic velocity reductions under Africa and the central
Pacific may be due to piles of chemically and thermally distinct material.
We investigate D structure under the western Pacific, north-west of the Marshall Islands, by using earthquakes
in the Philippine Sea recorded in Hawaii to construct source arrays. These events have core-mantle boundary
bounce points which sample across the edge of the central Pacific low-velocity region found in seismic
tomography of the lowermost mantle. Selection of groups of earthquakes with suitably similar source
mechanisms and depths allows us to perform migrations of both P- and S-waves to show variations in the
seismic velocity structure of D across the edge of the low-velocity feature. This provides insight into the role of
post-perovskite, thermal and chemical heterogeneity in the behaviour of the lower mantle.
DE: 3924 High-pressure behavior
DE: 5430 Interiors (8147)
DE: 7203 Body waves
DE: 7208 Mantle (1212, 1213, 8124)
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
SC: Union [U]
MN: 2007 Fall Meeting