%0 Journal Article
%T Elastic and anelastic structure of the lowermost mantle beneath the Western Pacific from waveform inversion
%+ Institut de Physique du Globe de Paris (IPGP)
%A Konishi, Kensuke
%A Fuji, Nobuaki
%A Deschamps, Frédéric
%< avec comité de lecture
%@ 0956-540X
%J Geophysical Journal International
%I Oxford University Press (OUP)
%V 208
%P 1290-1304
%8 2017
%D 2017
%Z 2017GeoJI.208.1290K
%R 10.1093/gji/ggw450
%K Inverse theory
%K Elasticity and anelasticity
%K Body waves
%K Seismic attenuation
%K Seismic tomography
%K Pacific Ocean
%Z Sciences of the Universe [physics]
%Z Sciences of the Universe [physics]/Earth SciencesJournal articles
%X We investigate the elastic and anelastic structure of the lowermost mantle at the western edge of the Pacific large low shear velocity province (LLSVP) by inverting a collection of S and ScS waveforms. The transverse component data were obtained from F-net for 31 deep earthquakes beneath Tonga and Fiji, filtered between 12.5 and 200 s. We observe a regional variation of S and ScS arrival times and amplitude ratios, according to which we divide our region of interest into three subregions. For each of these subregions, we then perform 1-D (depth-dependent) waveform inversions simultaneously for radial profiles of shear wave velocity (VS) and seismic quality factor (Q). Models for all three subregions show low VS and low Q structures from 2000 km depth down to the core-mantle boundary. We further find that VS and Q in the central subregion, sampling the Caroline plume, are substantially lower than in the surrounding regions, whatever the depth. In the central subregion, VS-anomalies with respect to PREM (dVS) and Q are about -2.5 per cent and 216 at a depth of 2850 km, and -0.6 per cent and 263 at a depth of 2000 km. By contrast, in the two other regions, dVS and Q are -2.2 per cent and 261 at a depth of 2850 km, and -0.3 per cent and 291 at a depth of 2000 km. At depths greater than ∼2500 km, these differences may indicate lateral variations in temperature of ∼100 K within the Pacific LLSVP. At shallower depths, they may be due to the temperature difference between the Caroline plume and its surroundings, and possibly to a small fraction of iron-rich material entrained by the plume.
%G English
%2 https://insu.hal.science/insu-03748871/document
%2 https://insu.hal.science/insu-03748871/file/ggw450.pdf
%L insu-03748871
%U https://insu.hal.science/insu-03748871
%~ INSU
%~ UNIV-PARIS7
%~ AFRIQ
%~ CNRS
%~ IPGP
%~ USPC
%~ SORBONNE-UNIVERSITE
%~ UNIV-PARIS
%~ SU-TI
%~ ALLIANCE-SU