insu-03748871
https://insu.hal.science/insu-03748871
https://insu.hal.science/insu-03748871/document
https://insu.hal.science/insu-03748871/file/ggw450.pdf
doi:10.1093/gji/ggw450
[INSU] INSU - Institut National des Sciences de l'Univers
[UNIV-PARIS7] Université Denis Diderot - Paris VII
[AFRIQ] HAL-Francophonie, Afrique et océan indien
[CNRS] CNRS - Centre national de la recherche scientifique
[IPGP] Institut de Physique du Globe de Paris
[USPC] Université Sorbonne Paris Cité
[SORBONNE-UNIVERSITE] Sorbonne Université
[UNIV-PARIS] Université Paris Cité
[SU-TI] Sorbonne Université - Texte Intégral
[ALLIANCE-SU] Alliance Sorbonne Université
Elastic and anelastic structure of the lowermost mantle beneath the Western Pacific from waveform inversion
Konishi, Kensuke
Fuji, Nobuaki
Deschamps, Frédéric
[SDU] Sciences of the Universe [physics]
[SDU.STU] Sciences of the Universe [physics]/Earth Sciences
ART
Inverse theory
Elasticity and anelasticity
Body waves
Seismic attenuation
Seismic tomography
Pacific Ocean
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 (V<SUB>S</SUB>) and seismic quality factor (Q). Models for all three subregions show low V<SUB>S</SUB> and low Q structures from 2000 km depth down to the core-mantle boundary. We further find that V<SUB>S</SUB> 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, V<SUB>S</SUB>-anomalies with respect to PREM (dV<SUB>S</SUB>) 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, dV<SUB>S</SUB> 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.
2017
2022-08-10
en
http://creativecommons.org/licenses/by/
Geophysical Journal International
Oxford University Press (OUP)