Upper and mid-mantle anisotropy beneath the Tonga slab

Bradford James Foley, Maureen D. Long

Research output: Contribution to journalArticle

57 Citations (Scopus)

Abstract

Measurements of source-side splitting in S waves from events within the Tonga slab reveal anisotropy in the upper and mid-mantle beneath the slab. We observed splitting for events originating at both upper mantle and transition zone depths. Anisotropic fast directions (θ) are trench parallel or sub-parallel for both upper mantle and transition zone events. Delay times (δt) decrease with depth for upper mantle events. The source of anisotropy for the upper mantle events is likely in the sub-slab mantle, and is likely indicative of trench parallel flow due to slab rollback. The source of anisotropy for the deeper earthquakes is more difficult to constrain, but the pattern of splitting measurements argues for an uppermost lower mantle anisotropic source, and slab induced deformation may be responsible for this anisotropy as well. Additional constraints from mineral physics studies are necessary to interpret the mid-mantle anisotropy signal in terms of geodynamical processes.

Original languageEnglish (US)
Article numberL02303
JournalGeophysical Research Letters
Volume38
Issue number2
DOIs
StatePublished - Jan 1 2011

Fingerprint

slab
Earth mantle
slabs
anisotropy
upper mantle
mantle
transition zone
trench
lower mantle
S-wave
physics
parallel flow
earthquake
S waves
mineral
time lag
earthquakes
minerals

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

Cite this

@article{0e16afc70d33475a8be4c9c29b251767,
title = "Upper and mid-mantle anisotropy beneath the Tonga slab",
abstract = "Measurements of source-side splitting in S waves from events within the Tonga slab reveal anisotropy in the upper and mid-mantle beneath the slab. We observed splitting for events originating at both upper mantle and transition zone depths. Anisotropic fast directions (θ) are trench parallel or sub-parallel for both upper mantle and transition zone events. Delay times (δt) decrease with depth for upper mantle events. The source of anisotropy for the upper mantle events is likely in the sub-slab mantle, and is likely indicative of trench parallel flow due to slab rollback. The source of anisotropy for the deeper earthquakes is more difficult to constrain, but the pattern of splitting measurements argues for an uppermost lower mantle anisotropic source, and slab induced deformation may be responsible for this anisotropy as well. Additional constraints from mineral physics studies are necessary to interpret the mid-mantle anisotropy signal in terms of geodynamical processes.",
author = "Foley, {Bradford James} and Long, {Maureen D.}",
year = "2011",
month = "1",
day = "1",
doi = "10.1029/2010GL046021",
language = "English (US)",
volume = "38",
journal = "Geophysical Research Letters",
issn = "0094-8276",
publisher = "American Geophysical Union",
number = "2",

}

Upper and mid-mantle anisotropy beneath the Tonga slab. / Foley, Bradford James; Long, Maureen D.

In: Geophysical Research Letters, Vol. 38, No. 2, L02303, 01.01.2011.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Upper and mid-mantle anisotropy beneath the Tonga slab

AU - Foley, Bradford James

AU - Long, Maureen D.

PY - 2011/1/1

Y1 - 2011/1/1

N2 - Measurements of source-side splitting in S waves from events within the Tonga slab reveal anisotropy in the upper and mid-mantle beneath the slab. We observed splitting for events originating at both upper mantle and transition zone depths. Anisotropic fast directions (θ) are trench parallel or sub-parallel for both upper mantle and transition zone events. Delay times (δt) decrease with depth for upper mantle events. The source of anisotropy for the upper mantle events is likely in the sub-slab mantle, and is likely indicative of trench parallel flow due to slab rollback. The source of anisotropy for the deeper earthquakes is more difficult to constrain, but the pattern of splitting measurements argues for an uppermost lower mantle anisotropic source, and slab induced deformation may be responsible for this anisotropy as well. Additional constraints from mineral physics studies are necessary to interpret the mid-mantle anisotropy signal in terms of geodynamical processes.

AB - Measurements of source-side splitting in S waves from events within the Tonga slab reveal anisotropy in the upper and mid-mantle beneath the slab. We observed splitting for events originating at both upper mantle and transition zone depths. Anisotropic fast directions (θ) are trench parallel or sub-parallel for both upper mantle and transition zone events. Delay times (δt) decrease with depth for upper mantle events. The source of anisotropy for the upper mantle events is likely in the sub-slab mantle, and is likely indicative of trench parallel flow due to slab rollback. The source of anisotropy for the deeper earthquakes is more difficult to constrain, but the pattern of splitting measurements argues for an uppermost lower mantle anisotropic source, and slab induced deformation may be responsible for this anisotropy as well. Additional constraints from mineral physics studies are necessary to interpret the mid-mantle anisotropy signal in terms of geodynamical processes.

UR - http://www.scopus.com/inward/record.url?scp=79251573915&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79251573915&partnerID=8YFLogxK

U2 - 10.1029/2010GL046021

DO - 10.1029/2010GL046021

M3 - Article

AN - SCOPUS:79251573915

VL - 38

JO - Geophysical Research Letters

JF - Geophysical Research Letters

SN - 0094-8276

IS - 2

M1 - L02303

ER -