Shear velocity variation within the D″ region beneath the central Pacific

Megan Avants, Thorne Lay, Sara Russell Gonzalez, Edward Garnero

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

Small-scale variability of shear velocity (Vs) structure in the D″ region beneath the central Pacific is imaged using 442 broadband tangential component S waveforms recorded in western North America for 37 intermediate and deep focus Tonga-Fiji earthquakes. Double-array stacking of spatially binned subsets of data reveals lateral variations in the relative timing and amplitude of deep mantle discontinuity reflections on scale lengths of about 130 km across the ∼6° × 8° region of D″ sampled. Waveform modeling using localized one-dimensional structures indicates variations of the Vs increase at the D″ discontinuity ranging from 0.5% to 2.3%, and discontinuity depths ranging from 2490 to 2735 km, deepening and weakening from southwest-to-northeast across the study area. Two abrupt Vs reductions are also detected within the D″ layer. We thus present a laterally variable three-layer model of the D″ region beneath the central Pacific. The complex structure may be associated with lateral thermal and chemical gradients that produce a lens of postperovskite material above an ultralow-velocity zone on the margin of a large low shear velocity province.

Original languageEnglish (US)
Article numberB05305
JournalJournal of Geophysical Research: Solid Earth
Volume111
Issue number5
DOIs
StatePublished - May 4 2006

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D region
discontinuity
shear
waveforms
mantle discontinuity
velocity structure
stacking
set theory
margins
Lenses
Earthquakes
Earth mantle
earthquakes
lenses
time measurement
broadband
earthquake
gradients
modeling

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Atmospheric Science
  • Astronomy and Astrophysics
  • Oceanography

Cite this

Shear velocity variation within the D″ region beneath the central Pacific. / Avants, Megan; Lay, Thorne; Gonzalez, Sara Russell; Garnero, Edward.

In: Journal of Geophysical Research: Solid Earth, Vol. 111, No. 5, B05305, 04.05.2006.

Research output: Contribution to journalArticle

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AB - Small-scale variability of shear velocity (Vs) structure in the D″ region beneath the central Pacific is imaged using 442 broadband tangential component S waveforms recorded in western North America for 37 intermediate and deep focus Tonga-Fiji earthquakes. Double-array stacking of spatially binned subsets of data reveals lateral variations in the relative timing and amplitude of deep mantle discontinuity reflections on scale lengths of about 130 km across the ∼6° × 8° region of D″ sampled. Waveform modeling using localized one-dimensional structures indicates variations of the Vs increase at the D″ discontinuity ranging from 0.5% to 2.3%, and discontinuity depths ranging from 2490 to 2735 km, deepening and weakening from southwest-to-northeast across the study area. Two abrupt Vs reductions are also detected within the D″ layer. We thus present a laterally variable three-layer model of the D″ region beneath the central Pacific. The complex structure may be associated with lateral thermal and chemical gradients that produce a lens of postperovskite material above an ultralow-velocity zone on the margin of a large low shear velocity province.

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