A new probe of ULVZ S-wave velocity stucture: Array stacking of ScS waveforms

Megan Avants, Thorne Lay, Edward Garnero

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

S-wave velocity reductions in thin layers above the core-mantle boundary (CMB) are resolved by modeling precursors to the tangential-components of core-reflected ScS phases. Unlike most phases used to study ultra-low velocity zone (ULVZ) structure, ScS provides direct sensitivity to shear velocity structure, VS. Recordings of deep earthquakes in the Tonga-Fiji and South American subduction zones at broadband seismic networks in western North America are used to map small-scale ULVZ variability. A two-layer low-VS structure exists under the central Pacific: an abrupt 0.8-2.0% decrease 60-86 km above the CMB is underlain by a 24-30 km thick ULVZ layer having reductions of 3.3-7.4% (with respect to PREM). No corresponding velocity reductions are found under the Cocos plate. The structure above the ULVZ may be associated with reverse transformation of post-perovskite to perovskite in a steep thermal gradient in a boundary layer above the CMB.

Original languageEnglish (US)
Article numberL07314
JournalGeophysical Research Letters
Volume33
Issue number7
DOIs
StatePublished - Apr 16 2006

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low velocity zone
stacking
core-mantle boundary
low speed
S waves
wave velocity
S-wave
waveforms
probe
probes
perovskite
Cocos plate
velocity structure
subduction zone
boundary layers
earthquakes
boundary layer
recording
shear
broadband

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

A new probe of ULVZ S-wave velocity stucture : Array stacking of ScS waveforms. / Avants, Megan; Lay, Thorne; Garnero, Edward.

In: Geophysical Research Letters, Vol. 33, No. 7, L07314, 16.04.2006.

Research output: Contribution to journalArticle

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