Seismic detection of a thin laterally varying boundary layer at the base of the mantle beneath the central-Pacific

Edward Garnero, Donald V. Helmberger

Research output: Contribution to journalArticle

143 Citations (Scopus)

Abstract

We explore lowermost mantle structure beneath the Pacific with long-period recordings of the seismic core phases SKS, SPdKS, and SKKS from 25 deep earthquakes. SPdKS and SKKS are anomalously delayed relative to SKS for lower mantle paths beneath the southwest Pacific. Late SPdKS arrivals are explained by a laterally varying mantle-side boundary layer at the CMB, having P-velocity reductions of up to 10% and thickness up to 40 km. This layer is detected beneath a tomographically resolved large-scale low velocity feature in the lower mantle beneath the central-Pacific. SKS, SPdKS, and SKKS data for the generally faster-than-average circum-Pacific lower mantle are well-fit by models lacking any such low-velocity boundary layer. The slow boundary layer beneath the central Pacific may be a localized zone of partial melt, or perhaps a chemically distinct layer, with its location linked to overlying upwelling motions.

Original languageEnglish (US)
JournalGeophysical Research Letters
Volume23
Issue number9
StatePublished - May 1 1996
Externally publishedYes

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lower mantle
boundary layers
Earth mantle
boundary layer
mantle
mantle structure
low speed
upwelling
melt
upwelling water
earthquake
arrivals
earthquakes
recording
detection

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

Seismic detection of a thin laterally varying boundary layer at the base of the mantle beneath the central-Pacific. / Garnero, Edward; Helmberger, Donald V.

In: Geophysical Research Letters, Vol. 23, No. 9, 01.05.1996.

Research output: Contribution to journalArticle

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