Ultralow Velocity Zone Locations: A Global Assessment

Shule Yu, Edward Garnero

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

We have compiled all previous ultralow velocity zone (ULVZ) studies, and digitized their core-mantle boundary (CMB) sampling locations. For studies that presented sampling locations based on infinite frequency ray theory, we approximated Fresnel zones onto a 0.5° × 0.5° grid. Results for these studies were separated according to wave type: (1) core-reflected phases, which have a single location of ULVZ sampling (ScS, ScP, PcP), (2) core waves that can sample ULVZs at the core entrance and exit locations of the wave (e.g., SPdKS, PKKP, and PKP), and (3) waves which have uncertainties of ULVZ location due to long CMB sampling paths, e.g., diffracted energy sampling over a broad region (Pdiff, Sdiff). For studies that presented specific modeled ULVZ geographical shapes or PKP scatter probability maps, we digitized the regions. We present summary maps of the ULVZ coverage, as well as published locations arguing against ULVZ presence. A key finding is that there is not a simple mapping between lowermost mantle reduced tomographic velocities and observed ULVZ locations, especially given the presence of ULVZs outside of lowermost mantle large low velocity provinces (LLVPs). Significant location uncertainty exists for some of the ULVZ imaging wave types. Nonetheless, this compilation supports a compositionally distinct origin for at least some ULVZs. ULVZs are more likely to be found near LLVP boundaries, however, their relationship to overlying surface locations of hot spots are less obvious. The new digital ULVZ database is freely available for download.

Original languageEnglish (US)
Pages (from-to)396-414
Number of pages19
JournalGeochemistry, Geophysics, Geosystems
Volume19
Issue number2
DOIs
StatePublished - Feb 1 2018

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sampling
Sampling
core-mantle boundary
low speed
Earth mantle
mantle
entrances
rays
grids
Imaging techniques
energy
province
Uncertainty

Keywords

  • CMB
  • LLSVP
  • LLVP
  • partial melt
  • ultralow velocity zone
  • ULVZ

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

Cite this

Ultralow Velocity Zone Locations : A Global Assessment. / Yu, Shule; Garnero, Edward.

In: Geochemistry, Geophysics, Geosystems, Vol. 19, No. 2, 01.02.2018, p. 396-414.

Research output: Contribution to journalArticle

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