On the absence of an ultralow-velocity zone in the north Pacific

Sebastian Rost, Edward Garnero, Michael S. Thorne, Alexander R. Hutko

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

[1] Using an unusually large earthquake near the big island of Hawaii, we study the core mantle boundary (CMB) beneath the north-northeastern Pacific between Hawaii and North America. A dense sampling of the CMB is achieved using the core-reflected phase PcP recorded at a large number of high-quality stations in North America, including networks in California, Oregon, Washington, and Alaska, as well as at EarthScope's USArray stations. We apply an adaptive stacking technique for optimal record alignment on specific phases (namely P and PcP) and subsequently stack seismograms to obtain summation traces possessing relatively high signal-to-noise ratios of PcP and P. Anomalous ultralow-velocity zone (ULVZ) layering at the CMB has been noted to exist in various parts of the Pacific beneath the lowermost mantle large low shear velocity province imaged by tomography. ULVZ structure produces anomalous PcP waveform variations in the form of precursors to PcP. These PcP data, however, lack precursory energy, indicating either that (1) ULVZ layering is lacking or (2) that a ULVZ is present and thinner than our detection threshold, i.e., less than a few kilometers thick. We use synthetic waveform modeling to establish the sensitivity and utility of investigating the time window ahead of PcP for precursors generated from fine-scale CMB layering. These results, combined with evidence for ULVZ structure in other parts of the Pacific, suggest that ULVZs are intermittent and possibly only detectable in regions where mantle currents collect ULVZ material, whether or not partially molten, presumably beneath (or near) upwellings or plumes.

Original languageEnglish (US)
Article numberB04312
JournalJournal of Geophysical Research: Solid Earth
Volume115
Issue number4
DOIs
StatePublished - 2010

Fingerprint

core-mantle boundary
waveforms
Earth mantle
stations
mantle
seismograms
upwelling water
seismogram
stacking
signal-to-noise ratio
tomography
plumes
Tomography
Molten materials
Earthquakes
Signal to noise ratio
upwelling
signal to noise ratios
earthquakes
plume

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

On the absence of an ultralow-velocity zone in the north Pacific. / Rost, Sebastian; Garnero, Edward; Thorne, Michael S.; Hutko, Alexander R.

In: Journal of Geophysical Research: Solid Earth, Vol. 115, No. 4, B04312, 2010.

Research output: Contribution to journalArticle

Rost, Sebastian ; Garnero, Edward ; Thorne, Michael S. ; Hutko, Alexander R. / On the absence of an ultralow-velocity zone in the north Pacific. In: Journal of Geophysical Research: Solid Earth. 2010 ; Vol. 115, No. 4.
@article{c3d3a2f144a04d46a81d0801e3a3dd0d,
title = "On the absence of an ultralow-velocity zone in the north Pacific",
abstract = "[1] Using an unusually large earthquake near the big island of Hawaii, we study the core mantle boundary (CMB) beneath the north-northeastern Pacific between Hawaii and North America. A dense sampling of the CMB is achieved using the core-reflected phase PcP recorded at a large number of high-quality stations in North America, including networks in California, Oregon, Washington, and Alaska, as well as at EarthScope's USArray stations. We apply an adaptive stacking technique for optimal record alignment on specific phases (namely P and PcP) and subsequently stack seismograms to obtain summation traces possessing relatively high signal-to-noise ratios of PcP and P. Anomalous ultralow-velocity zone (ULVZ) layering at the CMB has been noted to exist in various parts of the Pacific beneath the lowermost mantle large low shear velocity province imaged by tomography. ULVZ structure produces anomalous PcP waveform variations in the form of precursors to PcP. These PcP data, however, lack precursory energy, indicating either that (1) ULVZ layering is lacking or (2) that a ULVZ is present and thinner than our detection threshold, i.e., less than a few kilometers thick. We use synthetic waveform modeling to establish the sensitivity and utility of investigating the time window ahead of PcP for precursors generated from fine-scale CMB layering. These results, combined with evidence for ULVZ structure in other parts of the Pacific, suggest that ULVZs are intermittent and possibly only detectable in regions where mantle currents collect ULVZ material, whether or not partially molten, presumably beneath (or near) upwellings or plumes.",
author = "Sebastian Rost and Edward Garnero and Thorne, {Michael S.} and Hutko, {Alexander R.}",
year = "2010",
doi = "10.1029/2009JB006420",
language = "English (US)",
volume = "115",
journal = "Journal of Geophysical Research: Atmospheres",
issn = "2169-897X",
publisher = "Wiley-Blackwell",
number = "4",

}

TY - JOUR

T1 - On the absence of an ultralow-velocity zone in the north Pacific

AU - Rost, Sebastian

AU - Garnero, Edward

AU - Thorne, Michael S.

AU - Hutko, Alexander R.

PY - 2010

Y1 - 2010

N2 - [1] Using an unusually large earthquake near the big island of Hawaii, we study the core mantle boundary (CMB) beneath the north-northeastern Pacific between Hawaii and North America. A dense sampling of the CMB is achieved using the core-reflected phase PcP recorded at a large number of high-quality stations in North America, including networks in California, Oregon, Washington, and Alaska, as well as at EarthScope's USArray stations. We apply an adaptive stacking technique for optimal record alignment on specific phases (namely P and PcP) and subsequently stack seismograms to obtain summation traces possessing relatively high signal-to-noise ratios of PcP and P. Anomalous ultralow-velocity zone (ULVZ) layering at the CMB has been noted to exist in various parts of the Pacific beneath the lowermost mantle large low shear velocity province imaged by tomography. ULVZ structure produces anomalous PcP waveform variations in the form of precursors to PcP. These PcP data, however, lack precursory energy, indicating either that (1) ULVZ layering is lacking or (2) that a ULVZ is present and thinner than our detection threshold, i.e., less than a few kilometers thick. We use synthetic waveform modeling to establish the sensitivity and utility of investigating the time window ahead of PcP for precursors generated from fine-scale CMB layering. These results, combined with evidence for ULVZ structure in other parts of the Pacific, suggest that ULVZs are intermittent and possibly only detectable in regions where mantle currents collect ULVZ material, whether or not partially molten, presumably beneath (or near) upwellings or plumes.

AB - [1] Using an unusually large earthquake near the big island of Hawaii, we study the core mantle boundary (CMB) beneath the north-northeastern Pacific between Hawaii and North America. A dense sampling of the CMB is achieved using the core-reflected phase PcP recorded at a large number of high-quality stations in North America, including networks in California, Oregon, Washington, and Alaska, as well as at EarthScope's USArray stations. We apply an adaptive stacking technique for optimal record alignment on specific phases (namely P and PcP) and subsequently stack seismograms to obtain summation traces possessing relatively high signal-to-noise ratios of PcP and P. Anomalous ultralow-velocity zone (ULVZ) layering at the CMB has been noted to exist in various parts of the Pacific beneath the lowermost mantle large low shear velocity province imaged by tomography. ULVZ structure produces anomalous PcP waveform variations in the form of precursors to PcP. These PcP data, however, lack precursory energy, indicating either that (1) ULVZ layering is lacking or (2) that a ULVZ is present and thinner than our detection threshold, i.e., less than a few kilometers thick. We use synthetic waveform modeling to establish the sensitivity and utility of investigating the time window ahead of PcP for precursors generated from fine-scale CMB layering. These results, combined with evidence for ULVZ structure in other parts of the Pacific, suggest that ULVZs are intermittent and possibly only detectable in regions where mantle currents collect ULVZ material, whether or not partially molten, presumably beneath (or near) upwellings or plumes.

UR - http://www.scopus.com/inward/record.url?scp=77954351072&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77954351072&partnerID=8YFLogxK

U2 - 10.1029/2009JB006420

DO - 10.1029/2009JB006420

M3 - Article

AN - SCOPUS:77954351072

VL - 115

JO - Journal of Geophysical Research: Atmospheres

JF - Journal of Geophysical Research: Atmospheres

SN - 2169-897X

IS - 4

M1 - B04312

ER -