Preliminary evidence for a lower mantle shear wave velocity discontinuity beneath the central Pacific

Edward Garnero, D. V. Helmberger, S. Grand

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

In a dataset consisting of long-period waveforms (5-20 s) and differential travel times of S, ScS, and the arrival from the D″ layer, Scd, evidence is found for a laterally varying shear wave velocity (VS) discontinuity at the base of the mantle. Two different localized D″ regions beneath the central Pacific have been investigated. Predictions from a model having a VS discontinuity 180 km above the core-mantle boundary (CMB) agree well with observations for an eastern mid-Pacific CMB region. This thickness differs from VS discontinuity thicknesses found in other regions, which average near 280 km. The data presented here from a western mid-Pacific CMB region are more complicated, and are difficult to fit with a one-dimensional (1-D) structure. Some of the data from the western region show evidence for a thicker D″ layer (approximately 280 km), though this finding is poorly constrained. Our data do not resolve the 'sharpness' of the VS jump at the top of D″, i.e. the depth range over which the VS increase occurs, and in fact may be modeled equally well by a lower mantle with the increase in VS at the top of D″ occurring over a 100 km depth range. The Scd-S and ScS-S differential travel times were corrected for a published 3-D mantle model, to study upper and middle mantle heterogeneity effects on these times.

Original languageEnglish (US)
Pages (from-to)335-347
Number of pages13
JournalPhysics of the Earth and Planetary Interiors
Volume79
Issue number3-4
DOIs
StatePublished - 1993
Externally publishedYes

Fingerprint

lower mantle
core-mantle boundary
D region
S waves
wave velocity
S-wave
discontinuity
Earth mantle
travel
mantle
travel time
sharpness
arrivals
waveforms
predictions
prediction

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science
  • Physics and Astronomy (miscellaneous)
  • Astronomy and Astrophysics
  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Cite this

Preliminary evidence for a lower mantle shear wave velocity discontinuity beneath the central Pacific. / Garnero, Edward; Helmberger, D. V.; Grand, S.

In: Physics of the Earth and Planetary Interiors, Vol. 79, No. 3-4, 1993, p. 335-347.

Research output: Contribution to journalArticle

@article{607cd54bb6754d29b5198d65af51c4a8,
title = "Preliminary evidence for a lower mantle shear wave velocity discontinuity beneath the central Pacific",
abstract = "In a dataset consisting of long-period waveforms (5-20 s) and differential travel times of S, ScS, and the arrival from the D″ layer, Scd, evidence is found for a laterally varying shear wave velocity (VS) discontinuity at the base of the mantle. Two different localized D″ regions beneath the central Pacific have been investigated. Predictions from a model having a VS discontinuity 180 km above the core-mantle boundary (CMB) agree well with observations for an eastern mid-Pacific CMB region. This thickness differs from VS discontinuity thicknesses found in other regions, which average near 280 km. The data presented here from a western mid-Pacific CMB region are more complicated, and are difficult to fit with a one-dimensional (1-D) structure. Some of the data from the western region show evidence for a thicker D″ layer (approximately 280 km), though this finding is poorly constrained. Our data do not resolve the 'sharpness' of the VS jump at the top of D″, i.e. the depth range over which the VS increase occurs, and in fact may be modeled equally well by a lower mantle with the increase in VS at the top of D″ occurring over a 100 km depth range. The Scd-S and ScS-S differential travel times were corrected for a published 3-D mantle model, to study upper and middle mantle heterogeneity effects on these times.",
author = "Edward Garnero and Helmberger, {D. V.} and S. Grand",
year = "1993",
doi = "10.1016/0031-9201(93)90113-N",
language = "English (US)",
volume = "79",
pages = "335--347",
journal = "Physics of the Earth and Planetary Interiors",
issn = "0031-9201",
publisher = "Elsevier",
number = "3-4",

}

TY - JOUR

T1 - Preliminary evidence for a lower mantle shear wave velocity discontinuity beneath the central Pacific

AU - Garnero, Edward

AU - Helmberger, D. V.

AU - Grand, S.

PY - 1993

Y1 - 1993

N2 - In a dataset consisting of long-period waveforms (5-20 s) and differential travel times of S, ScS, and the arrival from the D″ layer, Scd, evidence is found for a laterally varying shear wave velocity (VS) discontinuity at the base of the mantle. Two different localized D″ regions beneath the central Pacific have been investigated. Predictions from a model having a VS discontinuity 180 km above the core-mantle boundary (CMB) agree well with observations for an eastern mid-Pacific CMB region. This thickness differs from VS discontinuity thicknesses found in other regions, which average near 280 km. The data presented here from a western mid-Pacific CMB region are more complicated, and are difficult to fit with a one-dimensional (1-D) structure. Some of the data from the western region show evidence for a thicker D″ layer (approximately 280 km), though this finding is poorly constrained. Our data do not resolve the 'sharpness' of the VS jump at the top of D″, i.e. the depth range over which the VS increase occurs, and in fact may be modeled equally well by a lower mantle with the increase in VS at the top of D″ occurring over a 100 km depth range. The Scd-S and ScS-S differential travel times were corrected for a published 3-D mantle model, to study upper and middle mantle heterogeneity effects on these times.

AB - In a dataset consisting of long-period waveforms (5-20 s) and differential travel times of S, ScS, and the arrival from the D″ layer, Scd, evidence is found for a laterally varying shear wave velocity (VS) discontinuity at the base of the mantle. Two different localized D″ regions beneath the central Pacific have been investigated. Predictions from a model having a VS discontinuity 180 km above the core-mantle boundary (CMB) agree well with observations for an eastern mid-Pacific CMB region. This thickness differs from VS discontinuity thicknesses found in other regions, which average near 280 km. The data presented here from a western mid-Pacific CMB region are more complicated, and are difficult to fit with a one-dimensional (1-D) structure. Some of the data from the western region show evidence for a thicker D″ layer (approximately 280 km), though this finding is poorly constrained. Our data do not resolve the 'sharpness' of the VS jump at the top of D″, i.e. the depth range over which the VS increase occurs, and in fact may be modeled equally well by a lower mantle with the increase in VS at the top of D″ occurring over a 100 km depth range. The Scd-S and ScS-S differential travel times were corrected for a published 3-D mantle model, to study upper and middle mantle heterogeneity effects on these times.

UR - http://www.scopus.com/inward/record.url?scp=0027801694&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0027801694&partnerID=8YFLogxK

U2 - 10.1016/0031-9201(93)90113-N

DO - 10.1016/0031-9201(93)90113-N

M3 - Article

VL - 79

SP - 335

EP - 347

JO - Physics of the Earth and Planetary Interiors

JF - Physics of the Earth and Planetary Interiors

SN - 0031-9201

IS - 3-4

ER -