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Title: Geographic variations in lowermost mantle structure from the ray parameters and decay constants of core-diffracted waves: CMBR Structure From P diff and S diff

Abstract

We propose an array-based approach for constraining seismic velocity structure in the lowermost mantle by measuring the frequency dependence of the ray parameter p and decay constant γ for core-diffracted waves (P diff and SH diff). The approach uses an iterative multichannel cross-correlation algorithm that solves for relative arrival times and amplitudes of core-diffracted waveforms from multiple peaks in normalized correlograms from pairs of coazimuthal stations. The approach is applied to 60 m b ≥ 5.8 earthquakes for P diff and 36 for SH diff during 2001–2002, with nearly 50,000 unique profile station pairs with epicentral-distance differences of Δd ≥ 10° and azimuth differences of Δφ ≤ 10°, sampling a significant portion of the lowermost mantle. Cap-averaging the resulting ray parameter estimates produces geographic variations that are largely consistent with the distribution of lowermost mantle large low-velocity provinces and seismically fast slab-accumulation regions seen in seismic tomography models, whose locations also greatly influence the geographic distribution of heat flow out of the core. Geographic variations in station-pair diffracted-wave decay constants differ from those of the ray parameters, suggesting that variations in the decay of core-diffracted waves are more linked to lowermost mantle seismic velocity gradients than absolute values of seismicmore » velocity. The ray parameters and decay constants of core-diffracted waves are strongly frequency-dependent, and these frequency variations also vary significantly with geographic location. Combining lateral and vertical seismic-velocity variations with mineral-physics data on elasticity and conductivity of lowermost mantle species can provide constraints on D" composition and CMB heat flux.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Washington Univ., St. Louis, MO (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1507323
Report Number(s):
LA-UR-16-29251
Journal ID: ISSN 2169-9313
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Solid Earth
Additional Journal Information:
Journal Volume: 122; Journal Issue: 7; Journal ID: ISSN 2169-9313
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; core‐diffracted waves; core‐mantle boundary; Pdiff and Sdiff dispersion; Pdiff and Sdiff amplitude decay; CMB velocity structure

Citation Formats

Euler, Garrett G., and Wysession, Michael E. Geographic variations in lowermost mantle structure from the ray parameters and decay constants of core-diffracted waves: CMBR Structure From P diff and S diff. United States: N. p., 2017. Web. doi:10.1002/2017JB013930.
Euler, Garrett G., & Wysession, Michael E. Geographic variations in lowermost mantle structure from the ray parameters and decay constants of core-diffracted waves: CMBR Structure From P diff and S diff. United States. doi:10.1002/2017JB013930.
Euler, Garrett G., and Wysession, Michael E. Tue . "Geographic variations in lowermost mantle structure from the ray parameters and decay constants of core-diffracted waves: CMBR Structure From P diff and S diff". United States. doi:10.1002/2017JB013930. https://www.osti.gov/servlets/purl/1507323.
@article{osti_1507323,
title = {Geographic variations in lowermost mantle structure from the ray parameters and decay constants of core-diffracted waves: CMBR Structure From P diff and S diff},
author = {Euler, Garrett G. and Wysession, Michael E.},
abstractNote = {We propose an array-based approach for constraining seismic velocity structure in the lowermost mantle by measuring the frequency dependence of the ray parameter p and decay constant γ for core-diffracted waves (Pdiff and SHdiff). The approach uses an iterative multichannel cross-correlation algorithm that solves for relative arrival times and amplitudes of core-diffracted waveforms from multiple peaks in normalized correlograms from pairs of coazimuthal stations. The approach is applied to 60 mb ≥ 5.8 earthquakes for Pdiff and 36 for SHdiff during 2001–2002, with nearly 50,000 unique profile station pairs with epicentral-distance differences of Δd ≥ 10° and azimuth differences of Δφ ≤ 10°, sampling a significant portion of the lowermost mantle. Cap-averaging the resulting ray parameter estimates produces geographic variations that are largely consistent with the distribution of lowermost mantle large low-velocity provinces and seismically fast slab-accumulation regions seen in seismic tomography models, whose locations also greatly influence the geographic distribution of heat flow out of the core. Geographic variations in station-pair diffracted-wave decay constants differ from those of the ray parameters, suggesting that variations in the decay of core-diffracted waves are more linked to lowermost mantle seismic velocity gradients than absolute values of seismic velocity. The ray parameters and decay constants of core-diffracted waves are strongly frequency-dependent, and these frequency variations also vary significantly with geographic location. Combining lateral and vertical seismic-velocity variations with mineral-physics data on elasticity and conductivity of lowermost mantle species can provide constraints on D" composition and CMB heat flux.},
doi = {10.1002/2017JB013930},
journal = {Journal of Geophysical Research. Solid Earth},
number = 7,
volume = 122,
place = {United States},
year = {2017},
month = {8}
}

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