Upper Mantle Earth Structure in Africa From Full-Wave Ambient Noise Tomography

E. L. Emry, Y. Shen, A. A. Nyblade, A. Flinders, X. Bao

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Our understanding of the tectonic development of the African continent and the interplay between its geological provinces is hindered by unevenly distributed seismic instrumentation. In order to better understand the continent, we used long-period ambient noise full-waveform tomography on data collected from 186 broadband seismic stations throughout Africa and surrounding regions to better image the upper mantle structure. We extracted empirical Green's functions from ambient seismic noise using a frequency-time normalization method and retrieved coherent signal at periods of 7–340 s. We simulated wave propagation through a heterogeneous Earth using a spherical finite-difference approach to obtain synthetic waveforms, measured the misfit as phase delay between the data and synthetics, calculated numerical sensitivity kernels using the scattering integral approach, and iteratively inverted for structure. The resulting images of isotropic, shear wave speed for the continent reveal segmented, low-velocity upper mantle beneath the highly magmatic northern and eastern sections of the East African Rift System (EARS). In the southern and western sections, high-velocity upper mantle dominates, and distinct, low-velocity anomalies are restricted to regions of current volcanism. At deeper depths, the southern and western EARS transition to low velocities. In addition to the EARS, several low-velocity anomalies are scattered through the shallow upper mantle beneath Angola and North Africa, and some of these low-velocity anomalies may be connected to a deeper feature. Distinct upper mantle high-velocity anomalies are imaged throughout the continent and suggest multiple cratonic roots within the Congo region and possible cratonic roots within the Sahara Metacraton.

Original languageEnglish (US)
Pages (from-to)120-147
Number of pages28
JournalGeochemistry, Geophysics, Geosystems
Volume20
Issue number1
DOIs
StatePublished - Jan 2019

Fingerprint

Earth structure
ambient noise
African rift system
low speed
tomography
Tomography
upper mantle
continents
Earth mantle
Earth (planet)
anomalies
anomaly
waveforms
Angola
seismic noise
S waves
tectonics
wave propagation
mantle structure
Shear waves

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Cite this

Emry, E. L. ; Shen, Y. ; Nyblade, A. A. ; Flinders, A. ; Bao, X. / Upper Mantle Earth Structure in Africa From Full-Wave Ambient Noise Tomography. In: Geochemistry, Geophysics, Geosystems. 2019 ; Vol. 20, No. 1. pp. 120-147.
@article{85bddb05fe8448dc933efed69fe52d22,
title = "Upper Mantle Earth Structure in Africa From Full-Wave Ambient Noise Tomography",
abstract = "Our understanding of the tectonic development of the African continent and the interplay between its geological provinces is hindered by unevenly distributed seismic instrumentation. In order to better understand the continent, we used long-period ambient noise full-waveform tomography on data collected from 186 broadband seismic stations throughout Africa and surrounding regions to better image the upper mantle structure. We extracted empirical Green's functions from ambient seismic noise using a frequency-time normalization method and retrieved coherent signal at periods of 7–340 s. We simulated wave propagation through a heterogeneous Earth using a spherical finite-difference approach to obtain synthetic waveforms, measured the misfit as phase delay between the data and synthetics, calculated numerical sensitivity kernels using the scattering integral approach, and iteratively inverted for structure. The resulting images of isotropic, shear wave speed for the continent reveal segmented, low-velocity upper mantle beneath the highly magmatic northern and eastern sections of the East African Rift System (EARS). In the southern and western sections, high-velocity upper mantle dominates, and distinct, low-velocity anomalies are restricted to regions of current volcanism. At deeper depths, the southern and western EARS transition to low velocities. In addition to the EARS, several low-velocity anomalies are scattered through the shallow upper mantle beneath Angola and North Africa, and some of these low-velocity anomalies may be connected to a deeper feature. Distinct upper mantle high-velocity anomalies are imaged throughout the continent and suggest multiple cratonic roots within the Congo region and possible cratonic roots within the Sahara Metacraton.",
author = "Emry, {E. L.} and Y. Shen and Nyblade, {A. A.} and A. Flinders and X. Bao",
year = "2019",
month = "1",
doi = "10.1029/2018GC007804",
language = "English (US)",
volume = "20",
pages = "120--147",
journal = "Geochemistry, Geophysics, Geosystems",
issn = "1525-2027",
publisher = "American Geophysical Union",
number = "1",

}

Upper Mantle Earth Structure in Africa From Full-Wave Ambient Noise Tomography. / Emry, E. L.; Shen, Y.; Nyblade, A. A.; Flinders, A.; Bao, X.

In: Geochemistry, Geophysics, Geosystems, Vol. 20, No. 1, 01.2019, p. 120-147.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Upper Mantle Earth Structure in Africa From Full-Wave Ambient Noise Tomography

AU - Emry, E. L.

AU - Shen, Y.

AU - Nyblade, A. A.

AU - Flinders, A.

AU - Bao, X.

PY - 2019/1

Y1 - 2019/1

N2 - Our understanding of the tectonic development of the African continent and the interplay between its geological provinces is hindered by unevenly distributed seismic instrumentation. In order to better understand the continent, we used long-period ambient noise full-waveform tomography on data collected from 186 broadband seismic stations throughout Africa and surrounding regions to better image the upper mantle structure. We extracted empirical Green's functions from ambient seismic noise using a frequency-time normalization method and retrieved coherent signal at periods of 7–340 s. We simulated wave propagation through a heterogeneous Earth using a spherical finite-difference approach to obtain synthetic waveforms, measured the misfit as phase delay between the data and synthetics, calculated numerical sensitivity kernels using the scattering integral approach, and iteratively inverted for structure. The resulting images of isotropic, shear wave speed for the continent reveal segmented, low-velocity upper mantle beneath the highly magmatic northern and eastern sections of the East African Rift System (EARS). In the southern and western sections, high-velocity upper mantle dominates, and distinct, low-velocity anomalies are restricted to regions of current volcanism. At deeper depths, the southern and western EARS transition to low velocities. In addition to the EARS, several low-velocity anomalies are scattered through the shallow upper mantle beneath Angola and North Africa, and some of these low-velocity anomalies may be connected to a deeper feature. Distinct upper mantle high-velocity anomalies are imaged throughout the continent and suggest multiple cratonic roots within the Congo region and possible cratonic roots within the Sahara Metacraton.

AB - Our understanding of the tectonic development of the African continent and the interplay between its geological provinces is hindered by unevenly distributed seismic instrumentation. In order to better understand the continent, we used long-period ambient noise full-waveform tomography on data collected from 186 broadband seismic stations throughout Africa and surrounding regions to better image the upper mantle structure. We extracted empirical Green's functions from ambient seismic noise using a frequency-time normalization method and retrieved coherent signal at periods of 7–340 s. We simulated wave propagation through a heterogeneous Earth using a spherical finite-difference approach to obtain synthetic waveforms, measured the misfit as phase delay between the data and synthetics, calculated numerical sensitivity kernels using the scattering integral approach, and iteratively inverted for structure. The resulting images of isotropic, shear wave speed for the continent reveal segmented, low-velocity upper mantle beneath the highly magmatic northern and eastern sections of the East African Rift System (EARS). In the southern and western sections, high-velocity upper mantle dominates, and distinct, low-velocity anomalies are restricted to regions of current volcanism. At deeper depths, the southern and western EARS transition to low velocities. In addition to the EARS, several low-velocity anomalies are scattered through the shallow upper mantle beneath Angola and North Africa, and some of these low-velocity anomalies may be connected to a deeper feature. Distinct upper mantle high-velocity anomalies are imaged throughout the continent and suggest multiple cratonic roots within the Congo region and possible cratonic roots within the Sahara Metacraton.

UR - http://www.scopus.com/inward/record.url?scp=85059511101&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85059511101&partnerID=8YFLogxK

U2 - 10.1029/2018GC007804

DO - 10.1029/2018GC007804

M3 - Article

AN - SCOPUS:85059511101

VL - 20

SP - 120

EP - 147

JO - Geochemistry, Geophysics, Geosystems

JF - Geochemistry, Geophysics, Geosystems

SN - 1525-2027

IS - 1

ER -