Oceanic lithosphere-asthenosphere boundary from surface wave dispersion data

Research areas:

Environnement, Paléo-Environnement et Bio-Indicateurs (2011 - 2016)

Year:

2014

Authors:

G. Burgos
J-P. Montagner
Éric Beucler
Yann Capdeville
Antoine Mocquet

Journal:

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH

Volume:

119

Number:

Pages:

1079-1093

Month:

February

ISSN:

2169-9313

BibTex:

@article{WOS:000333034600018,
author = "G. Burgos and J-P. Montagner and {\'E}ric Beucler and Yann Capdeville and Antoine Mocquet",
abstract = "According to different types of observations, the nature of
   lithosphere-asthenosphere boundary (LAB) is controversial. Using a
   massive data set of surface wave dispersions in a broad period range
   (15-300 s), we have developed a three-dimensional upper mantle
   tomographic model (first-order perturbation theory) at the global scale.
   This is used to derive maps of the LAB from the resolved elastic
   parameters. The key effects of shallow layers and anisotropy are taken
   into account in the inversion process. We investigate LAB distribution
   primarily below the oceans, according to different kinds of proxies that
   correspond to the base of the lithosphere from the shear velocity
   variation at depth, the amplitude radial anisotropy, and the changes in
   azimuthal anisotropy G orientation. The estimations of the LAB depth
   based on the shear velocity increase from a thin lithosphere
   (approximate to 20 km) in the ridges, to a thick old-ocean lithosphere
   (approximate to 120-130 km). The radial anisotropy proxy shows a very
   fast increase in the LAB depth from the ridges, from approximate to 50
   km to the older ocean where it reaches a remarkable monotonic
   subhorizontal profile (approximate to 70-80 km). The LAB depths inferred
   from the azimuthal anisotropy proxy show deeper values for the
   increasing oceanic lithosphere (approximate to 130-135 km). The
   difference between the evolution of the LAB depth with the age of the
   oceanic lithosphere computed from the shear velocity and azimuthal
   anisotropy proxies and from the radial anisotropy proxy raises questions
   about the nature of the LAB in the oceanic regions and of the formation
   of the oceanic plates.",
doi = "10.1002/2013JB010528",
extra = "PICL",
issn = "2169-9313",
journal = "JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH",
month = "FEB",
number = "2",
pages = "1079-1093",
title = "{O}ceanic lithosphere-asthenosphere boundary from surface wave dispersion   data",
volume = "119",
year = "2014",
}

Abstract:

According to different types of observations, the nature of
lithosphere-asthenosphere boundary (LAB) is controversial. Using a
massive data set of surface wave dispersions in a broad period range
(15-300 s), we have developed a three-dimensional upper mantle
tomographic model (first-order perturbation theory) at the global scale.
This is used to derive maps of the LAB from the resolved elastic
parameters. The key effects of shallow layers and anisotropy are taken
into account in the inversion process. We investigate LAB distribution
primarily below the oceans, according to different kinds of proxies that
correspond to the base of the lithosphere from the shear velocity
variation at depth, the amplitude radial anisotropy, and the changes in
azimuthal anisotropy G orientation. The estimations of the LAB depth
based on the shear velocity increase from a thin lithosphere
(approximate to 20 km) in the ridges, to a thick old-ocean lithosphere
(approximate to 120-130 km). The radial anisotropy proxy shows a very
fast increase in the LAB depth from the ridges, from approximate to 50
km to the older ocean where it reaches a remarkable monotonic
subhorizontal profile (approximate to 70-80 km). The LAB depths inferred
from the azimuthal anisotropy proxy show deeper values for the
increasing oceanic lithosphere (approximate to 130-135 km). The
difference between the evolution of the LAB depth with the age of the
oceanic lithosphere computed from the shear velocity and azimuthal
anisotropy proxies and from the radial anisotropy proxy raises questions
about the nature of the LAB in the oceanic regions and of the formation
of the oceanic plates.