Azimuthal anisotropy of Rayleigh-wave phase velocities in the east-central United States.

Deschamps, F., Lebedev, S., Meier, T. and Trampert, J. (2008) Azimuthal anisotropy of Rayleigh-wave phase velocities in the east-central United States. Geophysical Journal International, 173 (3). pp. 827-843. DOI 10.1111/j.1365-246X.2008.03751.x.

Full text not available from this repository.

Supplementary data:

Abstract

We explore the Rayleigh-wave phase velocity structure of the east-central US in a broad period range (10–200 s). Using a recent implementation of the two-stations method, we first measure interstation dispersion curves of Rayleigh-wave phase velocities along 60 paths. We then invert our collection of dispersion curves for isotropic and azimuthally anisotropic (2Ψ and 4Ψ) phase–velocity maps. The inversion is performed by a damped, smoothed LSQR, and the output model is parametrized on a triangular grid of knots with a 140 km grid spacing. Using the isotropic component of the phase velocity maps to constrain regional variations in shear velocity and Moho-depth, we observe that over the upper-middle crust depth range (z < 30 km) shear wave velocities are lower beneath the Grenville and Appalachian orogenic provinces than beneath the Central Plains to the west. The amplitude of (2Ψ) anisotropy and the azimuth of the fast-propagation direction at periods between 20 and 34 s vary laterally. Beneath the Grenville and Appalachian provinces, the amplitude of anisotropy reaches 1 per cent of the average phase velocity, and the azimuth of the fast-propagation direction is uniform and equal to 32°. West of the Grenville front, the average amplitude falls to 0.5 per cent, and the azimuth of the fast-propagation direction is less uniform. In the period range 45–60 s, anisotropy is smaller in amplitude (∼0.5 per cent) and with a regionally uniform azimuth of the fast-propagation direction of around 165°. Around 140 s, the amplitude of 2Ψ anisotropy is larger again (>1 per cent), and the azimuth of the fast-propagation direction is uniform over the entire region and equal to 54°. Our results suggest that azimuthal anisotropy beneath the east-central US is vertically distributed in three distinct layers, with a different geodynamic origin for each of them.

Document Type: Article
Keywords: Surface waves and free oscillations, Seismic anisotropy, North America
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R06
OceanRep > The Future Ocean - Cluster of Excellence > FO-R09
OceanRep > The Future Ocean - Cluster of Excellence
Kiel University
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1111/j.1365-246X.2008.03751.x
ISSN: 0956-540X
Projects: Future Ocean
Date Deposited: 05 Oct 2017 09:49
Last Modified: 28 Mar 2019 11:16
URI: http://oceanrep.geomar.de/id/eprint/39659

Actions (login required)

View Item View Item