Journal
COMPTES RENDUS GEOSCIENCE
Volume 343, Issue 8-9, Pages 571-583Publisher
ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
DOI: 10.1016/j.crte.2011.04.004
Keywords
East Pacific Rise; Lithosphere; Oceanic Uppermost Mantle; Low-velocity zone; Ambient noise; Fundamental; and higher-mode Scholte-Rayleigh waves
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Funding
- US National Science Foundation [OCE-0242117]
- W.M. Keck Foundation
- Shell at MIT on passive seismic imaging
- Institute of Geophysics and Planetary Physics, Scripps Institute of Oceanography, UCSD
- Division Of Ocean Sciences
- Directorate For Geosciences [1232725] Funding Source: National Science Foundation
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Inter-station Green's functions estimated from ambient noise studies have been widely used to investigate crustal structure. However, most studies are restricted to continental areas and use fundamental-mode surface waves only. In this study, we recover inter-station surface (Scholte-Rayleigh) wave empirical Green's function (EGFs) of both the fundamental- and the first-higher mode using one year of continuous seismic noise records on the vertical component from 28 ocean bottom seismographs deployed in the Quebrada/Discovery/Gofar transform faults region on the East Pacific Rise. The average phase-velocity dispersion of the fundamental mode (period band 2-30 s) and the first-higher mode (period band 3-7 s) from all EGFs are used to invert for the 1-D average, shear-velocity structure in the crust and uppermost mantle using a model-space search algorithm. The preferred shear-velocity models reveal low velocities (4.29 km/s) between Moho and 25 km depth below sea-surface, suggesting the absence of a fast uppermost mantle lid in this young (0-2 Myr) oceanic region. An even more pronounced low-velocity zone, with shear velocities similar to 3.85 km/s, appears at a depth between 25-40 km below sea-surface. Along with previous results, our study indicates that the shear velocity in the uppermost oceanic mantle increases with increasing seafloor age, consistent with age-related lithospheric cooling. (C) 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
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