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Constraints on D″ beneath the North Atlantic region from P and S traveltimes and amplitudes

Durand, S. and Thomas, C. and Jackson, J. M. (2019) Constraints on D″ beneath the North Atlantic region from P and S traveltimes and amplitudes. Geophysical Journal International, 216 (2). pp. 1132-1144. ISSN 0956-540X. http://resolver.caltech.edu/CaltechAUTHORS:20181211-125022062

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Abstract

In this study, we discuss possible origins of the D″ reflector beneath the North Atlantic region based on a combined analysis of P and S wave data. We use over 700 USArray station recordings of the M_w 6.3 earthquake that occurred in April 2010 in Spain. In order to investigate the D″ layer we look for waves reflected off the top of it, namely PdP and SdS waves, and compare them to the core–mantle boundary (CMB) reflections used as reference phases. The differences in traveltimes and amplitudes are sensitive to D″ properties. Because the USArray installation generates a dense array, we are able to provide an almost continuous map of the detection or absence of PdP and SdS waves in the North Atlantic region. We use a Bayesian inversion for traveltimes, together with synthetic seismogram calculations, to find the best-fitting D″ properties, (Vp, Vs) jumps across the D″ interface and D″ thickness. We find that the best-fitting models are for a D″ layer of about 300 km thick, with or without a velocity gradient of about 30 km at the top of it. Regardless of the model type, positive and similar velocity increases in both P and S velocities at the D″ interface, ranging from 2.7 to 3.8  per cent, are required to fit the data well. Our data rule out velocity decreases in P and S waves at the D″ interface as well as no velocity reduction above the CMB. There are also regions where we do not observe PdP and SdS waves. Collectively, these observations suggest lateral variations in both chemistry and temperature, combined with phase transitions. For instance, ancient oceanic basalt debris from the Farallon slab could be modulating the detection of the D″ reflector in this region.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1093/gji/ggy476DOIArticle
ORCID:
AuthorORCID
Durand, S.0000-0002-2415-6793
Jackson, J. M.0000-0002-8256-6336
Additional Information:© 2018 The Author(s). Published by Oxford University Press on behalf of The Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). Accepted 2018 November 9. Received 2018 November 5; in original form 2018 May 2. Published: 16 November 2018. The authors thank M. Thorne, D. Frost, and one anonymous reviewer for their helpful comments as well as the Editor Martin Schimmel. Data were analysed with Obspy (Beyreuther et al. 2010), maps were drawn with GMT (Wessel & Smith 1991) and the tomographic section was obtained with SeisTomoPy (Durand et al. 2018). Data were downloaded with IRIS. S.D. was supported by the DFG project HAADES DU1634/1-1. J.M.J. was supported through the International Office of WWU, Münster, NSF-CSEDI-EAR-1600956, Caltech, and the W.M. Keck Institute for Space Studies.
Group:Seismological Laboratory, Keck Institute for Space Studies
Funders:
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)DU1634/1-1
University of MünsterUNSPECIFIED
NSFEAR-1600956
CaltechUNSPECIFIED
Keck Institute for Space Studies (KISS)UNSPECIFIED
Subject Keywords:Structure of the Earth; Atlantic Ocean; Probability distributions; Body waves
Record Number:CaltechAUTHORS:20181211-125022062
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20181211-125022062
Official Citation:S Durand, C Thomas, J M Jackson; Constraints on D″ beneath the North Atlantic region from P and S traveltimes and amplitudes, Geophysical Journal International, Volume 216, Issue 2, 1 February 2019, Pages 1132–1144, https://doi.org/10.1093/gji/ggy476
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91685
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:11 Dec 2018 22:33
Last Modified:11 Dec 2018 22:33

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