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Ambient seismic noise tomography of Canada and adjacent regions: Part I. Crustal structures

Kao, Honn and Behr, Yannik and Currie, Claire A. and Hyndman, Roy and Townend, John and Lin, Fan-Chi and Ritzwoller, Michael H. and Shan, Shao-Ju and He, Jiangheng (2013) Ambient seismic noise tomography of Canada and adjacent regions: Part I. Crustal structures. Journal of Geophysical Research. Solid Earth, 118 (11). pp. 5865-5887. ISSN 2169-9313. http://resolver.caltech.edu/CaltechAUTHORS:20140114-080813432

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Abstract

This paper presents the first continental-scale study of the crust and upper mantle shear velocity (V_s) structure of Canada and adjacent regions using ambient noise tomography. Continuous waveform data recorded between 2003 and 2009 with 788 broadband seismograph stations in Canada and adjacent regions were used in the analysis. The higher primary frequency band of the ambient noise provides better resolution of crustal structures than previous tomographic models based on earthquake waveforms. Prominent low velocity anomalies are observed at shallow depths (<20 km) beneath the Gulf of St. Lawrence in east Canada, the sedimentary basins of west Canada, and the Cordillera. In contrast, the Canadian Shield exhibits high crustal velocities. We characterize the crust-mantle transition in terms of not only its depth and velocity but also its sharpness, defined by its thickness and the amount of velocity increase. Considerable variations in the physical properties of the crust-mantle transition are observed across Canada. Positive correlations between the crustal thickness, Moho velocity, and the thickness of the transition are evident throughout most of the craton except near Hudson Bay where the uppermost mantle V_s is relatively low. Prominent vertical V_s gradients are observed in the midcrust beneath the Cordillera and beneath most of the Canadian Shield. The midcrust velocity contrast beneath the Cordillera may correspond to a detachment zone associated with high temperatures immediately beneath, whereas the large midcrust velocity gradient beneath the Canadian Shield probably represents an ancient rheological boundary between the upper and lower crust.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1002/2013JB010535 DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/2013JB010535/abstractPublisherArticle
Additional Information:© 2013 American Geophysical Union. Received 17 July 2013; revised 25 October 2013; accepted 29 October 2013; published 21 November 2013. We are grateful to an anonymous Associate Editor, an anonymous reviewer, and Lapo Boschi for their constructive comments. Fiona Darbyshire kindly provided the dispersion measurements of earthquake surface waves. Digital waveform data were obtained from the data centers of the Canadian Hazard Information Service and Incorporated Research Institutions for Seismology. We benefited from discussion with David Schneider, Sonya Dehler, and Yu-Lien Yeh. YB and JT acknowledge the support of the Marsden Fund of the Royal Society of New Zealand. MHR acknowledges support from US NSF grant EAR-1252085. This research was partially supported by a NSERC grants to HK (RGPIN 418268–2013) and to Currie and Hyndman. ESS contribution number 20130238.
Funders:
Funding AgencyGrant Number
Royal Society of New Zealand Marsden FundUNSPECIFIED
NSFEAR-1252085
NSERCRGPIN 418268–2013
Subject Keywords:ambient seismic noise; Canada; crustal structure; shear velocity structure; crust-mantle transition; midcrust discontinuity
Other Numbering System:
Other Numbering System NameOther Numbering System ID
ESS Contribution20130238
Record Number:CaltechAUTHORS:20140114-080813432
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140114-080813432
Official Citation:Kao, H., Y. Behr, C. A. Currie, R. Hyndman, J. Townend, F.-C. Lin, M. H. Ritzwoller, S.-J. Shan, and J. He (2013), Ambient seismic noise tomography of Canada and adjacent regions: Part I. Crustal structures, J. Geophys. Res. Solid Earth, 118, 5865–5887, doi:10.1002/2013JB010535
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43351
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:30 Jan 2014 18:07
Last Modified:25 Sep 2014 21:48

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