Seismic anisotropy associated with continental lithosphere accretion beneath the CANOE array, Northwestern Canada

Anna M. Courtier, James B. Gaherty, Justin Revenaugh, Michael G. Bostock, Edward Garnero

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

We examine upper-mantle seismic anisotropy beneath the cordillera and craton of northwestern Canada using the multi-event station averages of shear-wave splitting of SKS, SKKS, and sSKS phases recorded during the Canadian Northwest Experiment (CANOE). Splitting times derived from multi-event averaging at each station range from 0 to 1.4 s, with an array average of ~0.65 s. Over broad portions of the array, fast directions are coherent and roughly consistent with the direction of absolute plate motion in a hotspot reference frame, suggesting that coherent asthenospheric fabric underlies the plate in much of the region. Within this broad framework, fast directions and splitting times show marked variability over length scales of 50-200 km, and are generally correlated with surface and/or crustal tectonics. Anomalous splitting is observed across an ancient suture within the cratonic lithosphere, apparently associated with complex dipping fabric produced during continental assembly. The deformation front of the Canadian Rockies correlates with a significant change in splitting behavior, consistent with the front range demarking the craton-cordillera transition within the mantle. Splitting times are small across much of the cordillera, indicating that lithospheric and/or asthenospheric fabric is weaker or less coherent than beneath the craton. In the western cordillera, fast directions rotate abruptly to parallel the plate boundary, implying that fabric associated with plateboundary deformation extends ~200 km into the North American continent.

Original languageEnglish (US)
Pages (from-to)887-890
Number of pages4
JournalGeology
Volume38
Issue number10
DOIs
StatePublished - Oct 2010

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seismic anisotropy
continental lithosphere
cordillera
accretion
craton
experiment
wave splitting
plate motion
plate boundary
S-wave
upper mantle
hot spot
lithosphere
mantle
tectonics
fabric
station

ASJC Scopus subject areas

  • Geology

Cite this

Seismic anisotropy associated with continental lithosphere accretion beneath the CANOE array, Northwestern Canada. / Courtier, Anna M.; Gaherty, James B.; Revenaugh, Justin; Bostock, Michael G.; Garnero, Edward.

In: Geology, Vol. 38, No. 10, 10.2010, p. 887-890.

Research output: Contribution to journalArticle

Courtier, Anna M. ; Gaherty, James B. ; Revenaugh, Justin ; Bostock, Michael G. ; Garnero, Edward. / Seismic anisotropy associated with continental lithosphere accretion beneath the CANOE array, Northwestern Canada. In: Geology. 2010 ; Vol. 38, No. 10. pp. 887-890.
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