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The Canadian Rockies and Alberta Network (CRANE); new constraints on the Rockies and Western Canada sedimentary basin

Yu Jeffrey Gu, Ahmet Okeler, Luyi Shen and Sean Contenti
The Canadian Rockies and Alberta Network (CRANE); new constraints on the Rockies and Western Canada sedimentary basin
Seismological Research Letters (July 2011) 82 (4): 575-588

Abstract

The Canadian Rockies and the neighboring Alberta Basin mark the transition from the old North American continental lithosphere (east) to young accreted "terranes" (west). Geologic, seismic, and magnetic data in this region have suggested complex crustal domains, conductive anomalies, and major seismic velocity gradients in the mantle. However, the nature of the boundaries between the basement domains and their vertical extents remains controversial due to the lack of exposed geology and limited seismic and electromagnetic receivers. Since 2006, the seismic data coverage and depth sensitivity have received a major boost from the establishment of the Canadian Rockies and Alberta Network (nicknamed CRANE), the first semi-permanent broadband seismic array in Alberta. The availability of the array data provides vital constraints on the regional micro-earthquakes and crust/mantle seismic structures. Among the broad range of ongoing efforts, this study highlights promising results from the analyses of P-to-S wave receiver functions, shear wave splitting amplitudes/directions, and ambient seismic noise. Our preliminary receiver-function stacks show that the base of the crust gradually shallows from approximately 60 km beneath the Rockies near the Canadian-U.S. border to 37-40 km beneath central Alberta; the latter range is consistent with earlier findings from active-source experiments. Converted waves from "littered" crust and/or lithosphere have also been detected at a number of stations in the depth range of 80-130 km. Complexities in the lithosphere are further evidenced by our regional shear wave splitting measurements. We infer a strong east-west change of mantle flow pattern, consistent with present-day plate motion. The spatial distribution of the SKS fast orientations highlights the contrasting crust/mantle structures and histories between the Rockies and adjacent domains. Dynamic effects associated with a migrating continental root east of the province may be important. Finally, our preliminary inversions using ambient seismic noise indicate more than 0.8 km/s in peak-to-peak group velocity variations throughout the crust. The upper crust beneath the Alberta Basin is dominated by low Rayleigh-wave group velocities. A lower-than-expected correlation between seismic velocities and tectonic domain boundaries suggests significant tectonic overprinting in the southern Western Canada Sedimentary Basin. Overall, the broadband seismic data from CRANE could play a key role in uncovering the mysteries of the crust and mantle beneath the transition region between cratons and terranes.


ISSN: 0895-0695
EISSN: 1938-2057
Serial Title: Seismological Research Letters
Serial Volume: 82
Serial Issue: 4
Title: The Canadian Rockies and Alberta Network (CRANE); new constraints on the Rockies and Western Canada sedimentary basin
Affiliation: University of Alberta, Department of Physics, Edmonton, AB, Canada
Pages: 575-588
Published: 201107
Text Language: English
Publisher: Seismological Society of America, El Cerrito, CA, United States
References: 84
Accession Number: 2011-069050
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch maps
N49°00'00" - N60°00'00", W120°00'00" - W110°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201138
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