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TitleAmbient seismic noise tomography of Canada and adjacent regions: Part I. Crustal structures
AuthorKao, H; Behr, Y; Currie, C A; Hyndman, R; Townend, J; Lin, F -C; Ritzwoller, M H; Shan, S -J; He, J
SourceJournal of Geophysical Research vol. 118, no. 11, 2013 p. 5865-5887, https://doi.org/10.1002/2013JB010535
Year2013
Alt SeriesEarth Sciences Sector, Contribution Series 20130238
PublisherAmerican Geophysical Union
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia; Alberta; Saskatchewan; Manitoba; Ontario; Quebec; New Brunswick; Nova Scotia; Prince Edward Island; Newfoundland and Labrador; Northwest Territories; Yukon; Nunavut
NTS1; 2; 3; 10; 11; 12; 13; 14; 15; 16; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 52; 53; 54; 55; 56; 57; 58; 59; 62; 63; 64; 65; 66; 67; 68; 69; 72; 73; 74; 75; 76; 77; 78; 79; 82; 83; 84; 85; 86; 87; 88; 89; 92; 93; 94; 95; 96; 97; 98; 99; 102; 103; 104; 105; 106; 107; 114O; 114P; 115; 116; 117; 120; 340; 560
Lat/Long WENS-141.0000 -50.0000 90.0000 41.7500
Subjectsgeophysics; tectonics; seismic interpretations; seismic surveys; seismic data; crustal structure; tomography; tomographic inversion
Illustrationslocation maps; histograms; plots
ProgramTargeted Hazard Assessments in Western Canada, Public Safety Geoscience
AbstractThis paper presents the first continental-scale study of the crust and upper mantle shear velocity (Vs) 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 Vs is relatively low. Prominent vertical Vs 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.
Summary(Plain Language Summary, not published)
This paper presents the first continental-scale study of the crust and upper mantle shear-velocity (Vs) structure of Canada and adjacent regions. Continuous seismic waveform data recorded between 2003 and 2009 with 788 seismograph stations in Canada and adjacent regions are used in the analysis. The utilization of continuous waveform analysis provides better resolution of crustal structures than previous tomographic models based on earthquake arrival times. 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 velocities. Considerable variations in the physical properties of the crust¿mantle transition are observed across Canada. The mid-crust velocity contrast beneath the Cordillera may be related to the high temperatures immediately beneath, whereas the large mid-crust velocity gradient beneath the Canadian Shield probably represents a rheological boundary between the upper and lower crust.
GEOSCAN ID293067