HR: 1340h
AN: V43B-1368    [Abstracts]
TI: Lithospheric Structure Across the Cordillera-Craton Transition in NW Canada from Surface Waves Traversing the CANOE Array
AU: * Gaherty, J B
EM: gaherty@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia U. 61 Rt 9W, Palisades, NY 10964, United States
AU: Chen, P
EM: pochen@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia U. 61 Rt 9W, Palisades, NY 10964, United States
AU: Zhao, L
EM: zhaol@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, Taipei, 115, Taiwan
AU: Bostock, M
EM: bostock@eos.ubc.edu
AF: Earth and Ocean Sciences, UBC, Vancouver, BC V6T 1Z4, Canada
AU: Revenaugh, J
EM: justinr@unm.edu
AF: Geology and Geophysics, U. Minnesota, Minneapolis, MN 55455, United States
AU: Garnero, E
EM: garnero@asu.edu
AF: Earth and Space Exploration, ASU, Tempe, AZ 85287, United States
AB: The Canadian Northwest Experiment (CANOE) is a nearly sixty-station broadband PASSCAL array extending from the Slave Craton in the Canadian NWT, across the Canadian Rockies in northern British Columbia and Yukon and south to Edmonton, Alberta. The array crosses a series of compressive orogens that span 4 Ga of geologic time and are undisrupted by later periods of extension or extensive volcanism, and thus provide an ideal platform for studying the growth of continental cratons through accretion. There are two competing hypothesis for the nature of the cordillera-craton transition in this region: (1) Terranes accreted in the cordillera during the Mesozoic are lithospheric-scale features. This suggests substantial growth of the North American continent since the Proterozoic, and a craton boundary near the deformation front. (2) Terranes are thin-skin thrust features overlying Proterozoic North American lithosphere. This suggests little continental growth since the Proterozoic, and a craton boundary near the Pacific coast. Surface waves traversing the CANOE array provide an excellent data set to evaluate these hypotheses. We have developed and applied a new multi-station cross-correlation procedure to precisely measure the frequency-dependent travel times and amplitudes of Love and Rayleigh waveforms traversing the array. The data are derived from recordings of regional and teleseismic earthquakes recorded between June 2004 and Sept 2005. Using accurate three-dimensional sensitivity kernels for both amplitude and phase, these data are inverted for 3D tomographic images of anisotropic shear- velocities in the crust and upper- mantle across the transition from craton to cordillera. Preliminary results suggest a sharp lateral gradient in both shear velocity and shear anisotropy in the lithospheric mantle that is located very close to the current deformation front, consistent with hypothesis (1). The surface-wave observations will be integrated with receiver function, shear-wave splitting, and body-wave tomography data, proving a comprehensive portrait of lithospheric structure across the transition.
DE: 7270 Tomography (6982, 8180)
DE: 8103 Continental cratons
DE: 8180 Tomography (6982, 7270)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting