HR: 1340h
AN: T13A-0431    [Abstracts]
TI: Three-Dimensional Structure in Southern Ontario via Receiver Function Imaging
AU: * Zhang, J
EM: umzhan60@cc.umanitoba.ca
AF: University of Manitoba, Department of Geological Sciences University of Manitoba, Winnipeg, MB R3T 2N2 Canada
AU: Frederiksen, A W
EM: frederik@cc.umanitoba.ca
AF: University of Manitoba, Department of Geological Sciences University of Manitoba, Winnipeg, MB R3T 2N2 Canada
AB: The Precambrian bedrock in Southern Ontario is part of the Grenville province, a complex orogenic belt of circa 1.1 billion years in age that truncates several older geological provinces. In this study, two approaches (common conversion point [CCP] stacking and scattering tomography) were used to characterize 3-D crustal and upper mantle structure across southern Ontario, in a region of approximately 600 by 500 km, based on teleseismic receiver functions recorded by 29 three-component broadband stations deployed by the POLARIS (Portable Observatories for Lithospheric Analysis and Research Investigating Seismicity) array and CNSN (Canadian National Seismograph Network). Our preliminary results from CCP stacking clearly delineate the crust-mantle boundary and several upper mantle structures as continuous, nearly flat features. We detect the Moho at a depth of around 41-50 km, as well as a sub-crustal negative-polarity arrival at 60-80 km which might be correlated with subduction occurring during orogeny. Higher resolution images of crustal structure were obtained using scattering tomography. The Ottawa-Bonnechere Graben can be identified in the NE corner of the study area; as well, southeast dipping features and major crustal discontinuities, including the Moho, agree in some regions with previous controlled-source studies. The two imaging methods used complemented each other, scattering tomography providing greater crustal resolution, while CCP stacking images greater depth. The CCP and tomographic results disagree in some areas, and do not perfectly match previous studies; interpretation of large-scale 3-D structure in southern Ontario is in progress.
DE: 7205 Continental crust (1219)
DE: 7218 Lithosphere (1236)
DE: 7270 Tomography (6982, 8180)
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 9350 North America
SC: Tectonophysics [T]
MN: Fall Meeting 2005