HR: 09:15h
AN: S41C-06    [Abstracts]
TI: Teleseismic imaging of Northern Cascadia upper mantle in the Explorer region
AU: * Audet, P
EM: paudet@eos.ubc.ca
AF: University of British Columbia, Department of Earth and Ocean Sciences, 6339 Stores Road, Vancouver, BC V6T 1Z4, Canada
AU: Bostock, M G
EM: bostock@eos.ubc.ca
AF: University of British Columbia, Department of Earth and Ocean Sciences, 6339 Stores Road, Vancouver, BC V6T 1Z4, Canada
AU: Cassidy, J F
EM: JCassidy@NRCan.gc.ca
AF: Pacific Geoscience Center, Geological Survey of Canada, 9860 West Saanich Road, Sidney, BC V8L 4B2, Canada
AU: Al-Khoubbi, I
EM: ialkhoub@NRCan.gc.ca
AF: Pacific Geoscience Center, Geological Survey of Canada, 9860 West Saanich Road, Sidney, BC V8L 4B2, Canada
AB: The transition from subduction along the northern Cascadia margin to transcurrent motion between the Pacific and North America plates occurs in the vicinity of northern Vancouver Island. While there is clear evidence for active subduction of the Juan de Fuca plate beneath central and southern Vancouver Island, the situation is more complicated beneath the northern part of the island, where the small Explorer plate is not actively subducting, but rather being over-ridden by North America. It is not clear whether megathrust earthquakes in this area will involve only the Juan de Fuca plate (with a northern limit near Nootka Island), or if they will also include the Explorer plate region (to the vicinity of the Brooks Peninsula). Addressing this question has important implications for seismic hazard on Vancouver Island. To investigate the velocity structure of the upper mantle in the Explorer region, a cross-shaped array composed of 24 portable broad-band seismic stations was deployed on northern Vancouver Island as part of the POLARIS-BC experiment (NVI array). One arm of the array trends NW-SE in the direction parallel to strike and straddles the assumed northern end of the subduction zone, and the second arm trends SW-NE in the direction perpendicular to strike, just north of the extension of the Nootka fault beneath Vancouver Island where convergence is observed. Here we present an analysis of teleseismic data recorded between June 2005 and June 2007 from the entire NVI array. We show preliminary images obtained using receiver function analysis and P-wave traveltime tomography.
DE: 7203 Body waves
DE: 7218 Lithosphere (1236)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: 2007 Fall Meeting