HR: 0800h
AN: T11B-0570    [Abstracts]
TI: Analysis of Local Earthquakes Recorded by the Batholiths Array in Western British Columbia: Pn Velocity and the State of Stress of the Coast Mountains Batholith
AU: * Jasbinsek, J J
EM: johnjj@uwyo.edu
AF: University of Wyoming Dept. of Geology and Geophysics, 1000 University Avenue, Laramie, WY 82071, United States
AB: The Batholiths Array consisted of 46 broadband seismometers operating for 15 months in 2005-2006. Two 23 station lines with a 12-15 km station spacing operated through Bella Coola (southern line) and through Kitimat (northern line). During the recording period, nine earthquakes with magnitudes ranging from 5.0 to 5.4 and similar epicenters occurred on the offshore Queen Charlotte fault between the ends of the lines approximately 210 km west of the array. Analysis of Pn first arrivals shows significant variations in Pn velocity within each line. In the north Pn velocity changes from 8.0 to 8.1 to 7.9 km/s from SW to NE. In the south Pn velocity changes from 8.0 to 8.2 km/s from W to E. Changes in Pn velocity do not appear to correlate with the surface expression of terrane boundaries. Preliminary earthquake locations for land based earthquake events show a pattern of seismicity following the eastern edge of the Coast Shear Zone and crossing the southern line. The seismicity pattern ceases approximately midway between the northern and southern lines. Focal mechanisms from the largest of these earthquakes will be used to constrain a model for the state of stress in the Coast Mountains Batholith.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting