Crustal Structure, Deformation from GPS, and Seismicity Related to Oblique Convergence Along the Queen Charlotte Margin, British Columbia

Download or read book Crustal Structure, Deformation from GPS, and Seismicity Related to Oblique Convergence Along the Queen Charlotte Margin, British Columbia written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Tectonic processes and seismic hazard along the west coast of British Columbia result from oblique convergence between the continental North America plate and the oceanic Pacific and Juan de Fuca plates. This dissertation integrates seismic and geodetic techniques to examine the tectonic interaction along these plate boundaries. The Queen Charlotte Fault zone is the transpressive boundary between the North America and Pacific plates along the northwestern margin of British Columbia. Two models have been suggested for the accommodation of the -20 mm/yr of convergence along the fault boundary: (1) underthrusting; (2) internal crustal deformation. Strong evidence supporting an underthrusting model is provided in this dissertation by a teleseismic receiver function analysis that defines the underthrusting slab. Forward and inverse modelling techniques were applied to receiver function data calculated at two permanent and six temporary seismic stations within the Islands. The modelling reveals a --10 km thick low-velocity zone dipping eastward at 28 interpreted to be underthrusting oceanic crust. The oceanic crust. which may be anisotropic, is located beneath a thin (28 km) westward shallowing (10) continental margin. The majority of seismicity along the Queen Charlotte Fault zone plots within the modelled underthrusting crust, suggesting that these earthquakes are occurring on faults that extend down into the slab or they might be intraslab events. None of the earthquakes within the Queen Charlotte Basin have occurred deep enough to be intraslab earthquakes. The Wadati-Benioff seismicity may be inhibited beneath the basin by the hot young oceanic crust or by the short distance of underthrusting. GPS measurements have been recorded within the Queen Charlotte Islands during 8 years of campaign surveys. The crustal velocity field derived from the GPS data indicates northward margin-oblique motion of 10-15 mm/yr. Comparisons of the observed velocities with elastic dislocati.