Figure 1. Cartoon of the tectonic setting within which the study area lies. The Juan de Fuca Plate is converging toward the North American Plate at a rate of about 40-45 mm per year. This convergence results in subduction of the oceanic Juan de Fuca Plate and crustal stress and strain being exhibited in the continental North American Plate (Figs. 2 and 3).
Figure 2. Change in Baseline Length, Albert Head (western edge of the study area, near Victoria) to Penticton (inland BC). The trend line shows shortening of 5.9 mm/year. For more information on the Western Canada deformation array, see http://www.pgc.nrcan.gc.ca/geodyn/wcda.htm
Figure 3. P-nodal solutions of crustal earthquakes of the Pacific Northwest and southwestern British Columbia show a consistent pattern of margin-parallel, north-south compression, perpendicular to the direction of subduction and perpendicular to the observed strain measured in the GPS array as shown in Figure 2 (see Wang, 2000).