Seismotectonics of British Columbia

A comprehensive seismotectonic model is developed to explain the seismicity of British Columbia. In order to do this extensive revisions are made to location and magnitude parameters in the Canadian Earthquake Data File. Fault plane solutions are calculated for all earthquakes possible and all mechanisms previously calculated are examined and upgraded where necessary. It is proposed that the subcrustal suite of earthquakes in the Puget Sound and southern Vancouver Island region are a result of strain caused by phase changes in the descending oceanic lithosphere of the subducting Juan de Fuca plate. The crustal earthquakes above the deeper seismicity can be explained with an oblique subduction model. The distribution of seismicity, the amount of seismicity and the focal mechanisms support these interpretations. The large earthquakes of central Vancouver Island are probably a result of the interaction of the Explorer Plate with the overriding America Plate. In the southern Queen Charlotte Islands thrusting components in the fault plane solutions confirm there is an element of convergence across the pacific/America boundary in this region. The distribution of seismicity suggests all relative plate motion is presently occurring along the Queen Charlotte fault. The Quaternary volcanoes of British Columbia show little correlation with the seismicity pattern except for the eastern end of the Anahim volcanic belt.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat