Crustal velocity structure in the eastern Insular and southernmost Coast belts, Canadian Cordillera
Seismic refraction data recorded along a 330 km cross-strike profile through the eastern Insular and southernmost Coast belts of the Canadian Cordillera are interpreted using an iterative combination of traveltime inversion and amplitude forward modelling. The resultant model is characterized by large lateral variations in velocity. The most significant of these variations is a decrease in upper and middle crustal velocities to the east of the surface trace of the Harrison fault, which likely represents the transition from crust of the Insular superterrane to that of the Intermontane superterrane. This interpretation is consistent with some present geological models that place the possible (probable) location of the suture between the two superterranes less than 20 km east of the Harrison fault. Velocities at the base of the upper crust average 6.4 and 6.2 km/s west and east of the fault, respectively. Mid-crustal velocities average 6.6–6.9 km/s to the west and 6.35–6.45 km/s to the east of the fault. Low...