Explosion refraction studies have been carried out in areas adjacent to Vancouver Island, including the Strait of Georgia and Johnstone Strait and along the west coast of the Island. A refraction line has also been observed from a large explosion in Seymour Narrows, eastward through the mountains and for some distance across the plains of Alberta. Although the surficial strata complicate the interpretation, a series of short refraction profiles consistently reveal the presence of an intermediate layer with velocity of about 6.8 km/sec. in the coastal area. The depth to the upper boundary of this layer varies from about 11 km. along the west coast of the Island to less than 5 km. in the Strait of Georgia and along the east side of the Island. The longer range observations parallel to the coast indicate this layer to be more than 40 km. thick. On the profile eastward through the mountains a velocity of 7.8 km/sec. has been found for Pn, from an unreversed profile, with a crustal thickness of approximately 30 km.

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