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Abstract

Seismic explosion data obtained by the Dominion Observatory in the Vancouver Island region from 1953 to 1963 have been restudied by both the travel-time and the time-term methods. From the first method, a new four layer model crust was constructed: In addition to the sedimentary, a granitic, and basaltic layers, suggested by White (1962), an ultrabasic layer of more than 22 km in thickness and Vp = 7.1 km/sec was recognized. From the time-term method, this layer structure was supported and the possibility of a major structural feature running across the island is suggested by the faults on each side and the gravity anomaly extending between them. The Mohorovicic discontinuity was not observed. A possibility interpretation of the abnormal character is given, and the complementary gravity and geomagnetic depth sounding evidence presented.