Abstract

During June and July of 1968 the Geological Survey of Canada participated in the Dominion Observatories crustal seismic experiment centered on the Grenville front in north central Quebec. Participation was to the extent of recording the shots of the experiment at locations subadjacent to the Appalachian front from Rimouski and Rivière Du Loup, Québec to Edmundston, New Brunswick. Recordings from a three component station were taken on photographic paper, and also on frequency modulated magnetic tape. A preliminary study of 19 Pn first arrivals results in velocities for the upper mantle ranging from 8.08 km/s to 8.23 km/s with a mean of 8.15 km/s under the shots. Under the stations Pn events show velocities for the upper mantle ranging from 7.81 km/s to 8.65 km/s with a mean of 8.15 km/s. A least-squares time-term analysis for Pn events results in a velocity of 7.94 ± 0.42 km/s at the 90% confidence level. This solution shows large residual times ranging between ±0.7 s which probably imply complex geological structures near the shots and the recording stations. Time and distance data are summarized as well as details of computations.

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