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The structure of the crust and upper mantle under the highest ranges of the Canadian Rockies from a seismic refraction survey

1977; NRC Research Press; Volume: 14; Issue: 2 Linguagem: Inglês

10.1139/e77-022

1480-3313

R. F. Mereu, Sanhita Majumdar, R. E. White,

Seismic Imaging and Inversion Techniques

In the Project Edzoe seismic experiment, the seismic waves from a series of shots fired in Greenbush Lake near Revelstoke B.C. were recorded by the University of Western Ontario at approximately 100 stations along two seismic lines. The first began in the Rocky Mountain Trench, crossed the mountains near Jasper, Alberta and then extended NE across the Plains to Fort McMurray, Alberta, the maximum distance from the shotpoint being 800 km. The second line was roughly in line with the shotpoint and extended from Stanley Falls to Whitecourt, Alberta.An interpretation of the results revealed that the topography of the Moho under the highest ranges of the Rocky Mountains is relatively flat when compared with results from similar experiments on the Canadian Shield. In addition to the typical P n layer, a very high velocity upper mantle layer (8.5 to 8.8 km/s) also exists at a depth of 60 km or approximately 10 km below the Moho. An interesting feature observed on the record sections was the echelon pattern formed by the crustal P wave trains. From a study of theoretical amplitudes it was found that this pattern could be explained by the presence of large positive gradients within the lower crust coupled with a relatively low value of Q near the Moho.