The 1982 COCRUST seismic experiment across the Ottawa-Bonnechere graben and Grenville Front in Ontario and Quebec

Abstract

Summary. During the summer of 1982 the Canadian Consortium for Crustal Reconnaissance using Seismic Techniques (COCRUST) conducted a major long-range seismic refraction and wide-angle reflection experiment across the Grenville province of the Canadian Shield. Three seismic lines each approximately 300 km in length were located (i) along the Ottawa-Bonnechere graben, (ii) perpendicular to the graben and (iii) perpendicular to the Crenville Front. Geological evidence indicates that the graben may have originated from a failed arm of the St Lawrence rift system, and the Grenville Front marks the boundary between the Grenville province and the much older Superior province. Other geological features of the Grenville province that were traversed by the profiles were the Central Metasedimentary belt, and the Central Gneiss belt. Analysis of the data involved conventional traveltime procedures coupled with the use of synthetic seismogram analysis using programs that were written to handle laterally heterogeneous structures. Results from the survey indicate a variation in near surface seismic velocity