Contemporary crustal movements in Canada

Abstract

Our present knowledge of the patterns and causes of contemporary aseismic movements of the crust in Canada is reviewed. Modern and paleo water-level data and geodetic relevelling data are being used to delineate the regional pattern of vertical movements, but equivalent data on regional horizontal movements are not yet available. The first steps are being taken to relate the emerging regional pattern of vertical movement in Canada to the interactions on the western margin of the America plate and to the spatial variations in seismicity, gravity field, and crustal stress in the plate interior. Viscoelastic modelling of the earth's response to surface loads, and laboratory-based results on possible non-linear rheologies in the mantle have provided a useful theoretical framework for comparing new data on ice-sheet histories with paleo water-level results. Local-scale crustal deformations are being monitored by triangulation, levelling, and gravity networks, as well as by tiltmeters, strainmeters and well-water-level meters. The interpretation of the local deformation data has been facilitated by modelling of the response of inhomogencous-elastic and porous-elastic media. The level of research activity on local aseismic movements in different areas of Canada corresponds to the seismotectonic significance of the areas.