LITH5.0: A revised crustal model for Canada based on Lithoprobe results

During the last 15 yr, numerous seismic refraction experiments have been conducted over the Canadian landmass, most as part of the Lithoprobe initiative. The new results provide the basis for revising existing global models of crustal structure, e.g. CRUST5.1 (Mooney et al. 1998), which do not incorporate the new Lithoprobe data. The crustal model discussed here, LITH5.0, combines the Lithoprobe and CRUST5.1 data to provide better constraints on crustal structure in Canada. The objectives of the study are to: (1) compile available new data into a single, consistent database of crustal thickness and velocity, including the uppermost mantle (Pn) velocity; and (2) to construct a revised 5° x 5° crustal model of the Canadian landmass, in a format that is generally compatible with existing global models. The Lithoprobe results suggest a 5.5 km average root mean square (rms) crustal thickness difference between LITH5.0 and CRUST5.1. Even with the incorporation of the new data, the geographic coverage in north and central Canada remains sparse. The new model does not explicitly incorporate geological constraints, but instead relies on spherical spline interpolation for extrapolating values into regions that lack control. To illustrate the implications of this new crustal model, we use LITH5.0 to correct for the isostatically compensated crustal heterogeneity in order to obtain improved estimates of the dynamic surface topography. The latter provides important constraints on the density structure of the uppermost mantle.