A Crustal Structure Study of South America

Variations in the average crustal thickness of the South American platform were determined by measuring fundamental mode Rayleigh wave dispersion between nine pairs of South American WWSSN seismograph stations and inverting the measurements to obtain average shear wave velocity-depth models across the platform. Additional models were derived from the Rayleigh wave dispersion data previously measured over eastern South America. Both sets of models were interpreted in terms of average crustal thickness and average crustal shear wave velocity. The results obtained were depicted in a contour map of crustal thickness. Average values for seismic velocities in the crust and upper mantle were calculated and compared with maps of regional gravity models, MAGSAT magnetic anomalies, and major tectonic features. The correlations and relationships discovered are discussed.