| We present the results of a study of the dispersion characteristics of broadband fundamental mode seismic surface waves propagating across South America, Antarctica and the surrounding oceans. We analyzed data from 765 earthquakes recorded at 48 seismic stations for South America and from 576 earthquakes recorded at 44 stations for Antarctica, which produced 11,700 dispersion curves for Rayleigh Waves and 8,200 dispersion curves for Love waves. The main results of this study are represented in the form of group velocity maps for Rayleigh (20 s--175 s) and Love (20 s--125 s) waves. The South American maps reveal a number of sedimentary basins across the continent (such as Maturin-Llanos, Maranon-Ucayali-Madre de Dios, Chaco-Tarija, Parana Basins), the Caribbean, and western Gulf of Mexico; the thickened crust beneath the Andes, the Altiplano, and the Brazilian Highlands; sub-continental roots and the Galapagos Ridge and the Galapagos hot spot. The Antarctic maps demonstrate such features as the thick crust in East Antarctica and beneath the Transantarctic Mountains, mid-ocean ridges, the East Antarctic craton, and a number of hot spots. The average lateral resolution is on the order of 500--550 km on the Antarctic continent and 650--750 km on the South American continent, which is a significant improvement over that reported in global scale studies. The difference between these two results is likely due to different algorithms used to assess the resolution on the both continents. We produced azimuthal anisotropy maps for the 2psi component of group velocity across Antarctica and the surrounding oceans; these maps correlate fairly well with those of the global study (Trampert and Woodhouse, 1996). The estimated group velocity maps can be inverted to produce new shear velocity models across the studied regions, which may improve knowledge of the crust and the uppermost mantle beneath South America and Antarctica. |
