Artículos de revistas
Shear wave velocities beneath the eastern part of Brazil
Shear wave velocities beneath the eastern part of Brazil
Autor
de Souza, Jorge Luis; Observatorio Nacional, Departamento de Geofísica, Rio de Janeiro, Brasil.
Institución
Resumen
Rayleigh wave dispersion curves from seventeen earthquakes which occurred in the North Atlantic Ocean area are used to obtain the shear wave velocity structure of the eastern part of the Brazilian territory. The dispersion curves were divided into three groups of paths (A, B, and C) according to geographical position of the epicenters, and a dispersion curve representative of each path was computed. The invesion results of these dispersion curves show that the crustal structure is composed basically of three layers with S-wave velocities varying from 3.30-3.57 km/s, 3.52-3.66 km/s and 3.86-3.92 km/s, respectively. The sub-Moho layer is characterized by shear wave velocities varying from 4.41 to 4.43 km/s. Path C exhibits a sub-Moho thickness thinner than the other two paths. Below the sub-Moho layer, shear wave velocities of 4.27 km/s and 4.22 km/s are found in both paths A and C, but it ha been clearly resolved only in path C where the S-wave velocity was assumed to be 4.22 km/s. A comparative analysis between the models of eastern Brazil and those of eastern South America (Hwang and Mitchel, 1987) and Antartica (Dewart and Toksoz, 1965; Singh, 1994). This is probably related to the past existence of Gondwanaland. El perfil de velocidades de ondas S bajo Brasil Oriental fue obtenido de datos de dispersión de ondas Rayleigh para 17 sismos con epicentro en el Atlántico Norte. La inversión sugiere una estructura de tres capas con velocidades S de 3.30-3.57 km/s, 3.52-3.66 km/s y 3.86-3.92 km/s. Bajo el Moho se encuentran velocidades de 4.41-4.43 km/s. Algunas variaciones se discuten para cada una de las trayectorias. El modelo sugerido es similar a modelos anteriores para Sudamérica y Antártica.