Crustal structure of the southeastern Brazilian continental margin from surface wave dispersion

Abstract

Source-station Rayleigh wave group velocities are decomposed to obtain pure continental shelf dispersion curves along three profiles. Inversion results of these dispersion curves indicate that the upper crust is dominated by sediments and high velocity sedimentary rocks with shear wave velocities varying from 1.32 to 2.90 km/s. The intermediate crustal layer has assumed shear wave velocities typical of crystalline basement (3.06 :5:~:5:3.38 km/s). The lower crust seems to be composed of a transitional layer (4.02:5:~:5:4.22 km/s), similar to those observed at other passive continental margins (e.g., Dainty et al., 1966; Calcagnile et al., 1982). These results are in agreement with those of a recent surface wave study conducted in the same area (Souza, 1995). Moho boundary is clearly defined around 36±4 km depth, but a reduction in the crustal thickri.ess is observed from profile A to C.