An Image Processing Technique to Derive Geological Discontinuities in South America

The aim of this paper is to construc an image from Moho discontinuity in South America. This result can be obtained through global modeling of Rayleigh waves phase and group velocity (ROSA (1986) and SANTA ROSA (1996)). The initial 2-D inversion model was defined according to the geographic position of each block, sized 10 x 10 degrees by ROSA (1986), in the continent and in the ocean. As a result of the inversion, we obtained global group velocity, i.e. the images for the following periods: 50, 55, 60, 65, 70 e 75 seconds (see Figure 1). In the next step, 48 blocks were selected; that is, the number of blocks that cover the whole extension of South America (see Figure 2a). Global phase and group velocity inversions were made for each block, thus determining shear wave versus depth images. Finally, to determine the image of the Mohorocivic discontinuity for South America, we fixed the minimum value for shear wave velocity in 4.6 km/s and interpolated it for all blocks. The final result is the first image of the Moho discontinuity in South America (see Figure 2b). This work was supported by the Brazilian National Council for Scientific and Technological Development (CNPq).