| Popis: |
Rayleigh wave dispersion curves obtained at twenty-three IRIS seismological stations were used to image group velocities throughout souheastern Brazil. The main geological provinces of the area were clearly identified in the tomographic maps. Two group velocity maps show a strong lateral variation across Parana basin, which was associated with both gravity and geoid anomalies found in regional studies in the area (Molina et al., 1989; Molina and Ussami, 1999). These images also suggest the presence of a high velocity zone in the lower crust, along the coastal region, such as proposed by Molina et al. (1989) beneath the northern part of the Parana basin. A circular high velocity anomaly around Brasilia was found in this study. It is surrounded by low group velocity anomalies, which are probably related to sedimentary rocks. This high group velocity anomaly seems to be associated with Goias Massif and it has a more uniform behavior than south Sao Francisco craton. |
