Seismic Surveys in the Northeastern Portion of the Paraná Basin

Preliminary results of seismic refraction and reflection surveys carried out in Nuporanga, located in the NE portion of the Parana Basin, are presented. The objective of these surveys is to determine the local underground geological structure in order to be used to determine hypocenters of focal seismic activity and to assist the ground water exploitation in Nuporanga. Other geophysical methods (gravimetry, geothermics, magnetotelluric and well logging) are being used as complementary tools for this study. Results from the seismic surveys defined a preliminary model beneath Nuporanga with a thin discontinuous layer of soil of no more than 10m thick with Vp=O.32km/s overlying an also discontinuous layer of Bauru Group sediments with no more than 30m of depth and Vp=1.8km/s,underlying it there is a Vp=2.8km1sbed that is a probable weathered layer of volcanic rock of not yet determined thickness, followed by the Geral basalt with Vp=5.1km/s up to depth of around 400m. The Paleozoic sediments were modelled with 1200m of thickness and Vp=4.0km/s to justify the crystalline basement at 1600m of depth with Vp=6.0km/s