Orthometric, normal and geoid heights in the context of the Brazilian altimetric network

The extensive use of GNSS positioning, combined with the importance of precise geoid heights for transformation between geodetic and orthometric heights, brings up the discussion of the influence of data uncertainties and the use of variable density values on these estimates. In this sense, we analyze the influence of the topographic masses density distribution and the data uncertainty on the computation of orthometric and geoid heights in stations of the High Precision Altimetric Network of Brazil, considering the Helmert and Mader methods. For this, we use 569 stations whose values of geodetic and normal heights, gravity, and geopotential numbers are known. The results indicate that orthometric heights are more sensitive to density values and to greater heights than to the Helmert and Mader methods applied. Also, we verify that the normal and orthometric heights present significant differences for the analyzed stations, considering the high correlation between the heights, which provide small values of uncertainty. However, our analyses show that the use of the Mader method, along with variable density values, provides either more rigorous or more reliable results

The 2009 earthquake, magnitude mb 4.8, in the Pantanal Wetlands, west-central Brazil

The main goal of this paper is to characterize the Coxim earthquake occurred in June 15th, 2009 in the Pantanal Basin and to discuss the relationship between its faulting mechanism with the Transbrasiliano Lineament. The earthquake had maximum intensity MM V causing damage in farm houses and was felt in several cities located around, including Campo Grande and Goiânia. The event had an mb 4.8 magnitude and depth was 6 km, i.e., it occurred in the upper crust, within the basement and 5 km below the Cenozoic sedimentary cover. The mechanism, a thrust fault mechanism with lateral motion, was obtained by P-wave first-motion polarities and confirmed by regional waveform modelling. The two nodal planes have orientations (strike/dip) of 300°/55° and 180°/55° and the orientation of the P-axis is approximately NE-SW. The results are similar to the Pantanal earthquake of 1964 with mb 5.4 and NE-SW compressional axis. Both events show that Pantanal Basin is a seismically active area, under compressional stress. The focal mechanism of the 1964 and 2009 events have no nodal plane that could be directly associated with the main SW-NE trending Transbrasiliano system indicating that a direct link of the Transbrasiliano with the seismicity in the Pantanal Basin is improbable

Metodologias de interpolação espacial aplicada a dados de espessura crustal na Bacia do Paraná

The use of methods of spatial interpolation of data is becoming increasingly common in geophysical analysis, because of that, currently, several software already contain a lot of these methods, allowing more detailed studies. In the present work to evaluate three methods of interpolation data for crustal thickness of the Paraná Basin, with the intention of making a map of the Moho for the region. The methods are IDW, Spline and Kriging. We compiled 39 data that were a database and analyzed using the software ArcGIS 9.3. The results showed a thicker crust in the central part with thinning to the edge. Traditional methods, IDW and Spline in its results generate anomalies not compatible with the 2.0 model crust. The analysis results of geostatistical Kriging are more refined and consistent, showing no abnormalities point, besides showing more consistent compared with the model, except the northwest, where there is a mismatch between the models due to data exclusivity of gravity, which are less precise than the data of receiver function and seismic.Pages: 3435-344