Edna Maria Facincani

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.

MUDANÇAS AMBIENTAIS QUATERNÁRIAS NO MEGALEQUE FLUVIAL DO AQUIDAUANA, BORDA SUDESTE DO PANTANAL MATOGROSSENSE

O Megaleque do Aquidauana e um trato de sistemas deposicionais, em que o rio Paraguai e a drenagem principal, coletora das aguas de diversos leques fluviais, constituindo de uma importante feicao geomorfologica instalada na Borda Sudeste do Pantanal Mato- rossense, com area de aproximadamente 3.783.48 km². No presente trabalho, utilizando dados orbitais e tecnicas de interpretacao visual de imagens a area foi compartimentada em tres lobos deposicionais distintos denominados de antigo, pre- atual e atual. Estas unidades apresentam em sua superficie geoformas atuais e relictas que evidenciam mudancas ambientais que vem ocorrendo na area desde o Pleistoceno ate o presente. As mudancas sao principalmente de cunho paleohidrologico, dentre as quais podem ser destacadas os lobos deposicionais (relicto e atual) e a planicie incisa (abandonado e ativo), feicoes geomorfologicas que demonstram a paisagem do Megaleque Fluvial do Aquidauana se alterando durante o Quaternario.