Abstract
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.
Highlights
IntroductionThe Pantanal Basin has been regarded as one of the seismic regions of Brazil (Branner 1912, Berrocal et al 1984) as shown in Fig. 1. According Sykes (1978) and Talwani and Rajendran (1991), intraplate earthquakes are the result of ruptures along pre-existing zones of weakness, located near structural inhomogeneities, which may concentrate local stress and, added to regional stress, are −75° 5° −70° −65° −60° −55° GS −50° −45° −40° −35°
The objectives of this paper are to characterize the earthquake occurred in the Pantanal Nhecolândia, Taquari Fan on June 15th, 2009 at 22:14:45 UTC highlighting its location, magnitude, intensity and the possible relationship between the faulting mechanism of the event with the Transbrasiliano Lineament (TBL)
The two largest earthquakes recorded in the Pantanal sedimentary basin were a) Miranda, February 13th, 1964, magnitude mb 5.4 (Assumpção and Suárez 1988), and b) Coxim, of June 15th, 2009, with magnitude mb 4.8
Summary
The Pantanal Basin has been regarded as one of the seismic regions of Brazil (Branner 1912, Berrocal et al 1984) as shown in Fig. 1. According Sykes (1978) and Talwani and Rajendran (1991), intraplate earthquakes are the result of ruptures along pre-existing zones of weakness, located near structural inhomogeneities, which may concentrate local stress and, added to regional stress, are −75° 5° −70° −65° −60° −55° GS −50° −45° −40° −35°
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