The intraplate Porto dos Gaúchos seismic zone in the Amazon craton — Brazil

The 2012–2013 Montes Claros earthquake series in the São Francisco Craton, Brazil: new evidence for non-uniform intraplate stresses in mid-plate South America

“…The largest recorded event in this stable region was the 1955 m b = 6.2 Serra do Tombador earthquake (Barros et al 2009), which is at least one magnitude unit less than the largest recorded magnitude in other stable continental interiors in the world (e.g. India, North America; Johnston 1989).…”

Basement depths in the Parecis Basin (Amazon) with receiver functions from small local earthquakes in the Porto dos Gaúchos seismic zone

“…In March of 1998 and March of 2005, the two largest earthquakes in the seismic area of Porto dos Gaúchos were recorded: 5.2 m b and maximum Modified Mercalli (MM) intensity VI, and 5.0 m b and maximum intensity V (MM), respectively. Their aftershocks were studied with two University of Brasília (UnB) local seismographic networks (Barros et al, 2009, Barros et al, 2011. The first network of 10 stations (not all operating simultaneously) had an approximate diameter of 70 km and recorded over 2500 microearthquakes between March 1998 and December 2002.…”

“…Since then, no other earthquake has been located in the area of the 1955 event. However, in Porto dos Gaúchos, 100 km NE of the 1955 epicenter, a recurrent seismicity has been observed since 1959, two years after the arrival of the first inhabitants in the region (Barros et al, 2009). Two magnitude 5 earthquakes have occurred in Porto dos Gaúchos, one in 1998 and the other in 2005, with aftershock sequences lasting for more than four years each.…”

“…Two magnitude 5 earthquakes have occurred in Porto dos Gaúchos, one in 1998 and the other in 2005, with aftershock sequences lasting for more than four years each. These two aftershock sequences were studied with local seismographic networks (Barros et al, 2011;Barros et al, 2009;Barros, 2010). This active area of the Parecis basin has been called the Porto do Gaú-chos Seismic Zone (PGSZ).…”

Determinação de parâmetros de fonte de eventos locais e regionais por inversão de formas de ondas

“…The σ1 and σ2 axes are nearly horizontal (15° and 6°); the σ3 axis is nearly vertical (74°), corresponding to the reverse faulting regime. Sul Americana e apresenta uma sísmicidade relativamente baixa, inclusive menor do que aquela observada em outras regiões intraplacas similares, como é o caso do leste dos Estados Unidos, da Índia e da Austrália (Barros, et al, 2009 20/11/198020/11/ (Berrocal et al, 1984, João Câmara -RN, sismo de 30/11/1986 (Ferreira et al, 1987) e Codajás -AM, sismo de 05/08/1983 (Assumpção et al, 1983). Os eventos do NE produziram danos a construções de baixa qualidade e gerou um êxodo de moradores da zona rural de Joao Câmara e Pacajus.…”