A large and deep earthquake was recorded in Brazil on Tuesday night (7). The magnitude 6.5 quake occurred at more than 620 km depth, according to data from the USGS (the US Government Geological Service).
It had its epicenter in Acre, 108 km southwest of the city of Tarauacá, at a point close to the border with Peru. So far, there are no reports of casualties or destruction caused by the earthquake.
“In Acre, the tremor is so deep that, although the magnitude is very high, it will not cause problems on the surface. Destruction is practically impossible”, says Bruno Collaço, a seismologist at USP (University of São Paulo).
Brazil, since 1950, has already registered at least 10 earthquakes with a magnitude greater than that of this Tuesday, according to information from the USGS itself, a reference on the subject. The largest of them, of magnitude 7.6, took place in 1963, with its epicenter also in Acre.
The USP researcher even explains that Tuesday’s tremor should be classified as an Andean earthquake —referring to the Andes Mountains—, and not a “Brazilian” earthquake, despite the fact that the epicenter was recorded in Acre.
That’s because the earthquake was caused by the contact between the Nazca tectonic plate (which is on the west coast of South America) and the South American plate. According to Collaço, there was the so-called subduction, a term used when one plate goes under another.
The so-called Brazilian tremors occur when the African plate “pushes” the South American plate. An example is the earthquake with magnitude 6.2 registered in Serra do Tombador, Mato Grosso, in 1955, considered until today as the biggest “Brazilian tremor”.
While Andean earthquakes occur hundreds of kilometers deep, Brazilian tremors occur closer to the surface, up to 15 kilometers. Therefore, its effects can be much greater and more felt by the population, even with a smaller magnitude.
According to Collaço, there are magnitude 3 Brazilian earthquakes practically every week. Those of magnitude 4 occur two to three times a year and those of magnitude 5, every five years. Those that reach magnitude 6, such as Serra do Tombador, occur approximately every 50 years.
The researcher also says that the tool “Did you feel there?”, from the USP Seismology Center, helps to record earthquakes in Brazil. With it, anyone can report if they try to feel an earthquake in the country.
Reporting these events ends up helping to form the earthquake catalog of Brazilian researchers.
