Research carried out by scholars from the Federal University of Acre (Ufac) identified a concentration of earthquakes in Tarauacá, 400 km from the capital Rio Branco, and raised the hypothesis of the existence of a large geological structure, called the Tarauacá fault.
The researchers analyzed records of earthquakes that occurred since the 1950s with data from the United States Geological Survey (USGS). They classified the tremors by location, depth, magnitude and date they occurred. With this information, they produced maps to identify the regions most at risk of earthquakes.
According to the researchers, this fault may be related to the division of Acre's territory into two tectonic units, called Placa do Juruá and Placa do Purus.
However, the failure is still a scientific hypothesis. The researchers emphasize that more in-depth geophysical studies are still needed to confirm the structure and better understand its relationship with the tremors recorded in the state.
"In fact, we called it the Tarauacá fault because it is a regional context, I believe it is established in this way and now we just need to prove it with more robust data so that we can make progress in this sense", explained Waldemir Lima, professor of the geography course at the Federal University of Acre (Ufac).
Master in geography at Ufac, Cleyton Aguiar Crisóstomo adds that the earthquakes felt in Acre are also linked to a larger geological scenario: The state is close to the Andes, where the Nazca plate dips beneath the South American plate.
"When there is a collision between the plates, the energy released there ends up reaching regions of weakness in these plates. Faults are regions of weakness and that is why, when this shock happens, these earthquakes end up occurring in the Tarauacá region", he explained.
Still according to Waldemir Lima, Cruzeiro do Sul and Mâncio Lima are closer to the Andes, which would explain more shocks in the regions. However, the research identified that the city of Tarauacá is the most affected.
According to him, the characteristics of the relief in the Tarauacá region help explain the occurrence of the events. According to the researcher, a stretch between the municipality and the Gregório River has a different geological configuration.
"What corroborates this is the relief. In a short space of land, 60 kilometers from the city to the Gregório River, there is a different relief configuration, which represents an active regional neotectonic with embedded valleys, with different drainage and very undulating relief", he reported.
By placing these tremors on the map, researchers realized that the events are not distributed randomly. The concentration raised a hypothesis: the existence of a large geological structure in the region.
The tremors noticed in the state occur even hundreds of kilometers from the region where the South American and Nazca plates meet. According to Cleyton, the energy generated by the movement of these plates is released in areas of weakness.
"In the case of Acre, the state is, more or less, 600 or 150 kilometers deep from the plate. So, this means that when the energy is released, it is mitigated and when it reaches the surface it no longer has destructive potential", highlighted the professor.
Although the tremors are felt by residents of the region, Acre does not usually record earthquakes with the same destructive potential observed in regions close to the areas where tectonic plates meet.
"The Acre region, like all of Brazil and South America, is on a plate called the South American plate. But, there is a hypothesis that there is a crack in this plate, which passes through Acre, and this explains the occurrence of earthquakes in the state", he added.
At the end of July, the 5.6 magnitude earthquake recorded near the border between Peru and Brazil had repercussions felt in cities in Acre. Residents reported to g1 that they felt tremors in their homes around 8pm local time, 10pm in Brasília.
United States Geological Survey (USGS), the tremor occurred near the city of Pucallpa, on the Peruvian side of the border. The epicenter was about 60 kilometers from the border between Peru and Acre.
On Thursday (20), residents of Acre felt the earthquake after a 6.7 magnitude earthquake hit Peru and left 3 injured. In the state of Acre, the Legislative Assembly building (Aleac) and other bodies were evacuated.
This was the second earthquake noticed in the state of Acre in 10 days. On the 10th, residents of Mâncio Lima, in the interior of Acre, felt a slight earthquake after the 7.4 magnitude earthquake hit Colombia.
