Brazil sits in the middle of its plate, far from where the real energy builds up
Na quinta-feira à noite, os moradores de São Paulo sentiram um tremor sutil vindo de 2.200 quilômetros de distância — um terremoto de magnitude 7,4 que sacudiu o deserto do Atacama, no Chile. As ondas sísmicas atravessaram o continente em cerca de cinco minutos, lembrando que a inquietação da Terra não conhece fronteiras políticas. Para o Brasil, situado no interior da placa Sul-Americana, o episódio foi menos um alerta do que uma rara janela para compreender as forças profundas que moldam o planeta.
- Um terremoto de magnitude 7,4 liberou energia equivalente a 32 bombas de Hiroshima nas profundezas do Atacama chileno, enviando ondas sísmicas a 7,5 km por segundo pelo manto terrestre.
- Em São Paulo e outras 14 cidades do estado, moradores — especialmente nos andares mais altos — sentiram o chão oscilar de forma inesperada, gerando confusão e relatos nas redes sociais.
- A geologia urbana amplificou o fenômeno: bacias sedimentares sob regiões como a Avenida Paulista intensificaram a propagação das ondas, explicando por que alguns bairros sentiram o tremor enquanto vizinhos próximos não perceberam nada.
- Especialistas reafirmam que o risco de um grande terremoto atingir o Brasil diretamente é muito remoto, já que o país está no interior da placa tectônica, longe das zonas de colisão responsáveis pelos maiores abalos.
Na noite de quinta-feira, um tremor sutil mas inconfundível percorreu prédios residenciais e comerciais de São Paulo. A origem estava a 2.200 quilômetros de distância: um terremoto de magnitude 7,4 que atingiu a região de San Pedro do Atacama, no Chile, e fez vibrar ao menos quinze cidades do estado paulista.
A energia liberada pelo abalo foi equivalente a cerca de 32 bombas de Hiroshima, segundo o Serviço Geológico do Brasil. Ondas sísmicas primárias percorreram o manto terrestre a 7,5 km por segundo, chegando a São Paulo em aproximadamente cinco minutos. O terremoto ocorreu a 116 quilômetros de profundidade, na zona de subducção onde a placa oceânica de Nazca mergulha sob a placa Sul-Americana a uma taxa de 74 milímetros por ano — o mesmo processo que torna toda a costa oeste da América do Sul sismicamente ativa.
Nem todos os paulistanos sentiram o tremor da mesma forma. Moradores de andares mais altos perceberam a vibração com mais intensidade, pois as estruturas amplificam o movimento sísmico à medida que ele sobe. Além disso, partes da cidade assentam sobre bacias sedimentares que facilitam a propagação das ondas — regiões sob a Avenida Paulista, por exemplo, registraram o fenômeno enquanto bairros vizinhos não notaram nada.
Para o Brasil, o episódio é mais uma curiosidade geológica do que um sinal de perigo. O país está no interior da placa Sul-Americana, longe das bordas onde ocorrem os maiores terremotos. Os abalos mais significativos já registrados em solo brasileiro — como os de Mato Grosso em 1955 e os recentes no Acre — causaram danos mínimos. A Defesa Civil de São Paulo aproveita a ocasião para lembrar as orientações básicas: agachar, proteger a cabeça e o pescoço, e evitar elevadores após qualquer tremor. Não por alarmismo, mas por prudência.
The ground shifted beneath São Paulo on Thursday night, a subtle but unmistakable tremor that rippled through apartment buildings and office towers across the city. The source was 2,200 kilometers away—a 7.4 magnitude earthquake that struck near the small Chilean town of San Pedro do Atacama. The vibration reached at least fifteen cities across São Paulo state, a reminder that the earth's movements do not respect borders.
To understand how seismic waves travel such distances, imagine throwing a stone into still water. The ripples spread outward in concentric circles, weakening as they move away from the point of impact. The Chilean earthquake released something far more powerful than a stone—energy equivalent to roughly 32 Hiroshima bombs, according to Brazil's Geological Service. That energy propagated through the crust, the uppermost layer of Earth's surface extending to depths of about 100 kilometers.
The earthquake originated 116 kilometers below the surface, already within the mantle—the layer beneath the crust. Primary seismic waves travel through the mantle at an average speed of 7.5 kilometers per second, according to George Sand, a physicist and professor at the University of São Paulo's Department of Geophysics. The journey from Chile to São Paulo took roughly five minutes. The waves slow as they pass through the crust, which is neither linear nor uniform, but the speed through the mantle alone is enough to carry the tremor across the continent.
The earthquake occurred at a collision zone between two tectonic plates: the South American plate, which carries Brazil and its neighbors, and the Nazca plate, which lies beneath the Pacific Ocean. This is a process called subduction. The Nazca plate, being oceanic and denser, slides beneath the continental South American plate. Energy accumulates at this boundary until it releases suddenly, sending waves in all directions. This same process occurs along the entire western coast of South America, from southern Argentina through Colombia. The Nazca plate descends beneath the South American plate at a rate of 74 millimeters per year.
Because Brazil sits in the interior of the South American plate rather than at its edge, major earthquakes are extremely unlikely. The largest tremors, those exceeding magnitude 7, occur at plate boundaries. Brazil's most significant recorded earthquakes happened in remote regions far from population centers. In 1955, a magnitude 6.2 earthquake struck 370 kilometers north of Cuiabá in Mato Grosso. In 1980, a magnitude 5.2 tremor was felt across much of the Northeast, damaging homes in Pacajus, Ceará. More recently, Acre state experienced earthquakes in January of this year and in 2022, with magnitudes of 6.6 and 6.5 respectively, and in 2019, a magnitude 6.8 earthquake struck near Rio Branco. These events caused minimal damage. The possibility of a major earthquake like the Chilean one striking Brazil directly remains, as one expert put it, very remote.
Why did some people in São Paulo feel the tremor while others did not? The answer lies in building height and geology. Residents in taller buildings, particularly those on upper floors, felt the vibration more intensely. When the ground beneath a structure begins to vibrate, the building amplifies that motion upward, making the effect more noticeable at higher elevations. Additionally, portions of São Paulo and surrounding regions sit atop sedimentary basins—layers of accumulated rock and sediment deposited over millions of years. These basins facilitate the propagation of seismic waves. Even a weak wave arriving from a distance can be amplified as it passes through these geological formations. Areas beneath Avenida Paulista, for instance, sit on such a basin, which is why some neighborhoods registered the tremor while others nearby felt nothing.
Though the risk remains minimal, São Paulo's Civil Defense offers practical guidance. If a tremor occurs, the recommended response is to crouch, protect the head and neck with the arms, and hold steady until the shaking stops. In the absence of sturdy shelter like a table or desk, a person should remain in this position against an interior wall. During and immediately after an earthquake, elevators should be avoided; stairs are the safe route out of a building. These precautions reflect not panic but preparedness—the acknowledgment that while major earthquakes are unlikely in Brazil, understanding how to respond is always prudent.
Citações Notáveis
The possibility is very remote, because tremors larger than magnitude 7 occur at the limits of plates, not in their interior— George Sand, physicist and professor at University of São Paulo's Department of Geophysics
When the ground beneath a structure begins to vibrate, the building amplifies that motion upward, making the effect more noticeable at higher elevations— Marcos Ferreira, geophysicist at Brazil's Geological Service
A Conversa do Hearth Outra perspectiva sobre a história
Why did people in tall buildings feel this earthquake so much more than those on the ground?
The building itself acts as an amplifier. When the ground vibrates, the structure transmits that motion upward, and the effect becomes stronger the higher you go. It's not that the earthquake was stronger up there—it's that the building magnifies what's already happening below.
So the geology of São Paulo also played a role in who felt it?
Exactly. Certain neighborhoods sit on sedimentary basins—layers of rock and sediment that have accumulated over millions of years. These basins are like highways for seismic waves. A tremor that might be barely noticeable in one area can become quite obvious a few blocks away, depending on what's underneath.
Given that this earthquake released energy equivalent to 32 Hiroshima bombs, why is Brazil's risk so low?
It's all about location on the tectonic plate. The biggest earthquakes happen at the edges where plates collide and grind against each other. Brazil is in the middle of its plate, far from those boundaries. The Chilean earthquake happened right at the collision zone between two plates. That's where the real energy builds up and releases.
Has Brazil ever experienced anything close to what Chile just felt?
Not really. The strongest earthquakes Brazil has recorded were in the magnitude 6 to 6.8 range, and they happened in remote areas—Mato Grosso, Ceará, Acre. They caused minimal damage. A magnitude 7.4 in a populated area would be catastrophic, but the geological conditions that create those kinds of earthquakes simply don't exist here.
What should people actually do if they feel tremors?
Crouch down, protect your head and neck with your arms, and hold on until it stops. If you're in a building, stay away from elevators and use the stairs. It's simple, practical advice—not because we expect major earthquakes, but because being prepared costs nothing.