Is the Earth shaking more? Seismologists say no - critical summary review

The weeks that set off the alarm

On 24 June, two large earthquakes, of magnitudes 7.2 and 7.5, hit Venezuela seconds apart. At the end of July, a 7.1 shook southern Japan. On 10 August, a 7.4 was recorded in Colombia — considered one of the country's worst in the last 50 years, felt in Cali, Pereira, Manizales and Bogotá, with more than 200 dead. Five days later, a 7.7 struck the island of Flores, in Indonesia. Then the ground moved in Granada, Spain, with a much smaller 4.8, and again in Andalusia days later. Peru added a 7.2, felt from the Amazon to the central highlands, according to the country's Geophysical Institute (IGP).

The toll made the sequence impossible to ignore: the June earthquakes in Venezuela killed at least 6,301 people and destroyed thousands of buildings. Within weeks, the same question was circulating in several countries at once — has the planet entered a more active phase? — and seismologists in Spain, Chile, Colombia and the United States came out, almost simultaneously, to answer it.

What the catalogue actually shows

The short answer from the researchers is that there is no evidence of a phase of greater global tectonic activity. Temporal proximity does not imply that the events are physically related.

The baseline number is the one that settles most of the argument. In an update published in February of this year, the United States Geological Survey (USGS) estimates, from long-term records, around 16 earthquakes of magnitude 7 or above per year — roughly one every three weeks. That average lives with wide swings: by the USGS's own count, 2010 had 23 large earthquakes and 1989 had six.

María Belén Benito Oterino, a professor at the Polytechnic University of Madrid, compares it to tossing a coin in an analysis republished by Brazilian outlets: several heads in a row do not mean the coin has changed. Statistical analyses of the global catalogue of magnitude 7 or greater, she writes, show that the apparent global clusters can be explained by random variability together with local aftershock sequences.

What did change is our capacity to observe. The USGS's National Earthquake Information Center locates about 20,000 earthquakes a year, roughly 55 a day, and its catalogue registers more events largely because there are more instruments detecting them. Records from the early decades of the 20th century do not have the same coverage, so comparing the extremes of that series can turn a technological advance into an apparent geological change. The British Geological Survey makes the same point: people notice the busy stretches and do not notice the quiet ones.

Arancha Izquierdo, a seismologist with Spain's national seismic network, puts the perception problem plainly: "If for months no earthquake above magnitude 7 is recorded, we don't ask ourselves the same question." Arturo Belmonte, a researcher at the University of Concepción, in Chile, adds the media layer: "Today the news is instantaneous, so there is much more information."

When two earthquakes really are connected

Zoom in, and the picture changes. After a large earthquake it is normal for many smaller ones to follow in the same region — aftershocks — because the main rupture alters stresses in the surrounding rock.

A distinct case is the seismic pair, two earthquakes of comparable magnitude with nearby epicentres and a short interval between them. The Venezuelan doublet is an example. US seismologist Suzan Van der Lee, of Northwestern University, explained that both could be considered a seismic doublet, possibly within the same fault system, with the first slightly modifying local stresses and helping to trigger the second. The mechanism has a name: Coulomb stress transfer.

It does not travel. Static stress changes fall off quickly with distance and mostly affect the area near the rupture — which is why a possible link between the two Venezuelan earthquakes says nothing about the one in Colombia. Van der Lee noted that earthquakes recorded on the same day in Venezuela, Japan and the United States occurred at different tectonic boundaries and responded to independent geological processes. Belmonte still counsels caution locally: "When there is a seismic event, in the next 24 hours you have to be careful." In Indonesia, an aftershock came two days later.

Carlos Alberto Vargas, of the Geosciences Department at the National University of Colombia, offers another image: "You have two wooden boards under stress. One will break, and it is not necessarily the cause or the effect of the other."

Why South America shakes so much

Colombian seismicity is not an accident of geography. The country sits where the Nazca, South American and Caribbean plates interact. "The plates converge at constant speeds, but they have asperities that sometimes stop them moving freely," Vargas says. The national seismic network, with 85 sensors, detected 23,774 earthquakes last year, most of them imperceptible. The Bucaramanga seismic nest alone produces around 40 a day — "the second most energetic in the world," according to Vargas — though it was unrelated to the 10 August event.

That event was deep: about 100 kilometres down, at San José del Palmar, Chocó. Izquierdo explains the consequence with a simple image: "If you throw a stone into the water and you are far away, the circle it covers is much bigger." A deep earthquake spreads its waves over a wider radius, with the energy arriving more damped — which is why it was felt across an enormous area with lower intensity. Venezuelan earthquakes tied to the lateral boundary between the Caribbean and South American plates are very shallow, which explains their greater local destructive power. Peru's 7.2 came from the subduction of the Nazca plate, one of the fastest convergences in the world.

Magnitude alone does not determine impact, Benito Oterino writes: two similar earthquakes can have very different consequences depending on depth, distance from populations, terrain characteristics and, above all, the vulnerability of buildings and infrastructure.

Why no one can predict an earthquake

Science can say where earthquakes will happen. Not when. The USGS states that "neither the USGS nor any other scientist has ever predicted a major earthquake," and does not expect to know how to in the near future.

The obstacle is depth. Plates are between 10 and 250 kilometres thick; the deepest hole ever drilled, the Kola Superdeep Borehole in Russia, reached 12,262 metres. Seismometers, GPS and surface deformation measurements capture only indirect signals. Nor is there a consistent precursor: an editorial in Nature Computational Science notes that factors once thought to be linked to tremors — a rise in radon in water sources, anomalous animal behaviour — have little evidence behind them, and many earthquakes occur with none of them.

What is possible is statistical: the probability of an earthquake of a given magnitude on a specific fault within a window of decades or centuries. And once a rupture has begun, sensors can detect the faster, less destructive P waves and issue automatic alerts seconds or minutes before the destructive S waves arrive — enough to stop trains and shut down gas pipelines.

Two months later, La Guaira

The statistics say nothing about what happens after. In La Guaira, the Venezuelan state hit hardest in June, the governor, José Alejandro Terán, reported on 23 July that a first census found only 1,752 businesses operating out of the nearly 7,000 that existed before. The World Bank estimates direct damages there at 4.982 billion dollars. A survey by the local chamber of commerce found an 80% fall in income in the productive sector; economist Asdrúbal Oliveros projects that economic activity could contract between 55% and 70% in the third quarter of 2026 compared with 2025. More than 15,000 people worked in tourism-related activities before the earthquakes; that flow has practically disappeared, and the businesses that reopened now serve police officers, rescue teams and families still searching for relatives.

What to do with this information

The next time several strong earthquakes dominate the news in a few weeks, the useful reflex is not to connect the dots but to check them against the baseline. Around 16 magnitude 7-plus earthquakes a year, per the USGS, means clusters are expected; a run of them in a month is not, on its own, evidence of a planetary wave. And the reason the recent sequence felt exceptional, Benito Oterino argues, is not an unusual rise in seismic activity but the fact that several of these earthquakes hit populated areas and caused significant damage — if the same events had occurred in uninhabited regions, they would have drawn far less attention.

That shifts the question worth asking. Not whether the Earth is shaking more, but whether the cities in the way — Cali, Manizales, Caracas, La Guaira — are built for tremors that local geology has always anticipated, even if no calendar can. Vargas argues that public policy should not be "merely reactive" after a disaster, but a constant effort with continuous adjustments. Izquierdo frames it as a matter of where risk is produced: it is not enough to try to anticipate the unpredictable, "but to accept that vulnerability is built on the surface" — which means permanently funding the institutions responsible for disaster prevention and response.

And this is not a Latin American peculiarity. Asked about it, Izquierdo says: "You would be surprised to find countries that, right now, may be much worse prepared than several countries in the Americas."