On Wednesday evening, Venezuela suffered the strongest shaking in more than 100 years, collapsing buildings and killing more than 100 people. According to the U.S. Geological Survey, the quake was a rare phenomenon known as a “doublet,” which involves not one but two major earthquakes.
A double earthquake occurs when two earthquakes of similar magnitude occur in succession and can cause more damage than a single earthquake. In this example, a magnitude 7.2 earthquake shook northern Venezuela, followed just 39 seconds later by a magnitude 7.5 earthquake.
“Double earthquakes are very destructive,” says Raul Pérez López, an earthquake scientist at the Spanish Institute of Geology and Mining in Madrid. “The main difference is that two earthquakes have similar energy, but a (single) earthquake and a (minor) aftershock have less energy.”
However, some researchers speculate that additional data in the coming days could reveal that the event was caused by one large earthquake rather than two. The difference between one long earthquake and twin earthquakes may not be significant in terms of human impact, but it could teach scientists a lot about this unusual phenomenon and predicting earthquake intensity.
“It’s probably going to take seismologists a few days or more to really figure this out,” said Judith Hubbard, a Cornell University earthquake scientist who analyzed the recent seismic activity. “After that, they may not have a definitive idea of, ‘Was it one earthquake or two earthquakes?'”
Although doublets are rare, this region is not unfamiliar with doublets. A weaker double earthquake (magnitudes 6.2 and 6.3) occurred there in September 2025, according to the USGS.
“We don’t really know much about which faults produce doublets and which faults don’t, or whether there are any types of faults that produce doublets,” Hubbard said. “It just doesn’t happen often enough to come up with a rule of thumb.”
Earthquakes occur when two moving plates come together, tension builds up, and the stored energy is suddenly released. Wednesday’s tremor occurred at the boundary between the Caribbean and South American plates, which continue to slide at a rate of about 20 millimeters a year. Although large and damaging earthquakes are common in northern Venezuela, only seven earthquakes of magnitude 6 or higher have occurred in the region in the past 100 years.
Hubbard said because of the quick succession of Wednesday’s earthquakes, preliminary data may make it difficult to confirm that there were two quakes. There are also other possible explanations for what scientists are currently seeing on seismometers.
First of all, large magnitude 7.5 earthquakes usually don’t happen all at once. These large earthquakes begin in one location, propagate along the fault, and rupture different parts at different times. In the case of Venezuela, the initial pulse that caused the magnitude 7.2 earthquake may have triggered a domino effect of pulses that turned into subsequent, larger earthquakes.
She said an earthquake typically takes about 30 to 40 seconds to complete, but “there was a much larger pulse within the shaking of the initial earthquake, which was very difficult to see with the current data.”
If these are two pulses from a single rupture, the event could be equivalent to a magnitude 7.6 earthquake, Hubbard said.
But in previous preliminary reports, the USGS mapped out two different quakes, about 5 to 10 kilometers (3 to 6 miles) apart, setting out the possibility that one caused the other. Despite the close proximity, authorities proposed that the fault behind the quake had shifted in an opposing motion.
“Seismic data is fuzzy,” Hubbard said. “Until we have more data, we won’t be able to tell the difference between the orientation of these two faults and the direction of slip.”
Several less strong aftershocks have since occurred near Caracas, which may shed some light on the situation. If aftershocks occur in a similar pattern to the initial tremors, it could confirm whether the proposed direction is accurate, she said.
As the damage spreads, it may be difficult to confirm what happened on the ground. Especially in the area around Caracas, underground sediments may have slowed and amplified the seismic waves, leading to an increase in their destructive power. Additionally, ground subsidence can cause further damage to the building’s foundation. The region lacks an extensive seismic network, and power outages at key sites could further delay efforts. Satellite data should be available within days and could reveal the fault’s movement and provide further clues about the ruptured fault.
Double earthquakes are rare, but when they occur they attract attention. In 2023, two earthquakes of magnitude 7.8 and 7.7 occurred in Türkiye and Syria. They occurred nine hours apart and caused widespread damage.
Hubbard hopes that this phenomenon will be actively studied in the scientific community and could help scientists better estimate how large an earthquake can grow in just the first few seconds of rupture.
“Everything we know about earthquakes comes from case studies of large earthquakes like this one,” Hubbard said. “Even with very little data, we were able to learn a lot.”
