Venezuela’s deadly ‘doublet’ earthquakes may have been a single big one. Here’s why it matters

By Kasha Patel, CNN

(CNN) — On Wednesday evening, Venezuela was hit with its largest tremors in more than a century — toppling buildings and claiming more than 100 lives. The event, according to the US Geological Survey, was a rare phenomenon called a “doublet” that contained not one but two major earthquakes.

Doublets occur when two quakes of similar magnitude happen in close succession — potentially causing more damage than a single quake. In this instance, a 7.2-magnitude earthquake shook northern Venezuela and was followed by a 7.5-magnitude quake only 39 seconds later.

“Double earthquakes are very destructive,” said Raul Perez-Lopez, an earthquake scientist at Madrid’s Geological and Mining Institute of Spain. “The main difference is that double earthquakes have similar energy, whereas (a) single earthquake and (smaller) aftershocks are lesser in energy.”

Yet some researchers speculate additional data over the coming days could reveal that the event was caused by one large earthquake instead of a duo. The difference between one long earthquake and a twinned pair may not matter in terms of human outcomes, but it could teach scientists a lot about this uncommon occurrence and predicting the severity of earthquakes.

“It’s going to take probably some days or longer for the seismologists to really piece out the event,” said Judith Hubbard, an earthquake scientist at Cornell University who analyzed the recent seismic activity, “and then they may not have a conclusive idea of, ‘was it one earthquake or two earthquakes?’”

Doublets are rare, although this region isn’t a stranger to them. A weaker doublet — 6.2- and 6.3-magnitude earthquakes — struck there in September 2025, according to USGS.

“We don’t really have a good sense of which faults produce doublets and which ones don’t — or whether there even is a fault type that produces doublets,” Hubbard said. “They don’t happen frequently enough for us to be able to come up with a rule of thumb.”

Earthquakes occur when two moving tectonic plates become stuck, build tension and then suddenly release the pent-up energy. Wednesday’s tremors occurred on the boundary between the Caribbean and South American plates, which have been slipping at a rate of around 20 millimeters per year. Northern Venezuela often experiences large, damaging earthquakes, but, over the past century, the region has only experienced seven earthquakes of magnitude 6 or greater.

Because of the quick succession of Wednesday’s quakes, Hubbard said confirming there were two earthquakes could be difficult with the preliminary data — and there are other possible explanations for what scientists see on seismographs currently.

For starters, a large 7.5-magnitude earthquake doesn’t typically happen all at once, she said. Such a major quake starts at one location and propagates along the fault, rupturing different parts at different times. In Venezuela’s case, the first pulse — responsible for the 7.2 quake — could have triggered a domino effect of pulses that turned into the larger sequel.

She said an earthquake takes about 30 to 40 seconds to complete usually, but “because that larger pulse happened inside the shaking of the first one, it was really hard to see” in the current data.

If these were two pulses of a single rupture, Hubbard said the event could be equivalent to a magnitude-7.6 quake.

In the preliminary reporting so far though, USGS painted a picture of two distinct quakes about 5 to 10 kilometers (3 to 6 miles) apart — setting up the possibility that one triggered the other. Despite the proximity, the agency proposed that faults behind the quakes slipped with opposite motions.

“The seismic data is ambiguous,” said Hubbard. “You can’t tell the difference between these two fault orientations and slip directions” until more data comes in.

Several, less intense aftershocks have since occurred near Caracas, which could provide clarity. If the aftershocks are rupturing in similar patterns as the initial tremors, she said it could confirm if the proposed orientations are accurate or not.

Confirming what happened on the ground could be tricky amid the damage. Especially in the area around Caracas, underground sediments may have slowed and amplified seismic waves, leading to increased destructive power. In addition, sinking ground could lead to additional damage to building foundations. The region lacks extensive seismic networks, and power outages in major hubs could further delay efforts. Satellite data, which should be available in the coming days, may reveal the fault movements and offer more clues about the faults that were ruptured.

Despite being rare, doublet earthquakes spark attention when they happen. In 2023, a pair of 7.8- and 7.7-magnitude earthquakes struck Turkey and Syria. They occurred nine hours apart and caused widespread damage.

Hubbard expects this event will be heavily studied in the scientific community and could help scientists better estimate how big an earthquake could grow just from the first few seconds of a rupture.

“Everything we know about earthquakes comes from case studies of large earthquakes like this one,” said Hubbard. “Even when there’s very little data, we’ve managed to learn a lot of things.”

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