The idyllic Greek island of Santorini, renowned for its postcard-perfect scenery, has been shaken—literally—by thousands of earthquakes in the past week. Residents and authorities are grappling with an "unprecedented" seismic swarm, raising concerns about how long this crisis might last.
A Community on Edge
"We've put all our mattresses in the living room," says Georgia Nomikou, a Santorini resident. She, like many others, fears the impact of the relentless tremors.
About 75% of the island's 15,000 residents have already evacuated following Wednesday's 5.2-magnitude quake—the most powerful recorded so far. Authorities declared a state of emergency as aftershocks continued into Thursday. Scientists remain puzzled by the pattern of these quakes, which don’t follow the usual mainshock-aftershock sequence.
What’s Happening Beneath Santorini?
Experts agree that the island is experiencing what Greece's Prime Minister has described as an "extremely intricate geological phenomenon."
"This is truly unprecedented. We have never seen anything like it in modern times in Greece," says Dr. Athanassios Ganas, research director at the National Observatory of Athens.
Santorini sits on the Hellenic Volcanic Arc, a chain of islands shaped by volcanic activity. However, it hasn’t experienced a major eruption since the 1950s, making the current seismic activity all the more perplexing.
Dr. Ganas explains that the crisis began with signs of volcanic unrest last summer. Then, in January, a surge of minor earthquakes was detected. In the past week, this activity has escalated into thousands of tremors, with no clear end in sight.
"We are in the middle of a seismic crisis," he states.
Dr. Margarita Segou of the British Geological Survey describes the tremors as occurring "in pulses." This swarm-like behavior means that when a larger quake—such as a magnitude 4—strikes, seismic activity intensifies for one to two hours before temporarily subsiding.
How Long Will It Last?
The big question remains: when will this stop? Unfortunately, experts cannot say for sure.
Seismologists hope that Wednesday’s 5.2-magnitude quake will be the largest, but there are no guarantees. Authorities have warned that the activity could persist for weeks.
Another concern is whether these tremors are foreshocks—precursors to an even larger earthquake—or if they are a self-contained seismic event.
"Some large earthquakes do experience foreshocks, with elevated levels of smaller quakes before the main event," says Professor Joanna Faure Walker of UCL’s Institute of Disaster Risk Reduction. However, Dr. Ganas clarifies that these are not volcanic earthquakes, as they lack the characteristic low-frequency waveforms typical of volcanic activity.
Dr. Segou and her team have analyzed past earthquakes in the region using machine learning to identify patterns from similar events in 2002 and 2004. While those quakes were weaker than the current ones, their "signatures" might offer clues about what to expect.
A City on Alert
To help manage the crisis, additional police units and military forces have been deployed to Santorini. Many residents, like Nomikou and her family, remain on edge, keeping small bags packed in case they need to evacuate at a moment’s notice.
Yet, not everyone is alarmed. Chantal Metakides, a lifelong Santorini resident, remains steadfast.
"I'm not afraid at all," she says. "For 500 years, this house has lived through earthquakes and volcanic eruptions, and it’s still standing. There’s no reason why this should change."
As scientists work to unravel the mystery of Santorini’s seismic activity, residents and tourists alike must brace for more uncertainty in the weeks ahead.
