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A prolonged earthquake swarm that struck the Greek islands of Santorini, Amorgos, and Anafi in January 2025 has been attributed to large-scale magma movement deep beneath the region, according to a study published this week in "Science."
The findings offer a detailed explanation for the tens of thousands of earthquakes recorded during the event, many of which exceeded magnitude 5.0 and were widely felt across the Aegean.
The seismic activity, which persisted for several weeks, prompted a wave of departures by tourists and heightened concern among residents.
Local authorities temporarily closed schools and increased monitoring of the nearby Kolumbo submarine volcano amid fears of potential volcanic activity or a recurrence of the destructive 1956 Amorgos earthquake.
In the study, an international team of researchers produced the first high-resolution three-dimensional map of the crust beneath Santorini using advanced seismic analysis supported by artificial intelligence.
The scientists treated individual earthquakes as “virtual sensors,” using their wave patterns to track stress changes and structural deformation in real time.
“The earthquakes effectively acted like instruments transmitting information from several kilometers below the surface,” said co-author Anthony Lomax. “The patterns we observed were consistent with lateral magma movement.”
The research indicates that the swarm was caused by magma migrating through a horizontal channel roughly 30 kilometers (18.6 miles) in length, located more than 10 kilometers beneath the seafloor.
The magma volume involved was estimated to be equivalent to approximately 200,000 Olympic-size swimming pools.
As the molten material advanced, it fractured overlying rock layers, generating the dense sequence of seismic events.
Scientists report that the swarm has now diminished. According to geophysicist Stephen Hicks, the magma appears to have stalled at a depth of about 8 kilometers.
“Magma can rise quickly, but with activity now paused, it is most likely cooling and remaining in place,” Hicks said.
Despite this assessment, experts caution that volcanic systems may undergo long, irregular phases of unrest.
Recent developments in Iceland were cited as a reminder of the unpredictable nature of such environments.
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