The Greek government has declared a state of emergency on the island of Santorini as the region experiences a relentless series of earthquakes. The “earthquake swarm,” which began as minor tremors in late January, has escalated into a significant seismic event, shaking the island multiple times a day. The tremors are also affecting nearby islands in the Aegean Sea, with some quakes occurring just minutes apart.
Escalating Seismic Activity
Over the past two weeks, seismologists have recorded thousands of earthquakes, with as many as 30 daily exceeding magnitude 4.0. The largest so far, a magnitude 5.1 quake on February 6, was felt in Athens, Crete, and even parts of Turkey, more than 240 kilometers away. The earthquakes, occurring at depths of less than 10 kilometers, are shallow enough to be strongly felt by residents and have already caused rockfalls along coastal cliffs and minor structural damage to vulnerable buildings.
As fears of a potential volcanic eruption grow, Santorini a world-renowned tourist destination has seen a mass exodus. More than 11,000 people, including tourists and locals, have fled the island in the past week, leaving it eerily empty.
Understanding the Earthquake Swarm
Greece is one of Europe’s most seismically active regions, with a long history of significant earthquakes. The current swarm is concentrated near Anydros, an uninhabited islet 30 kilometers northeast of Santorini. This region is part of the Hellenic subduction zone, where the African tectonic plate slowly moves beneath the Eurasian plate. The seismic activity appears to align with known faults between Santorini and Amorgos rather than indicating magma movement beneath Santorini itself.
Local scientists have assured that there are no signs of volcanic unrest on Santorini, whose last eruption occurred in the 1950s. However, nearby faults have a history of producing powerful quakes. In 1956, a magnitude 7.8 earthquake in the region triggered a tsunami and caused significant destruction, followed by a magnitude 7.2 aftershock. Over 53 people lost their lives, and many more were injured.
A Swarm, Not a Mainshock
Seismic activity typically follows one of two patterns: the mainshock-aftershock sequence, where a large earthquake is followed by diminishing aftershocks, or an earthquake swarm, where multiple quakes of similar size occur over an extended period. The 1956 quake was a classic mainshock-aftershock event, but the current activity near Santorini, featuring thousands of similar-magnitude quakes, is characteristic of an earthquake swarm.
Swarms are often linked to fluid movement deep within the Earth’s crust, and while they typically produce less destructive quakes, they can persist for days, weeks, or even months. The unpredictability of such swarms makes them challenging to forecast.
What Comes Next?
While only about 5% of earthquake sequences serve as foreshocks to larger events, the possibility of a stronger and more damaging earthquake cannot be ruled out. Seismologists warn that the swarm could continue for an extended period, fluctuate in intensity, or even trigger a larger quake. Authorities are closely monitoring the situation, urging residents to remain cautious and prepared.
As uncertainty looms, Santorini and its neighboring islands brace for what may come next, hoping the shaking subsides before any further damage is done.