What is causing successive earthquakes in Instagram-haven Santorini?

Santorini seems to be paying the price for its beauty. Its stunning cliffs and whitewashed villages remain precariously perched on shaky ground.

The island has been placed under a state of emergency after a magnitude 5.2 earthquake struck on Wednesday evening, the strongest in a series of tremors since late January.

Over the past week, thousands of near-constant earthquakes—ranging in depth from 5km to 25km—have been recorded in the region, according to a preliminary report by Türkiye’s disaster management agency (AFAD) and the Mineral Research and Exploration General Directorate (MTA).

Santorini sits atop an active volcanic arc in the southern Aegean along the Aegean Volcanic Arc, a seismically active region.

The island’s seismic events, shallow and confined to the Aegean plate, lack deeper seismic activity, suggesting that tectonic stresses are concentrated in the upper plate.

“The tides that occur in the South Aegean Sea, the African tides, are currently moving under the Anatolian tides throughout the Aegean-Cyprus arc,” Dr Naci Gorur, a Turkish seismologist, tells TRT World.

The earthquakes have been particularly clustered near the island of Amorgos, in a seismic belt that stretches from Athens to Bodrum and includes volcanic islands such as Milos, Santorini, and Nisyros. The Aegean Subduction Zone, where the African plate plunges under the Aegean, passes just south of this arc.

“These earthquakes are caused by small cracks under the sea. And of course, there is some energy loss with each crack. But it does not help to reduce the heat energy caused by these earthquakes,” Gorur says.

But do these smaller tremors help relieve pressure, preventing a larger and more devastating quake? Gorur is doubtful.

“It has a small impact. So, its energy loss does not reduce the energy caused by any of our real events. It does not make it ineffective,” he says.

The seismologist added that if a larger earthquake were to occur, its effects on Türkiye would be limited.

“We don't think that Türkiye will be affected by this,” he says. However, volcanic activity is another matter.

“If the development of tides and volcanism is directed towards Türkiye, or if it becomes a real volcanism. If it turns into a volcanic eruption, the ash that will flow from the sea and lava will affect Türkiye,” he says.

Gorur cautions that tsunamis could hit Türkiye’s coast and cause damage, but “to a certain extent.”

“These earthquakes are currently operating in the form of an earthquake storm,” he says. “Though it is mostly tectonic, it may have volcanic effects.”

Volcano or No?

Seismic activity in a region with a long history of volcanic eruptions raises concerns about a potential awakening of Santorini’s volcanoes, and whether or not the current quakes will trigger magma activity.

Greece is Europe’s most earthquake-prone country. Santorini is home to two volcanoes, fringing the Nea Kameni underground volcano, nestled within Santorini caldera and Kolumbo, which sits underwater about 8km (5 miles) northeast of the island.

The preliminary report by the Turkish disaster agency AFAD and the Mineral Research and Exploration General Directorate (MTA) acknowledges the complex relationship between tectonic and volcanic activity.

The report notes, “While seismic movements that develop in a magma chamber can occur, volcanism can also result as a result of tectonic movements.”

Gorur’s opinion concurs with the AFAD report that the plates mostly result from tectonic movement “but it may also have volcanic effects.”

However, history suggests that earthquakes do not necessarily lead to eruptions. The report makes the distinction that seismic activity of similar intensity as recorded in the same region during the course of 14 months between 2011-2012 did not lead to any volcanic activity.

Some experts believe there is insufficient magma in the chambers that sit deep in the volcano to warrant an eruption.

The last major eruption of the Santorini volcano known as Minoan eruption was destructive. It occurred around 3,500 years ago in 1600 BCE. Some historians have linked it to the collapse of the Minoan civilization on the island of Crete. The most recent, in 1950, wasn’t as cataclysmic.

The AFAD report states that volcanic activity depends on a variety of geological features “such as the type and intensity of the eruption, magma-water interaction and so on.”

The likelihood of another large eruption anytime soon remains unclear.

According to Efthymios Lekkas, a Greek seismologist who heads the scientific monitoring committee for the Aegean Volcanic Arc: We have a very long time ahead of us before we face a big explosion.