Residents and tourists on the Greek island of Santorini have been put on high alert after an increase in seismic activity.

Since Friday, the island has been hit by more than 200 tremors, including a 5.0-magnitude earthquake on Monday morning.

Local authorities have ordered schools to close and have advised residents and hotel owners to drain swimming pools as a precautionary measure.

Aegean Airlines has also put on two additional flights to and from Santorini – on Monday, February 3 and on Tuesday, February 4 – to help residents and tourists depart the island, following a request by the Greek Ministry of Climate Crisis and Civil Protection.

People on the island have reported tremors every few minutes at times. The strongest earthquakes occurred on the morning of Monday, February 3. A magnitude 5.0 earthquake struck just 20 miles off the coast of Santorini at 9.29am. An hour earlier, a magnitude 4.9 earthquake occurred 19 miles off Santorini, according to the United States Geological Survey.

What is happening in Santorini right now?

A series of tremors exceeding a magnitude of 4.0 have struck close to the Aegean tourist island of Santorini since Friday, January 31. The quakes are ongoing as of Monday, February 3.

While there have been no reports of casualties or damage to buildings at the time of writing, Greek authorities have advised all schools to be closed on Monday, February 3. Schools on the neighbouring islands of Amorgos, Ios and Anafi will also be closed.

Residents with swimming pools and hotel owners have been advised to drain their swimming pools. This is because, in the instance of a high-magnitude earthquake, large quantities of water could potentially damage or destabilise nearby buildings.

People have also been advised to avoid large open-air gatherings, to avoid entering old buildings, and to stay away from four small ports on the island, including the popular harbour town of Fira where cruise ships dock.

Tents have been erected in an outdoor stadium, and special disaster response units have been put on standby as a precautionary measure.

“We estimate it (the activity) will continue for some days and there could be a lengthy seismic sequence,” Efthymios Lekkas, a professor of tectonic geology and disaster management, said on Greek television.

Costas Papazachos, a professor of geophysics and seismology, said the worst-case scenario would be an earthquake measuring 6.0.

“This does not necessarily mean that there will be a strong earthquake, it may well be that the thermal energy dissipates and we have a smaller earthquake in Santorini… But we have to take measures,” he said in an interview with the Greek website protothema.gr.

Does Santorini have a history of earthquakes?

Greece is positioned at the junction between European and African tectonic plates. As a result, earthquakes and tremors are regular occurrences.

In 1956, a magnitude 7.7 earthquake occurred off the island of Amorgos, causing significant damage on the island and neighbouring Santorini.

It was followed minutes later by a 7.2 magnitude earthquake, closer to Santorini. This was the largest quake in Greece in the 20th century, prompting a 30m tsunami and causing the deaths of 53 people across Amorgos and Santorini, with more than 100 people injured. More than 500 houses were destroyed in the earthquake, with many more badly damaged.

The island of Crete has suffered a series of high magnitude earthquakes in recent years. In 2013, 2020 and 2021 the island has suffered earthquakes with magnitudes in excess of 6.0.

Santorini is a volcanic island, curving around a flooded caldera.

The island, as it is recognised today, formed following the Minoan volcanic eruption of 1600BC, one of the largest in human history. The last time the volcano erupted was in 1950, although this was relatively small and the chances of a major eruption are slim. The island witnesses a large explosion only once in every 20,000 years, and the last one was only 3,500 years ago.

Sources: The Telegraph