Earthquakes off Santorini

February 2 – The Greek authorities, including the Ministry of Climate Crisis and Civil Protection, have placed emergency services on the islands of Santorini, Amorgos and the wider region on alert after intense seismic activity has been occurring in the last few days.

Over the last 24 hours, 200 earthquakes have been recorded between Santorini and Amorgos, whilst today, dozens of seismic tremors continued, with three of them measuring greater than four on the Richter scale and the focal depth ranging from 4 to 10 kilometres.

Schools on Santorini will be closed tomorrow, Monday, as a precaution, while citizens are urged to avoid large gatherings in closed spaces. The same will apply to the islands of Amorgos, Ios and Anafi, as the area has significant faults and the possibility of a strong earthquake cannot be ruled out.

An emergency meeting has been held at the Maximos Mansion in Athens, chaired by the Greek Prime Minister to discuss the situation and to assess all emergency plans and the logistics required for any future eventuality.

Monday, February 3 – A storm of seismic tremors has continued in the sea area between Santorini and Amorgos in the last 24 hours, with 16 of the dozens of quakes being above four on the Richter scale.

Professor of Natural Disasters Costas Synolakis, University of Crete, confirmed: “No one can say with certainty what will happen. We are monitoring the evolution of the phenomena”.

On all the islands in the region, schools will be closed today, with citizens urged to avoid large gatherings in closed spaces and stay away from derelict buildings. Santorini is at specific risk as the island has many older buildings which were built before strict building codes came into force.

As a precaution, the Special Disaster Medicine Department of the Hellenic Emergency Medical Service is arriving on Santorini today, with a doctor, rescuers, an ambulance and special vehicles. Emergency equipment and vehicles are also being rushed to Amorgos and Ios to reinforce the equipment available on those islands.

The last major earthquake in the region occurred on July 9, 1956, in the early hours of the morning, with a magnitude 7.7 quake, the largest to be seen in Europe in the 20th century. It was followed by a tsunami 25 metres high. On Santorini, at least 53 people were killed and more than 100 were injured. Thirty-five percent of the houses collapsed and 45 percent suffered major or minor damage. Almost all public buildings were completely destroyed. The devastation was equally as severe on Amorgos and the other islands in the region.

An earthquake of 4.9 on the Richter scale occurred at 10.26 this morning (local time), Monday, February 3, 32 km northeast of Santorini and 19 km south-southwest of Amorgos at a focal depth of 2 km. This was followed by a quake at 11:30 (local time) of 5.0 located 25.4 km northeast of Santorini and at a focal depth of 2 km.

Although most on the islands are staying calm, as a precaution many have decided to leave until the situation improves. Yesterday, Sunday, flights and ferry routes from Santorini were fully booked. The same picture is being recorded today. Aegean Airways has added extra flights to cover the demand.

16:00 – The enormous seismic storm playing out in the marine area between the islands of Santorini and Amorgos shows no sign of abating with over 100 quakes in the last 16 hours.

Tuesday, February 4 – The seismic storm continues in the marine area between the islands of Santorini, Ios and Amorgos with over 550 tremors above magnitude 3 in the last three days.

A statement from the government’s Earthquake Planning & Protection Organisation yesterday confirmed that the intense seismicity in the region may continue for several “days”, if not “weeks”.

The Greek government is holding a number of meetings with local authorities, Fire Brigades, Police, the Coast Guard, the Armed Forces, health authorities and seismologists, to assess the situation and implement further plans if needed.

Schools, colleges and sports facilities will remain closed until at least Friday, February 7 on Santorini, Anafi, Ios and Amorgos.

The exodus of both residents and tourists from the islands by ferry and air continues, with around 9,000 having already left Santorini.

14:00 – Concern is growing regarding the situation in the Cyclades as tremors of 4 to 5 on the Richter scale have been occurring continuously all morning with the focus of the phenomenon moving towards the island of Amorgos. Although the situation could change at any time, scientists believe that the main sequence of earthquakes has yet to occur.

There is also increased focus today on the active undersea volcano Kolumbo, which lies around 8 km northeast of Santorini, with further seismic sensors being installed around the volcano’s submerged crater.

16:00 – The seismic storm continues to shake the Cyclades. At 15:04 (local time) a further quake was recorded, the first to reach 5 on the Richter scale. The quake occurred 27.5 km. NE of Santorini at a depth of 4 km.

As yet there’s been no sign of a de-escalation of the phenomenon, on the contrary, there has been an an increase in the frequency and magnitudes recorded today. Scientists are cautious about what the future will bring and continue to express their concerns.

Wednesday, February 5 – The seismic storm is continuing at an unrelenting pace, with over 165 tremors in the last 24-hour period, 24 of them measuring above 4 on the Richter scale with four being 5.0, 4.9 and 2 of 4.8. Scientists believe the potential for an earthquake of 6 or greater on the Richter scale still exists.

The exodus from Santorini continues with over 10,000 having now left the island out of approximately 15,550 permanent residents.

There is still no clear picture of how the situation will progress as the evolution of the storm so far has been unprecedented and unpredictable.

Thursday, February 6, 08:00 – The intense seismic activity continued overnight, including 7 earthquakes over 4 on the Richter scale occurring between 04:00 and 05:30 (local time) alone, with a 5.2 magnitude quake southwest of Amorgos during the night being the largest tremor so far.

Authorities are stressing that the risk of landslides on Santorini remains high, due to the special geological conditions of the island, with the Old Port, Port of Athinios, Fira, Armeni, Ammoudi and areas of Thirassia particularly at risk.

Friday, February 7 – The seismic storm has continued overnight with multiple quakes above 4 on the Richter scale. Due to both the intensity and uncertainty of the phenomenon, the General Secretariat of Civil Protection has declared a state of emergency on Santorini until March 3. Over 7,700 earthquakes have shaken Santorini in the last 10 days.

Scientists are trying to understand the evolution of seismic activity so far and whether even larger earthquakes can be expected in the future. They are also studying data to assess the possibility that the quakes will activate the underwater volcano Kolumbo, located 8 km northeast of Santorini.

However, the general opinion of scientists is that the seismic activity in the Cyclades will continue for the next few weeks with similar intensity.

Saturday, February 8, 08:00 – During the early hours of this morning, there were three stronger earthquakes in the sea area south of Amorgos of 4.1, 4.1 and 4.4 magnitudes. However, although overall, the seismic activity seems to be slowing, the situation still causes concern, as landslides pose a major threat to the islands, especially on Santorini.

Monday, February 10, 19:00 – The seismic storm that has been underway between the islands of Santorini and Amorgos continues for another day, including three more earthquakes of over 4 on the Richter scale.

Tuesday, February 11, 09:00 – During the night two strong earthquakes occurred in the sea area between the islands of Santorini and Amorgos. The first, of magnitude 5.3 (the strongest quake so far), occurred at 22:16 on Monday evening local time. The second struck at 00:37 and was recorded at 5 on the Richter scale, with eight further quakes of above 4 magnitude following in the early hours of this morning. Dozens of tremors below 4 magnitude rattled the islands during the night leading to those still on the islands spending another sleepless and frightening night.

A large scientific team is analysing data from seismographs installed on the islands and in undersea areas to determine whether the activity has any correlation between volcanic and tectonic changes.

From 26 January to 8 February, the Seismology Laboratory of the University of Athens registered more than 12,800 earthquakes in the Santorini-Amorgos region. The storm seems to be centred around the small rocky and uninhabited islet of Anhydros (Amorgopoula), located 37 km northeast of Santorini. A fault just off Anydros was the source of the devastating 7.6 magnitude earthquake in 1956 that nearly levelled Santorini.

Scientists have admitted that they are perplexed by the whole phenomenon, as it continues to be highly unstable and unpredictable, a situation never seen before.

To illustrate the dynamic state of the phenomenon, between 11:40 and 12:30 today (local time) there were 20 quakes that ranged from 2.4 magnitude to 4.7 magnitude, an average rate of one quake every 9 minutes.

Wednesday, February 12 – 08:00 – In the early hours of this morning an earthquake measuring 5 on the Richter scale struck in the sea area between the islands of Santorini and Amorgos, followed by 4 quakes all with a magnitude above 4. Over twenty tremors below magnitude 4 both directly preceded and followed these stronger quakes.

19:00 – Earthquakes continue to rock Santorini and Amorgos, with continuous tremors all day. Scientists are now stating that the phenomenon could last for weeks or even months.

Since January 26, more than 14,000 tremors have been recorded, while the government has decided to extend the emergency measures until at least Saturday, with schools remaining closed on the affected islands and people urged to avoid gatherings.

Thursday, February 13, 17:00 – The seismic storm continues today, with dozens of tremors ranging from 1.7 to 3.6 magnitude.

A state of emergency has been declared for the island of Anafi which lies around 20 km east of Santorini. The declaration which already exists for Santorini and Amorgos, has been imposed to address emergency needs and manage the consequences resulting from the ongoing seismic storm.

Friday, February 14, 08:00 – For the 22nd day, dozens of earthquakes continue to rock the Cyclades, a fact that is deeply concerning to scientists, who believe that the unprecedented phenomenon will now last for many more weeks and are not ruling out the possibility of a major earthquake of magnitude 6 or above in the area.

Regarding Nea Kameni, the volcano located in the centre of the caldera of Santorini, ongoing seismic measurements show that the volcano has not been unduly affected by the seismic activity leading scientists to believe that an eruption in the near future is unlikely.

The initial focus of the earthquakes was located near Santorini, but over time moved northeast towards the island of Amorgos. Now it appears that the focus is returning southwest back towards Santorini.

Sunday, February 16 – As the strong seismic sequence continues between the islands of Santorini and Amorgos and as indications are that there is a correlation between the seismic activity and the volcanoes of Nea Kameni on Santorini and the submarine volcano Kolumbo 8km to the north, the two committees of the Permanent Scientific Committee for Seismic Hazard Assessment and Seismic Risk Reduction and the Permanent Scientific Committee for Monitoring the Greek Volcanic Arc are meeting this morning in Athens at 09:00 to discuss the implications.

Data retrieved from seismic instruments placed in the epicentre of the activity strongly suggests to scientists that the seismic storm is originating from the volcanoes due to the intrusion of magma into the Anydros fault.

16:00 – The conclusion of the two committees of seismic hazard and volcanic arc held today is that although the seismic sequence is showing a relative decline in intensity, an increase in ground deformation observed in the wider area of ​​Santorini could be a sign of future volcanic activity. Monitoring of the whole area will continue.

Tuesday, February 18 – Although the frequency of tremors has reduced in the last two days, scientists have stated that they do not believe the seismic activity is showing signs of stopping, on the contrary, they believe that the activity will continue for some considerable time. It is suspected that the movement of magma is partly responsible for the ongoing seismic sequence, which could lead to a volcanic or undersea eruption of Nea Kameni or Kolumbo.

Due to the complex nature of the phenomenon and the inability to determine future developments, schools will remain closed until Friday, February 21 in Santorini, Ios, Anafi and Amorgos.

Thursday, February 20 – It has been confirmed by the government’s scientific committees that the level of tectonic activity between Santorini and Amorgos continues unabated. There will be a further meeting of the committees today to assess the latest data and decide whether or not to extend the emergency measures currently enforced.

With regard to Santorini, the seismic activity within the caldera remains constant, but increased ground deformation has been observed in the wider area of ​​Santorini caused by the continuing intrusion of magma deep below the island. However, scientists have stated that they do not believe this could lead to volcanic activity in the Santorini caldera or at the undersea volcano, Kolumbo, situated 8km northeast of the island.

Friday, February 21 – Due to the ongoing seismic activity, scientists are conducting a detailed study on Santorini to identify areas at high risk of landslides. Since January 26, there have been more than 21,500 earthquakes recorded in the region, of which 18,600 were above magnitude 1.0 on the Richter scale, with over 2,000 tremors of magnitudes up to 5.3 being recorded of which 14 had a strength of 5.0 or greater. The earthquakes have been concentrated mainly in an area 25 kilometres northeast of Santorini and 25 kilometres southwest of the island of Amorgos.

Sunday, February 23, 07:30 – Although tremors have continued overnight in the marine area between the islands of Santorini and Amorgos, with 14 in the last 6 hours, magnitudes only range from 1.6 to 2.7 on the Richter scale.

The government’s scientific committees have confirmed that data shows that the current seismic activity between Santorini and Amorgos is due to undersea tectonic faults that lie in a southwest-to-northeast direction, caused by a combination of tectonics and the deep movement of magma. Although the seismic activity has eased in the last few days, there is no indication that the phenomenon will cease anytime soon.

As a precaution, it has been confirmed that schools will remain closed until Friday, February 28, on the islands of Santorini, Ios, Anafi and Amorgos.

Monday, February 24, 18:00 – There has been a surge of 57 tremors in the last 18 hours in the marine area between Santorini and Amorgos, falling between the magnitudes of 1.1 and 4.4 on the Richter scale. However, the majority of tremors were below 2.8 magnitude.

Professor Efthymios Lekkas, head of the government’s Earthquake Planning and Protection Organisation, stated yesterday that the seismic activity on Santorini is expected to continue for at least several weeks, possibly even a few months.

Thursday, February 27 – As the frequency and magnitude of tremors have reduced in the last few days, residents of Santorini, who left due to the potential danger from the seismic phenomenon, are returning. From February 12 until yesterday, official figures show that 5,475 locals and workers have returned.

Sunday, March 2, 10:30 – The Greek government’s Permanent Special Scientific Committee for Seismic Risk Assessment and Seismic Risk Reduction, in collaboration with the Permanent Scientific Committee for Monitoring the Greek Volcanic Arc have confirmed that schools on the islands of Santorini and Amorgos will reopen on Tuesday, March 4, due to the significant reduction in seismic activity in the area. However, earthquake safety precautions will still be in place as the risk of aftershocks, whilst significantly reduced, has not been entirely eliminated. The last few days have also seen a growing number of residents continuing to return to the islands.

The University of Athens Seismology department has confirmed that more than 24,800 earthquakes have been recorded since the seismic activity began, with some exceeding a magnitude of 5.0 on the Richter scale.

So far today there have been 15 tremors, with the strongest being 2.8 magnitude. At the height of the activity, the region experienced over 300 quakes a day.

Thursday, March 6, 08:00 – Although the seismic activity between the islands of Santorini and Amorgos continues to ease, with 8 tremors so far today, the strongest being of magnitude 2.6, scientists remain cautious as the possibility of a strong aftershock cannot be ruled out.

The magma intrusion deep below the area, which has been one of the causes of the phenomenon, seems to be settling back into its original state, with ground deformations now diminishing.

Saturday, March 8, 12:00 – So far today there have been 20 light tremors in the marine area between the islands of Santorini and Amorgos, the strongest being of magnitude 2.6, with the majority being between 1 and 2 on the Richter scale.

Although the seismic activity continues to weaken, scientists are still advising caution due to the phenomenon’s unpredictability so far.

We will post information on any changes in the situation if and when they become available.

You may also like to read our Restless Earth article, which discusses Santorini’s Seismic history.