Santorini: Increased seismic activity alerts scientists and citizens; preventive measures

Greek authorities have called on residents and visitors of the islands of Santorini and Amorgos to stay alerted due to increased seismic activity in the area. Seismologists and citizens are concerned.

Over 250 earthquakes have occurred in the area between Amorgos and Santorini since January 24, while over 100 minor tremors with increasing magnitude have reportedly occurred in the last 24 hours.

The seismic activity in the area is intense, with weak tremors ranging between 2-3 on the Richter scale.

Following an emergency meeting on Saturday, Minister for Civil Protection and Climate Crisis, Vassilis Kikilias, announced a series of preventive measures including the closure of schools for Monday, February 3, 2025.

Civil Protection Measures

• Schools closed on 3 February
• Avoid large indoor gatherings
• Avoid the ports of Amoudi and Old Port (Paleos Limenas) in the area of Fira (Santorini)
  

ΑΝΑΚΟΙΝΩΣΗ

Λόγω της σεισμικής δραστηριότητας των δύο τελευταίων 24ωρων στο θαλάσσιο χώρο μεταξύ της νήσου Θήρας και της Αμοργού, ο πρόεδρος του ΟΑΣΠ, Καθηγητής Ευθύμιος Λέκκας συγκάλεσε σήμερα το απόγευμα κοινή συνεδρίαση των δύο Επιτροπών (της Μόνιμης Eπιστημονικής Eπιτροπής…

— Vassilis Kikilias (@Vkikilias) February 1, 2025

The decision follows a meeting with government officials after increased tremors were recorded near the sea between Santorini and Amorgos.

The strongest earthquake had a magnitude of 4.5 on the Richter scale on Sunday morning, February 2, 2025.

Authorities have clarified that the tremors are linked to tectonic movements, not to volcanic activity.

The crater Kolumbos in red circle. It should be recalled that the catastrophic Santorini volcano eruption in 1600 BCE and a megatsunami that followed eliminated the Minoan civilization.

The seismic activity is being closely monitored, while further measures may be taken if necessary, seismologist Gerasimos Papadopoulos told ANT1 TV on Sunday.

Lekkas: Maybe a bigger earthquake but not a 7.6 R like in 1956

Speaking to media, professor of Dynamic Tectonics, Applied Geology and Natural Disaster Management at the National University of Athens and head of Earthquake Prevention and Protection, Efthymios Lekkas warned:

“We may have a bigger earthquake, but not like the one in 1956 with a magnitude of 7.6 R. The earthquakes are in the underwater area and have nothing to do with the Santorini volcano.

At the same time, Lekkas emphasized the need for preparedness due to the continuous earthquakes in the area in the last 24 hours.

Several earthquakes have been occurring in the islands group of the Cyclades since Sunday morning, February 2. According to the recordings of the Geodynamic Institute of the National Observatory, two seismic tremors measuring 4.5 and 4.1 on the Richter scale, had their epicenter southwest of Amorgos.

“The earthquake occurred between Amorgos and Santorini, and the largest tremor between these two islands is determined by the point where the epicenter is. If the epicenter is in Santorini, then Santorini, if the epicenter is in Amorgos, then Amorgos. The tremors are generally small,” Lekkas told newsit.gr.

He pointed out that over 100 seismic tremors have occurred in the Cyclades in the last three 24 hours, but they are of small magnitude.

“The earthquakes in Santorini are in the underwater area and have nothing to do with the volcano, but because we had a history with the great earthquake of ’56, which was a big earthquake of 7.6 on the Richter scale, we are in a certain state of readiness, but not because we are expecting such a big earthquake, but we must be in a state of readiness,” Lekkas noted.

Seismic Activity on Sunday morning

According to the Geodynamic Institute, in the wider area between Amorgos and Santorini, where the small island of Amidros is located, more than 20 tremors have been recorded since the dawn on Sunday, February 2. The largest reached 4.5 R at 9:22 while a tremor with 4.1 R occurred at 08:48 in the same area.

Seismologists said that there are essentially ground vibrations caused by the violent rupture of the earth’s rocks as a result of the action of tectonic forces of compression and tension. They are, moreover, the most common ones observed. In contrast to volcanic earthquakes, which are ground vibrations that either precede or accompany volcanic eruptions, and constitute 7% of all surface earthquakes.

Seismic activity in the Santorini Caldera

In an article on the website atlantea.news, Professor of Seismology at the Aristotle University of Thessaloniki and chairman of the board of directors of the Institute for the Study and Monitoring of the Santorini Volcano (IMPIS), Costas Papazachos presented recent data on the seismic activity in the area, including  the possibility of a major earthquake.

He clarified, however, that residents (incorrectly) combine the seismic outbreak with the recent announcement by the Civil Protection.

He recalled that the seismovolcanic crisis  has been ongoing since mid-September 2024 inside the caldera.

1. Where is the seismic activity, in Santorini or in Colombo [volcano crater]?

Two different phenomena are currently occurring in Santorini:

We have seismic activity within the caldera of Santorini with small earthquakes (with magnitudes up to ~4), mainly on the Kameni fault, from Palea Kameni to Fira. This seismicity is due to deformation of the northern caldera of the volcano, while both phenomena have been detected in a timely manner by the IMPIS networks, which was the first to inform the Greek State. The phenomenon (which is still ongoing) is similar to that of 2011-2012, that is, it is due to the same volcanic center, and it is evolving like the previous one, that is, relatively slowly (over a period of many months).

In the Anidros area we have an intense seismic sequence, which began on the afternoon of January 26, 2025 and continues until the hour. This sequence is in the faults of the Anhydra basin, although the uncertainties do not allow us to say in which (or which) exact faults it is.

2. Could we have two phenomena in progress together? Is it a coincidence?

The reality is that we do not know for sure. We know that the same forces that cause active tectonics (faults) are also related to volcanic centers. However, even if there is some distant connection, practically the two phenomena are independent in their evolution, one volcanic (in the caldera) and the other tectonic (in Anhydra).

3. In recent days I have not seen earthquakes in the caldera. Has the deformation in the caldera area stopped?

After the most powerful earthquake of January 25, 2025 (M=3.8) inside the caldera, we have a recession in seismicity. Although we are not sure, it is possible that this decrease in seismicity is temporary, as it was in 2011-2012 in the months of July-September. The main reason is that the other quantities we monitor (deformation, temperatures, etc.) have not visibly changed.

UK Travel Advice

Meanwhile, the UK has alerted its citizens who want to travel in the area.

Read our latest #travel #advice for #Greece with information about #seismic activity and #guidance about what to do before, during and after an #earthquake. https://t.co/uBcqTs3J2s

— UK in Greece (@ukingreece) February 1, 2025

This was retweeted by the UK Embassy in Athens.