Santorini ongoing earthquake swarm

The ongoing swarm of earthquakes near Santorini continues to baffle scientists, keeping disaster risk management teams and equally people in general high alert and suspense. News of the seismic activity has spread worldwide. Santorini - essentially a massive volcanic caldera with two small islets at its submerged center - has a long and turbulent volcanic history spanning 650,000 years. It has witnessed catastrophic eruptions, including a cataclysmic blast around 1560 B.C. that contributed to the collapse of a civilization, a major explosion in A.D. 726, and even a moderate eruption in 1950. As part of an active volcanic system, it remains a region of concern. Since January 31, 2025, seismic activity has surged across a 2,50 km² area northeast of Santorini, in proximity to the fault believed to be responsible for the July 9th, 1956 Amorgos earthquake and tsunami (Okal et al., 2009; Leclerc et al., 2024), raising further alarm. Amid ongoing seismic activity, the situation underscores the vital role of the UNESCO-IOC Intergovernmental Coordination Group for the Tsunami Early Warning and Mitigation System in the North-Eastern Atlantic, the Mediterranean, and Connected Seas (ICG/NEAMTWS).

A report dated February 9, prepared by Prof. Ahmet Yalciner and a team of experts and shared among scientists and UNESCO-IOC, highlighted seismic data from the National Observatory of Athens (NOA). The data indicated that over 1,200 earthquakes, with magnitudes ranging from 1.0 to 5.2, occurred between January 25 and February 7, 2025 (10:00 TS). The report is continuously being updated.

Of these, 129 had magnitudes of greater than 4.0, with the strongest recorded at ML 5.2 magnitude . Most of the earthquakes had focal depths between 10 and 15 km. The current earthquake swarm has formed a large NE-SW trending cluster east of Anydros Island (Figure 1a-b). Reports indicate that this seismic activity is occurring within the Anydros Uplift (Anydros Horst), situated between the NW-dipping Anydros Fault and the SE-dipping Santorini-Anafi Fault. Analysis of temporal variations in earthquake magnitudes and frequency suggests that magnitudes increased during the early phase of the swarm.

In the same report tsunami scenarios that may occur according to different mechanisms in the region between the tectonically and volcanically active islands of Santorini, Amorgos, Astypalaea and Anafi were examined with the help of tsunami numerical modeling. The effects of possible tsunami events that may occur due to each scenario focused on their effects on the Aegean Sea coast of Türkiye.

Clearly, there are different school of thoughts on the cause and triggering mechanisms and more monitoring and research will support consensus on the matter.

Denis Chang Seng, UNESCO-IOC Programme Specialist / Technical Secretary of ICG-NEAMTWS pointed out that aside the scientific discussions- about causes, a key interest which will need to be closely examined by the Disaster Risk Management and Response community is the self-initiated evacuation by residents of Santorini Island. Risk perception and human behavior play a crucial role in such situations, influenced by multiple factors, including proximity to perceived hazards, personal experience with natural disasters, and trust-or lack of trust-in authorities and experts. While cultural and individual factors such as media coverage, age, gender, education, income, and social status may not be the primary drivers of risk perception, they can act as mediators or amplifiers of the core relationships between experience, trust, perception, and preparedness to take protective action.

According to BBC news, as of February 6, more than 11,000 people have already left Santorini, with approximately 7,000 departing by ferry and 4,000 by air in response to the escalating situation, Greece declared a state of emergency on Santorini on February 5, following a 5.2-magnitude earthquake recorded at 21:09 local time (19:09 GMT) on Wednesday between the Greek islands of Amorgos and Santorini. The emergency decree will remain in effect until March 3 to "address urgent needs and manage the consequences." The Greek Prime Minister Kyriakos Mitsotakis reassured the public, stating, "All plans have been implemented. Forces have been moved to Santorini and the other islands so that we are ready for any eventuality." Despite the heightened seismic activity, no major damage has been reported on the island so far.

Amid the ongoing seismic activity, the complex and uncertain situation is highlighting the critical role, value, and benefits of the UNESCO-IOC Intergovernmental Coordination Group for the Tsunami Early Warning and Mitigation System in the North-Eastern Atlantic, the Mediterranean, and Connected Seas (ICG/NEAMTWS). The ICG-NEAMTWS plays a vital role in coordinating and managing tsunami risk related affairs across 40 Member States with access to the north-eastern Atlantic and connected seas, including the Mediterranean, Baltic, North, and Black Seas. The current operational system is designed and set up for seismic driven tsunamis and not. non -seismic tsunamis (volcano eruptions, landslide etc.), although efforts are underway to address the matter.

To enhance coordination and communication, the UNESCO-IOC Technical Secretary of ICG-NEAMTWS has requested the ICG-NEAMTWS Steering Committee - comprising members from various countries - to share insights on the evolving situation. Additionally, a direct independent communication channel has been established between the Technical Secretary, the Hellenic National Tsunami Warning Center (HL-NTWC) at the National Observatory of Athens (NOA), and Türkiye's Kandilli Observatory and Earthquake Research Institute (KOERI) to ensure the rapid exchange of urgent information, particularly during nighttime hours and weekends. A meeting is being organized by NEAMTWS Tsunami Service Providers to discuss operational procedures and communication strategies for Member States, especially in the event of non-seismic tsunamis. Additionally, a closed scientific meeting is under consideration, where experts will assess the current and evolving seismic situation around Santorini. Meanwhile, on Sunday, the Hellenic National Tsunami Warning Center (HL-NTWC) swiftly installed a new tide gauge station at Pori, on the northeastern coast of Santorini Island. This station will enhance sea-level monitoring in the area and play a crucial role in early warning efforts.