Santorini's 2025 Seismic and Volcanic Crisis: A Rare Event with Complex Insights
The Greek scientific community presented groundbreaking findings on the Santorini-Amorgos seismo-volcanic crisis during a recent event at the National Observatory of Athens, attended by Climate Crisis and Civil Protection Minister Giannis Kefalogiannis. The event, titled 'The Seismo-Volcanic Crisis of Santorini: One Year After – Results and Conclusions', shed light on the conclusions of Greece's permanent scientific committees on seismic risk and the monitoring of the Hellenic Volcanic Arc.
Vassilis Karastathis, director of the Athens Geodynamic Institute, described the 2025 activity as an earthquake swarm, emphasizing its rarity due to the high number of earthquakes and the short time frame. He noted that the majority of events had a tectonic origin, but a significant portion indicated the intrusion of magmatic fluids, creating a 'tectono-magmatic' sequence. Between January 26 and June 30, 2025, scientists recorded over 21,000 earthquakes, with the monitoring network logging an astonishing 19,523 in the first quarter alone. The island experienced a staggering 216 earthquakes above magnitude 4 between February 2 and 12, far surpassing comparable national figures from 2023 and 2024.
Experts linked the crisis to a period of volcanic unrest between August 2024 and January 2025, although they described that earlier phase as significantly weaker than the 2011-2012 episode. Karastathis highlighted the enormous workload the crisis produced, as earthquakes occurred at an exceptionally high frequency, causing automated epicentre systems to struggle with overlapping signals. This led to stricter criteria and enhanced manual checks, with the institute completing its analysis in the summer of 2025 and presenting the results at a global conference in Lisbon.
The final processing produced updated epicentre maps using new seismic velocity models and data from a distributed acoustic sensing (DAS) system. The analysis placed the seismicity at depths of 5 to 15 kilometres and found no evidence of magma rising close to the surface. Scientists linked the epicentres to known tectonic structures and suggested that the shifting pattern indicated magmatic fluids penetrating existing faults. Karastathis revealed that 70 to 76 per cent of the earthquake mechanisms were tectonic, while the remainder showed magmatic characteristics. Importantly, no seismic signals or background 'noise' associated with an imminent eruption or the formation of a new volcano were detected.
Efthymis Lekkas, president of the Earthquake Planning and Protection Organisation (OASP), praised the real-time crisis response, describing it as a complex event with global uniqueness. He stressed the importance of managing landslide risks inside the caldera. Kostas Papazachos, a seismology professor and president of IMBIS, emphasized the long-term monitoring of the volcano, stating that scientific observation actively supports decision-making during crises. The authorities have strengthened monitoring infrastructure with permanent stations on Santorini, Thirasia, and Nea Kameni.
Vassilis Sakkas, an assistant professor, presented geodetic measurements showing intense ground deformation in the caldera, including uplift of up to 60 millimetres and horizontal displacement of 70 millimetres. During January and February 2025, scientists observed seismicity migrating towards the Anydros area at a speed of 4 to 5 kilometres per day, while Imerovigli recorded subsidence of up to 80 centimetres per year. Sakkas noted a reduction in deformation rates from March 2025, although Santorini continued to show uplift. He advocated for continuous geodetic, seismological, and geophysical monitoring to enhance early understanding and forecasting.
Dr Sp. Vasilakos, director and board president of the National Observatory of Athens, concluded the event by stating that the meeting marked a new era for the Observatory and the Geodynamic Institute. The dialogue aimed to strengthen public services and improve Greece's preparedness for future crises, leaving a lasting impact on the scientific community and the public alike.
