What trembles Santorini? The AI ​​reveals a massive magma movement under the Aegean Sea

Analysis of the earthquake swarm around Santorini reveals the origin and development of the seismic crisis.

At the beginning of 2025, the Greek island of Santorini and its surroundings were shaken by tens of thousands of earthquakes. A new study in Nature From GFZ Helmholtz Center for Geosciences and Geomar Helmholtz Center for Ocean Research Kiel, directed with international partners, now offers the first detailed geological explanation of this seismic crisis.

By combining measures from terrestrial earthquake stations with data collected by instruments on the seabed near the underwater volcano of Kolumbo (about 7 km from Santorini), the researchers applied an advanced AI technique to identify the earthquake activity. Their analysis shows that nearly 300 million cubic meters of magma have passed deep in the crust and blocked about four kilometers under the bottom of the ocean. While traveling upwards, the magma fractured the surrounding rock, producing thousands of earthquakes and tremors.

A seismically unstable region – Geological context

Santorini is found in the eastern Mediterranean in the Hellenic volcanic arc, one of the most geologically active areas in the region. The island group forms the edge of a caldera created by a colossal eruption about 3,600 years ago, a historic event in volcanic history.

The Kolumbo’s active submarine volcano is in the immediate vicinity. In addition, the region is crossed by several active geological fault zones, which is the result of the African plate pushing the northeast against the Hellenic plate. The terrestrial crust under the Mediterranean region was divided into several microplacas which move against each other, and in certain cases, under -ductors and found, obtain volcanic activity.

Santorini produced multiple eruptions was a historic period, more recently in 1950. In 1956, two serious earthquake series occurred in the Aegean of the South, just 13 minutes apart, between Santorini and the neighboring island of Amorgos. They had amplitudes of 7.4 and 7.2 respectively, triggering a tsunami.

The earthquake swarm that initiated at the end of January 2025 in the late January 2025 in this region. During the crisis, more than 28,000 earthquakes were recorded. The strongest of them have reached amplitudes over 5.0. The serious tremors caused a great public concern during the seismic crisis, in part because the cause was initially clear, being potentially tectonic or volcanic.

What happened underground? – Results of this study

The new study now shows that the earthquake swarm has been triggered by the deep transport of magma. The chain of events had already started in July 2024, when the magma became a shallow reservoir under Santorini. This initially led to a barely noticeable uprising of Santorini of a few centimeters. At the beginning of January 2025, the seismic activity intensified and, from the end of January, the magma began to rise from the depths, accompanied by an intense seismic activity.

However, seismic activity has moved away from Santorini over a distance of more than 10 kilometers to the northeast. During this phase, the foci of earthquakes moved to several depths of 18 kilometers higher at a depth of only 3 kilometers under the seabed. The high-resolution temporal and spatial analysis of the distribution of earthquakes, combined with radio-satellite interferometry (ISAR), GPS Floor stations and seabed resorts have made it possible to model events.

Dr. Marius Isken, geophysicist of the GFZ and one of the two main authors of the study, says: “Seismic activity was typical of the rise of magma through the crust precision. “”

Following the Magma movement, the island of Santorini was still soothed, which the authors interpret as proof of a hydraulic connection previously unknown between the two volcanoes. Dr. Jens Karstens, marine geophysicist at Geomar and also author of the study, explains: “Thanks to close international cooperation and the combination of various geophysical methods, we were able to follow the development of the seismic crisis in almost real time and even by learning something on the interaction between the two volcanoes.

See many angles – Methods

Two factors in particular allowed exceptionally detailed mapping of the basement. On the one hand, an AI managed method has developed at the GFZ level for the automatic assessment of large sets of seismic data. Secondly, Geomar had already deployed underwater sensors in the Crater of the Kolumbo underwater volcano in early January as part of the Multi-Marex project. These sensors not only measured the seismic signals directly above the tank, but also the pressure changes resulting from the sagging of the seabed up to 30 centimeters during the intrusion of the magma under Kolumbo.

The scientific research activity on Santorini continues despite the drop in seismic activity. GFZ performs repeated gas and temperature measurements on Santorini, while Geomar is currently eight platforms of seabed sensor in operation.

Professor Heidrun Kopp, professor of marine geodesy at Geomar and Multi-Marex project manager, said: “The joint results have always been shared with the Greek authorities in order to allow the fastest and most precise evaluation of the possible situation in the event of new earthquakes.” The co-author of Professor Dr Paraskevi Nomikou is a professor of geological oceanography at the University of Athens and works in close collaboration with the Institutes of German partner on the Multi-Marex project. It adds: “This long -standing cooperation has made it possible to jointly manage events at the beginning of the year and to analyze them with so precisely from a scientific point of view. Understanding the dynamics in this geologically very active region as precisely as possible is crucial for the security and protection of the population.”

Reference: “The volcanic crisis reveals a magma system coupled with Santorini and Kolumbo” September 24, 2025, Nature.
Two: 10.1038 / S41586-025-09525-7

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