Magmatic Intrusion, Not Fault Slip, Drove Santorini-Amorgos Seismic Crisis

International researchers have definitively determined the source of the intense seismic unrest that characterized the Santorini-Amorgos region during the early months of 2025. A comprehensive study published in the journal Science confirms that the seismic crisis resulted from a massive, wave-like magmatic intrusion propagating through the Earth's crust, thereby ruling out tectonic fault slippage as the primary mechanism.

This significant subterranean event involved a body of molten rock spreading across an area exceeding 20 kilometers deep within the crust. The intrusion originated from an interconnected reservoir linking the Santorini volcano and the nearby Kolumbo underwater volcano. Scientists estimate the volume of magma involved was equivalent to nearly 200,000 standard Olympic-sized swimming pools. The seismic activity, which included hundreds of earthquakes with magnitudes reaching 4.5 or 5.0, prompted a local state of emergency, school closures, and considerable alarm among residents and tourists on Santorini.

The unrest, which spanned from late January through early March, initially raised concerns regarding a potential volcanic eruption or a major tectonic event, referencing the destructive magnitude 7.7 Amorgos earthquake recorded in the region in 1956. To map this movement with high accuracy, scientists utilized advanced machine learning techniques to analyze a dataset comprising over 25,000 recorded earthquakes. These tremors functioned as 'virtual deep stress meters,' enabling researchers to image the pressurized magma movement across both space and time.

The analysis revealed a complex, non-unidirectional process where the magma propagated in cascading pulses, repeatedly opening and closing subsurface fractures, which generated the observed high frequency of felt earthquakes. This dynamic 'pumping' behavior, involving cycles of dike opening and pressure fluctuation, was a crucial discovery that previous monitoring methods had not identified. Researchers from institutions including University College London (UCL) and the Aristotle University of Thessaloniki conducted the study.

Crucially, the research provided reassurance regarding immediate volcanic hazard, noting that the intruded magma lacked the necessary pressure or buoyancy to breach the surface and initiate an eruption. This finding establishes a foundation for more reliable, physics-based eruption forecasting. The methodology, which combines fundamental physics with artificial intelligence, is viewed as a significant advancement for monitoring volcanic activity in seismically active zones globally. Furthermore, prior research confirms that the magma systems of Santorini and Kolumbo are hydraulically connected, with the Kolumbo volcano harboring a growing magma chamber discovered in 2022, accumulating melt since its last surface eruption in 1650 C.E.