Locals and tourists deserted Santorini early in 2025 due to the seismic swarm. Credit: AMNA/Orestis Panagiotou
An international research team, including Greek scientists, has unveiled the hidden processes that drove the intense seismic activity near Santorini, Greece, in early 2025.
Their study, published in the journal Science, definitively attributes the activity to a massive magmatic intrusion—a vertical layer of magma—that propagated in waves more than 20 kilometers (12 miles) across the Earth’s crust at depths exceeding 10 kilometers (6 miles) beneath the seafloor.
The scale of the magma intrusion under Santorini
The researchers emphasized the sheer volume of magma involved, noting it was enough to fill nearly 200,000 Olympic-sized swimming pools.
This significant event generated a level of seismic activity that was unique globally for the number of earthquakes concentrated within such a short period.
The 2025 event included hundreds of perceptible earthquakes, some exceeding magnitude 5.0, which triggered a local state of emergency, school closures, and widespread alarm among residents and visitors.
Related: Magma Shift Between Santorini and Kolumbo Volcanoes Fueled 2025 Earthquakes, Scientists Say
Santorini earthquakes were not due to a tectonic fault slip
A critical uncertainty dominated the crisis: was the shaking due to volcanic activity, signaling a potential impending eruption? Or, a tectonic fault slip, possibly as a foreshock to a larger, destructive earthquake, like the magnitude 7.7 quake that struck the same region in 1956?
The new research now provides a clear answer, ruling out tectonic fault slip as the primary cause.
The research team used high-resolution imaging that clearly identified and mapped the intrusion of a magmatic dike (a sheet of magma), which ultimately triggered the seismic activity.
The detailed spatiotemporal imaging revealed that the magmatic intrusion was not a simple, unidirectional process. Instead, the team made a crucial discovery: the intrusion advanced in waves.
It manifested in pulses, opening new cracks, closing others, and pushing the magma forward intermittently. This wave-like magma intrusion and the resulting pulsed pressure changes impacted the stress field, leading to the generation of the rapid, “cascading” rate of earthquakes.
Related: Santorini Earthquakes are Entirely Volcanic, Expert Says
