Deep Seismic Tremors in the 2025 Santorini Seismo‐Volcanic Crisis Highlight Magmatic Feeding from a Mid‐Crustal Reservoir

The intense seismic swarm that took place in the Santorini‐Amorgos region in early 2025 was felt by local inhabitants and caused the declaration of a state of emergency at Santorini Island. At the same time, an intense debate emerged within the scientific community in early 2025 about whether this seismic crisis was tectonic or volcanic in origin.


Using advanced seismological tools that enable effective detection and location of seismic signals, we have created detailed catalogs not only of the earthquakes comprising the seismic swarm, but also of the continuous signals called seismic tremors that occurred simultaneously with the swarm.

The spatio‐temporal characteristics of these two catalogs confirmed the volcanic origin of the 2025 Santorini crisis, with the possible involvement of deep magmatic fluids near a mid‐crustal magma reservoir located a few kilometers southeast of Kolumbo volcano.


Two families of seismic tremor detected during the crisis: deep tremor (white text), and tremor related to the earthquake swarm (blue text).
Location of sources from the two tremor families: deep tremor (green dots) located in the vicinity of a mid-crustal melt reservoir (orange, from Autumn et al., 2025), and tremor (light blue dots) collocated with the earthquake swarm (dark blue dots).


The full study is published in: AGU journal


References :

Autumn, K. R., Hooft, E. E. & Toomey, D. R. Exploring mid-to-lower crustal magma plumbing of Santorini and Kolumbo volcanoes using PmP tomography. Geochem. Geophys. Geosyst. 26, e2025GC012170 (2025).

Isken, M. P., Karstens, J., Nomikou, P., Parks, M. M., Drouin, V., Rivalta, E. et al. Volcanic crisis reveals coupled magma system at Santorini and Kolumbo. Nature 645, 939–945 (2025).

Lomax, A., Anagnostou, V., Karakostas, V., Hicks, S. P. & Papadimitriou, E. The 2025 Santorini unrest unveiled: Rebounding magmatic dike intrusion with triggered seismicity. Science 390, eadz8538 (2025).

Scientific contacts:

  • Jean Soubestre – ISTerre, Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, Univ. Gustave Eiffel, Grenoble, France
  • Nikolai Shapiro – ISTerre, Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, Univ. Gustave Eiffel, Grenoble, France
  • Florent Brenguier – ISTerre, Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, Univ. Gustave Eiffel, Grenoble, France