1,1,2,- 1National and Kapodistrian University of Athens, Department of Geology and Geoenvironment, Section of Geophysics and Geothermy, Athens, Greece (kpavlou@geol.uoa.gr)
- 2University of Patras, Patra, Greece
- 3Institute of Physics of Earth’s Interior and Geohazards, UNESCO Chair on Solid Earth Physics and Geohazards Risk Reduction, Hellenic Mediterranean University Research & Innovation Center, 73133 Chania, Greece
Since January 27, 2025, intense seismic activity has been recorded in the offshore area between Santorini and Amorgos, with more than 4,500 events. The sequence began inside the Santorini caldera and gradually migrated northeast. The strongest earthquake was an ML 5.3 event on February 10, 2025. In this study offers a seismological analysis that integrates patterns of seismic activity over space and time, static Coulomb failure stress changes, and shifts in seismic velocity structure to explore the mechanisms behind the swarm's development.
The analysis is based on seismological data from the NKUA monitoring network for the period from 1 January to 3 March 2025. Coulomb stress changes were computed for events with Mw ≥ 4.7 using elastic half-space modelling, while a modified Wadati method was applied to a subset of well-located events to estimate the regional average Vp/Vs ratio. The results reveal a northeastward migration of seismicity, closely aligned with NE–SW-oriented fault structures in the Santorini–Amorgos area.
Coulomb stress modelling for the events of magnitude Mw > 4.8 reveals predominantly positive stress changes at the hypocenters of subsequent earthquakes, suggesting that static stress transfer contributed significantly to the progressive activation of neighboring faults. At the same time, the estimated Vp/Vs ratio of approximately 1.75 is consistent with a fluid-influenced seismogenic environment, supporting the involvement of crustal heterogeneities and possible fluid-related processes during the swarm.
The combined observations suggest that the 2025 Santorini–Amorgos seismic sequence was controlled by the interaction between fault-driven stress redistribution and variations in crustal properties. This approach provides new insights into earthquake triggering mechanisms in complex volcanic–tectonic settings of the South Aegean and highlights the importance of multidisciplinary analyses for seismic hazard assessment.
How to cite: Pavlou, K., Sardeli, E., Karakonstantis, A., Pappas, S., Athanasopoulos, A., Tomaras, A., Kazakou, A.-A., Travlostathi, C., and Vallianatos, F.: Spatiotemporal distribution, Coulomb stress changes, and temporal variations in Vp/Vs ratio during the 2025 Santorini-Amorgos seismic swarm., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10805, https://doi.org/10.5194/egusphere-egu26-10805, 2026.
