The Dodecanese Islands region in southeastern Greece lies within one of the most seismically active zones in the Mediterranean, driven by the convergence of the African and Eurasian tectonic plates along the Hellenic Arc. This subduction zone produces frequent shallow to intermediate-depth earthquakes, with the broader Aegean extensional regime contributing to normal and strike-slip faulting. Historical records document destructive events in the area, including the 1926 magnitude 7.1 quake near Rhodes and multiple sequences in the 20th century linked to the same plate-boundary dynamics.
Between 20:19 on 27 January 2025 and 22:22 on 26 February 2025, a significant earthquake swarm (S20250128.1) was recorded in the Dodecanese Islands. Over 722 hours and 3 minutes, 2,819 events were detected. This swarm represents the second such episode since 2000, following the previous swarm in 2009. Swarms of this nature typically lack a dominant mainshock and instead feature clustered activity that migrates along fault systems, often triggered by fluid migration or stress transfer in the crust.
Analysis of the first 100 events reveals predominantly low-magnitude seismicity, with values ranging from 2.0 to 3.1. The largest events reached 3.1 on 30 and 31 January 2025. Depths were consistently shallow, mostly between 3 and 18 km, with the majority clustered around 5–13 km. Early activity on 27 January showed events at depths of 5–18 km and magnitudes up to 2.8, while later events in the sequence maintained similar depth ranges but included slightly higher magnitudes around 3.0. This pattern indicates brittle failure in the upper crust, consistent with the extensional tectonics of the Aegean.
Such characteristics align with regional geology, where the Dodecanese sit near the transition from the Hellenic subduction zone to the Anatolian plate boundary. The absence of deeper events in the initial phase suggests the swarm remained confined to the seismogenic layer above approximately 20 km. No events exceeded magnitude 3.1 in the examined subset, underscoring the swarm’s diffuse energy release rather than a classic foreshock-mainshock sequence.
This episode adds to the long-term seismic catalog of the eastern Mediterranean, where monitoring networks have improved detection of low-magnitude activity since the early 2000s. Continued observation of swarm evolution can refine understanding of stress accumulation along local faults.