The 2025 South Aegean Sea Seismic Swarm Activity in Natural Time and the Generalized Gutenberg–Richter Law

A strong seismic swarm occurred in the south Aegean Sea from late January to March 2025. Here, we apply natural time analysis (NTA), which can identify the critical stage before strong earthquakes, and find that all earthquakes of magnitude five or larger have been preceded by criticality. Moreover, we study the frequency–magnitude distribution of the seismic swarm and suggest a generalization of the Gutenberg–Richter law, which is compatible with Tsallis nonextensive statistical mechanics. This suggestion is tested for different earthquake catalogs available for this seismic swarm with successful results. Since NTA has already been applied to the strongest seismic swarm ever recorded in Japan, observed in 2000 in the Izu Islands region, we apply the present suggestions to the case of another swarm observed during June 1980, which was the strongest seismic swarm in the same region since 1979. The strongest magnitude class M7 earthquake of that swarm was also preceded by criticality in the NTA. Finally, we show that earthquake nowcasting could be applied to predict in advance that no earthquake exceeding magnitude 6.5 would occur during the south Aegean seismic swarm.