[OC] Sharp Increase in M≥4 Earthquakes in the Aegean Region in 2025 (USGS Data)

This visualization shows the annual number of earthquakes with magnitude ≥4.0 in the broader Aegean Plate region and western Anatolia.

In 2025, the region has already recorded more than 500 M≥4 events, compared to a long-term average of roughly 200–250 events per year. This represents more than a twofold increase relative to typical activity levels.

Context:

The Aegean region is part of the Aegean–Anatolian deformation zone, where the Aegean microplate interacts with the Anatolian and African plates. It is also home to the South Aegean volcanic arc, including systems such as: Santorini, Kolumbo, Nisyros, Methana, Milos.

A significant portion of the 2025 seismicity has been concentrated around Santorini, where more than 350 earthquakes M≥4 were recorded in 2025 alone. Geodetic measurements and recent studies suggest that part of this swarm is associated with subsurface magma movement rather than purely tectonic fault slip.
Importantly, Santorini is capable of very large explosive eruptions. Its Late Bronze Age (Minoan) eruption reached VEI 7 and produced tens of cubic kilometers of material, forming the present-day caldera.

Approximately 7 km northeast of Santorini lies Kolumbo, a submarine volcano that last erupted in 1650 in a highly explosive submarine event. Recent marine surveys have documented elevated seafloor temperatures, new hydrothermal vents, gas emissions (CO₂, SO₂, H₂S), and seismic signals consistent with magma recharge at 2–4 km depth beneath the seafloor.
Geological evidence indicates that it also has the capacity for powerful explosive eruptions, particularly due to magma–seawater interaction in a shallow marine setting.

This post focuses strictly on earthquake frequency trends based on USGS catalog data (M≥4.0 threshold). Interpretation of volcanic processes is based on published geophysical studies and monitoring reports.

Data source: USGS Earthquake Catalog
Region: Aegean Plate
Magnitude threshold: M ≥ 4.0
Visualization: Python