Santorini: Over 12,800 Earthquakes in 14 Days - What do the new data reveal?

Cyclades: Over 12,800 Earthquakes in 14 Days in the Santorini-Amorgos Zone - New Findings from NKUA

More than 12,800 earthquakes have been detected by the Seismology Laboratory (SL) of the National and Kapodistrian University of Athens (NKUA) in the Santorini-Amorgos zone from January 26 to February 8, 2025.

According to the latest announcement from NKUA, on Sunday, February 9, 2025, a total of 102 earthquakes were recorded, including 14 tremors with magnitudes greater than 4.0 on the Richter scale and 2 tremors exceeding 4.5. The largest earthquake occurred at 21:05:40 (Greece local time) with a magnitude of 5.0.

At the same time, NKUA has mapped the areas affected by landslides both near and far from the caldera.

Detailed Announcement from NKUA

From January 26 to February 8, 2025, the Seismology Laboratory of NKUA identified over 12,800 earthquakes in the Santorini-Amorgos zone using machine learning methods with strict quality control criteria. According to daily seismic data analysis (excluding machine learning methods), 102 earthquakes were recorded on February 9, including 14 with M≥4.0 and 2 with M≥4.5. The largest earthquake occurred at 21:05:40 (local time) with a magnitude of M=5.0.

Figure 1. Map of earthquake distribution in the Cyclades region (Santorini-Amorgos-Ios) recorded on February 8 (analysis using artificial intelligence) and February 9 (daily analysis). The radius of the circles corresponds to the magnitude of the earthquake (legend in the upper right corner), while the epicenters of earthquakes with magnitudes greater than or equal to 4.5 are marked with a star. The coloring represents the focal depth, according to the color scale (right).

Continuous Monitoring of Landslides During the Ongoing Seismic Sequence and Their Impact on Santorini's Natural and Built Environment

The research team from the Department of Geology and Geoenvironment at NKUA has been monitoring the associated phenomena on Santorini since the beginning of the seismic sequence. Researchers have collected data and made observations to map all landslide-affected areas and update their spatial distribution.

Landslides have occurred not only along the caldera slopes but also beyond them. Specifically:

• The southern coastal part of Santorini, outside the caldera

• The central-eastern section of the caldera slopes

• The northern part of the island

Landslide-Affected Areas

1. Southern coastal region (outside the caldera):

   • Slopes above Red Beach

   • Slopes above Vlychada Beach

2. Central-eastern caldera slopes:

   • Slopes above Athinios Port

   • Slopes 1.5 km north of Athinios Port (Akra Alonaki)

   • Slopes above the old port of Fira

   • Slopes below Imerovigli

   • Slopes in the Skaros area, Imerovigli

3. Northern part of the island:

   • Landslides along the Fira-Oia provincial road

A common feature of all affected areas is the presence of steep slopes, unstable volcanic materials, and older landslide deposits. However, the impacts vary from location to location.

At Red Beach, rockfall deposits have increased the accumulated material at the base of the slope above the beach. It is worth noting that the beach has been inaccessible for years due to previous rockfalls.

At Vlychada Beach, the impacts extend along a large portion of the shoreline. The movement and accumulation of unstable materials at the base of the nearly vertical cliffs have significantly reduced the beach's width. However, due to wave action and the area's lithology, the beach is expected to gradually return to its previous state as geological materials redistribute along the coast.

At Athinios Port, landslides have been limited in scale. The port facilities, passenger waiting areas, dining establishments, shops, and parking lots in the coastal zone have remained unaffected.

North of Athinios Port, landslides have occurred on slopes far from built structures such as houses, infrastructure, and networks. Some unstable materials have fallen into the sea.

Further north, above the old port of Fira, in Imerovigli, and Skaros, landslides have occurred on slopes below inhabited areas (Fira, Imerovigli) located at the caldera rim. Similar to Athinios, no impacts on built environments have been recorded.

In the northern part of the island, along the road connecting Oia to Fira, rockfalls have made vehicle passage hazardous.

Protection Measures and Future Actions

This assessment highlights the landslide-affected areas in Santorini, where Civil Protection authorities have implemented temporary non-structural measures. These include restricting access to high-risk areas for residents and visitors and prohibiting vehicle circulation on sections of the road network near landslide-prone zones.

These locations should be prioritized for further study after the seismic sequence concludes. Effective structural measures tailored to Santorini’s volcanic landscape and unique natural beauty should then be implemented.