The Greek island of Santorini has been placed in a state of emergency after experiencing its strongest earthquake following days of continuous tremors.
A magnitude 5.2 quake struck Santorini on Wednesday evening, the first to surpass 5.0 since tremors began last week. On Thursday, two larger tremors jolted the island, each exceeding a magnitude of 4.0.
Santorini’s last major earthquake, a magnitude 7.5 tremor in 1956, killed at least 53 people.
Here is what we know so far:
What is happening in Santorini?
The island, one of Greece’s Cyclades islands in the Aegean Sea, has been experiencing near-constant tremors since January 27, 2025, with thousands of earthquakes recorded so far.
The most powerful earthquake recorded since then – occurring on Wednesday evening – registered a magnitude of 5.2 on the Richter scale.
Magnitude measures the size of an earthquake with increments represented by decimal points. An earthquake of magnitude 6.0 or higher is classified as severe, while a magnitude of 5.2 is considered moderate.
Santorini is situated along the Hellenic Volcanic Arc, which extends from the Peloponnese in southern Greece through the Cyclades islands. The region is also home to two volcanoes: Nea Kameni, a small islet within Santorini’s caldera, and Kolumbo, an underwater volcano located approximately eight kilometres (five miles) northeast of the island.
The Santorini-Amorgos earthquake swarm just keeps going. It has now produced over 1,000 individual events since it began on January 27. pic.twitter.com/KQwxEj0Vbb
— Nahel Belgherze (@WxNB_) February 5, 2025
Where are the epicentres of the earthquakes affecting Santorini?
The earthquake epicentres are concentrated in a growing cluster between Santorini, Anafi, Amorgos and Ios islands. Seismic activity remains concentrated between Santorini and the nearby island of Amorgos.
The epicentres are located beneath the seabed, which is good news; according to scientists, land-based earthquakes generally cause greater destruction. Greece lies in a highly seismically active part of the world, and earthquakes are not rare.
What are the main concerns?
Authorities are making preparations in case of an even larger quake as the tremors do not yet show any sign of easing. On Wednesday, authorities warned of landslide risks to parts of the island.
“We are not yet in a position to say that we are seeing any evidence that would lead to the sequence slowly coming to a conclusion,” Vassilis K Karastathis, a seismologist and director of research at the National Observatory of Athens, told reporters.
“We are still in the middle of the road, we haven’t seen any easing, any sign that it’s heading towards a regression.”
The quakes have not caused injuries or major damage. According to reports, more than 11,000 people have departed from Santorini as a result of the tremors. According to the 2021 census, Santorini, which is popular with tourists, has a permanent population of 15,000.
Could the earthquakes cause a volcanic eruption?
Although Santorini is in close proximity to two volcanoes, experts consider an eruption unlikely. Scientists emphasise that the current earthquakes are unrelated to volcanic activity and do not pose a specific volcanic hazard.
Last week, Greece’s Ministry of Climate Crisis and Civil Protection reported that sensors detected “mild seismic-volcanic activity” within Santorini’s caldera. A similar event in 2011 persisted for 14 months without causing any volcanic issues, however.
“At this moment, I don’t think there is any hazard from the submarine volcano of Kolumbo and the volcanic complex … however, I should say that we cannot exclude the arrival of a second pulse of magma, and [if so] this episode will repeat,” Athanassios Ganas, research director of the National Observatory of Athens, told Al Jazeera.
The island does have a long history of volcanic activity, however. At about 1,600 BC, one of the most massive volcanic eruptions in human history shaped Santorini into its present geological form.
Between 2011 and 2012, the island underwent significant seismic activity due to magma movement beneath the surface.
Will the tremors continue for a long time or get worse?
“We cannot exclude the possibility to have an earthquake of around 6.0 on one of the neighbouring faults,” Ganas told Al Jazeera.
“Because all these seismicity transfer stresses to neighbouring faults that are long enough, about 15 kilometres, and this fact means that they have the potential for a magnitude 6.0 earthquake,” he added.
However, Ganas emphasised this is not the most likely scenario. “This is the second one in priority. The first scenario is that we are in the middle of a seismic swarm,” he said.
A seismic swarm is a series of many small to moderate earthquakes occurring in a localised area over a short period, ranging from hours to months, without a single, dominant mainshock.
How are Greek authorities responding?
Greek Prime Minister Kyriakos Mitsotakis is expected to visit Santorini on Friday.
Local authorities have shut schools until Friday in Santorini and Amorgos, dispatched rescuers and advised residents to avoid ports and indoor gatherings.
The government said the state of emergency would remain in place until March 3, to allow it to respond to the population’s needs and the consequences of the seismic activity.
