Q&A: Things you need to know about the earthquake near Santorini

From January 24th, weak to moderate earthquake accumulation has been recorded around Santorini, Greece. Seismic activity is concentrated in the area between the islands of Santorini and Amorgos, with the center approximately 25 km northeast of Santorini.

The Geomar Helmholtz Center for Ocean Research Kiel and the GFZ Helmholtz Center for Geosciences Potsdam categorize the current events of these questions and answers.

What causes many earthquakes near Santorini, a volcanic island?

Many earthquakes, 4-10km deep, have occurred over 10 days between Santorini, the underwater volcano Korumbo and Amorgos. Quakes has reached an unprecedented size of 5 or more. This activity begins with a weak tremor under Santorini and travels northeast along the crustal zone of weakness running from southwest to northeast.

Such earthquake swarms are not uncommon in active volcanic systems and are also repeatedly observed under Santorini and Korumbo (Bohnhoff et al. 2006). One possible cause is volcanic activity, namely molten rocks or other liquids rising upwards in the Earth’s crust. Another possibility is the movement of the Earth’s plates, which can lead to rock stress and sudden release of these stresses, and thus earthquakes.

Combinations are also possible. Individual segments of the Aegean tectonic plates around Santorini travel apart from each other a few millimeters away. This leads to the stretch and thinning of the Earth’s crust, just like pulling apart the durable fabric, which becomes thinner in the center. Where the crust extends, liquids, and magma can rise.

Can you predict these earthquakes?

It is not possible to predict when a swarm of such earthquakes will occur. There is a precursor phenomenon, especially in volcanic earthquake groups. We are currently investigating the temporal development of earthquake swarms, such as uplifts and subsidence, and the changes that occur therewith.

Can you predict a volcanic eruption?

Volcanic eruptions are also not predictable. However, unlike earthquakes, volcanic eruptions often have distinct precursor phenomena. These include ground earthquakes and herd earthquakes that intensify before the eruption and move towards the Earth’s surface or the seabed. So far, there is not enough data to warn of an imminent eruption. Nonetheless, warnings to avoid cliffs, for example, are correct and important.

What happens if a major earthquake occurs in 1956, such as an eruption or a major earthquake?

In July 1956, two earthquakes, over seven, occurred in areas with current earthquake-active earthquakes. One of them originated in the crust on Earth, causing a local tsunami with wave heights of up to 22 meters on Amorgos Island. The earthquake caused major damage in the area. Fifty people have died. The current earthquake series shows much weaker earthquakes. The 1956 rupture zone has not yet accumulated enough energy again due to its low displacement velocity, but it cannot rule out movements of other previously inert rupture zones.

If an earthquake or volcanic eruption that rivaled the 1956 earthquake (the last major eruption of Korumbo volcano in 1650) occurs today, it is likely that strong effects could be expected due to the dense population. there is. Strong ground shaking can cause collapse of buildings, particularly old or not built to withstand earthquakes. The tsunami can hit coastal areas and lead to flooding not only on Santorini, but also on nearby islands and mainland Greece. Caldera submarine landslides could also occur. However, the probability of this is still low.

Is the Santorini volcanic eruption imminent?

The area directly below the Santorini volcano is currently seismically mild. Finally there was a similar seismic activity, with a very shallow earthquake in 2011 at a depth of 1-2 kilometres. However, there were no eruptions.

What is the risk of a tsunami there?

The Mediterranean has more tsunamis than other parts of the world. Approximately 80% of tsunamis are caused by powerful earthquakes that move up and down the seabed. This can occur in the Mediterranean as well as in the Mediterranean.

Volcanic eruptions in areas such as Santorini volcano can also cause tsunamis due to underwater explosions and landslides.

Volcanic processes can also cause landslides on land and underwater. This can replace large amounts of water and cause a tsunami. Greek authorities and international researchers are monitoring the situation very closely. The possibility of a tsunami or a major earthquake cannot be ruled out.

How can you monitor such vulnerable regions?

Modern monitoring systems make seismic activity and volcanic processes easy to observe. Greece Earthquake Services operates a close surveillance network in areas that also record small earthquakes. Geomar, GFZ and other partners have launched a rapid response mission as part of the MultiMarex project. With our Greek partners (Institute of Physics and Geography, University of Athens), we have installed additional instruments at the seabed and at the Santorini Caldera and are on-site to monitor seismic activity.

The purpose of monitoring is to accurately record and quantify the number, location and intensity of earthquakes. Over the next few days, we will be able to recognize whether the recently observed increase in seismic sequence magnitude and intensity continues or subsides.

What measures are needed to protect the population?

As long as seismic activity continues, the risk of landslides is high, especially in steep coastal areas. Therefore, people should avoid beaches and cliffs. Earthquakes that are more important than ever recorded can also cause tsunamis. Currently there are no measurements indicating earthquakes of this size.

Greek authorities send warnings via cell broadcasts in several languages ​​to protect rules of conduct and protection measures directly on mobile devices. To do this, you must activate receipt of emergency notifications.