The land in Santorini continues to tremble. It has been doing it for days now, without respite. But yesterday, Wednesday 5 January, the strongest shock of this seismic sequence was recorded, with a magnitude greater than 5 (precisely 5.2), the first “moderate” intensity, which prompted the Greek authorities to declare the state of emergency . Even if at the moment there are no damage to things or people, the experts underline that in the area there had never been a seismic activity of this course by the initiative of the surveys, in 1964. And since the island was the scene Of a devastating earthquake of magnitude 7.7 just under 70 years, the attention with which the situation follows the Ellenic Civil Protection Ministry cannot be considered excessive.
We asked Carlo Doglioni, president of the National Institute of Geophysics and Volcanology, to tell us what is happening, the risks that are run and how the situation can evolve in the next few days.
Professor, what do we know about the causes of the current seismic sequence that is affecting the island of Santorini?
“A system of faults was activated in a north-east direction, south-west, immediately north-east of the island of Santorini. They are what we call extensional faults: in that area the Aegean sea is extending 2- 3 centimeters a year, and this involves the formation of those who are called Graben in literature, that is, structures that can produce seismicity “.
Is it therefore not a phenomenon linked to volcanic activity in the area?
“Greece is located above what is called a subduction plan: the Ionian and the part immediately north of Libya and Egypt go below Greece, Cyprus, Turkey. This subduction phenomenon generates seismicity e , at the same time volcanism. A release of fluids, the fusion of the rocks below and therefore the ascent of magma that produced the volcanoes ranging from the beloved to the Lazio volcanoes as Bracciano and Alban hills, and then Vesuvius, to get to the Aeolian islands, which are precisely A magmatic arch linked to the subduction under Italy.
The supervulcan that will brushed via Santorini (sooner or later)
“Estely fault is also somehow linked to these subduction phenomena, so we are talking about a geodynamic phenomenon that contemplates both seismicity and volcanism” explains Doglioni in Toray.it.
How do you expect the situation of these days to evolve?
“What has been seen in these days is an extremely energetic sequence: the number of events and their magnitude is growing, so the maximum peak has not been reached from which the descent begins, what we call the main shock, that is The most energetic event, from which in all the seismic sequences of the world, is then seen a reduction in the shocks and their power. more and more energy “.
The Greek authorities seem to take the situation very seriously.
“And they are good, even today there have been shocks with a magnitude greater than 5, therefore so -called moderate earthquakes, and it is impossible to exclude that in the next few days there are even more powerful ones. Each earthquake for us is in fact an experiment, because the Seismic history of the earth that we know with instrumental techniques is just 100 years old, practically nothing compared to the geological cycles that are thousands of years, and therefore we have a very limited forecasting capacity. It was an earthquake in the past in a given area, it can be repeated. These days it is also slightly south west compared to that of 1956, and therefore it affects the same fault but in a point where the crust has not yet broken, another detail objectively unrelavering “.
“In Santorini there was an earthquake of magnitude 7.7 in 1956, it cannot be excluded that there may still be a similar event”
The President of the Ingv Carlo Doglioni in Today.it
How much is the earthquakes of these days activate the underwater volcanoes of the area, like Kolumbo?
“The volcanoes respond to logic of evolution that are slightly different from those of the faults that generate earthquakes. A fault activates when there is an energy accumulated in the surrounding rocks that exceeds their elasticity limit, and there is a breakage of the Crust that releases this energy.
“What can happen is that there are faults that enter the magmatic chamber, and then in this case they produce a depressurization that causes the eruption. Or that the shaking caused by earthquakes affects the pressure in the magmatic chamber. In this sense, therefore, there can be an effect. 4-500 years, and therefore could still be there.