We live in a strongly seismic country, where, unfortunately, earthquakes are only spoken of after violent events, to count the damage and the number of victims.
Sabrina Mugnos in her recent "Terra inquieta" (Hoepli editore, 2022, pp. 118, also e-book) takes us on a journey through Italy to understand how and why earthquakes occur, which in fact are a manifestation of life of the planet that cools down.
The author also explains how the risks are not linked only to the extent of the possible earthquake, but also to the building density and the urban organization of a given territory, which define its vulnerability.
The clear description of the seismic phenomena, from the causes to the methods of measurement and prevention, is accompanied by a handbook of the few behavioral rules to be followed in ongoing events.
However, we ask Sabrina Mugnos first of all if something is changing in Italy from a geological point of view given that in recent years there have been several significant seismic events:
“Italy is a strongly seismic country as it is compressed in the convergence of two large plates: the African and the Eurasian one. Their motion creates enormous mechanical tensions that build up until they are released abruptly in the form of earthquakes of varying intensity. Geological movements are very slow and span periods of millions of years; therefore, this geological configuration will not change for the many generations that will alternate in these lands after ours.
As an example, the number of earthquakes located in Italy in 2021 is slightly lower than in 2020 and has remained stable since 2019. Numbers lower than those recorded in the years 2016-2017-2018 which, however, were characterized by the seismic sequence in Central Italy. Furthermore, it should not be overlooked that over the last ten years the National Seismic Network has progressively improved not only in the number and quality of the tools used but also in the systems for automatic recognition and revision of seismic events ".
Which areas are most at risk from dangerous earthquakes?
“The areas at greatest risk are the Apennines (especially central-southern) and the Eastern Alps”.
Does living in areas with low seismic risk mean being able to sleep peacefully?
“The seismic risk in our country is a condition that should never be neglected as it is a compendium of various parameters that characterize a territory. The first is the danger, that is the probability that, in a certain place, a certain shaking of the ground of a certain intensity occurs. So we have vulnerability, understood as the propensity of a structure to suffer damage of a certain level, in the face of a seismic event of a given intensity. Finally, exposure, which is a measure of the importance of the object exposed to the risk in relation to the main characteristics of the built environment. In other words, if it is true that the intrinsic danger of the place (i.e. how they move under the plates) is the starting point, the type of buildings that there are, on which land, with what urban planning and the degree of population also count. ".
How is the seismic situation in Sardinia?
“Sardinia is a geologically stable island, that is, without active tectonics. The sporadic earthquakes that occur generally occur along ancient coastal faults and have often been related or confused with other natural phenomena such as landslides, thunder and lightning. It must also be said that the nature of its rocky base, made of compact metamorphic rocks, means that seismic events are perceived throughout the region. Historically, the two strongest earthquakes in Sardinia are that of 4 June 1616, which affected all of southern Sardinia and is remembered by an engraving contained in the Sacristy of the Cathedral of Cagliari, and that which occurred, still in the southern part of the island, on 17 August 1771. In more recent times we remember the earthquake that occurred in the north of Sardinia, in Gallura, on 13 November 1948. For this event there is more documentation collected by the newspapers of the time ".
What is the situation of the Italian volcanoes? Is there anyone that worries more than others?
“For now, everyone does their own 'job': in perennial activity Etna and Stromboli and the Neapolitan ones that are also the most dangerous 'asleep'. However, we have excellent monitoring systems that keep them under continuous control ”.