No, it is not written anywhere that the Messina bridge collapses with an earthquake 6.9. Indeed, the Corriere della Sera who published the news changed the title of the article (which remained viewable online). But then “Standing in the event of an earthquake?”. Certainly, even after the approval of the “final project” of the bridge over the Strait of Messina by the Cipess, doubts and criticisms do not collapse. Many say about it on the mega work that has the Minister of Infrastructure as the main sponsor, Matteo Salvini, and the earthquakes are among the most discussed themes. But on parameters and reference limits there is a lot of confusion.
“The bridge that resists a 6.9 earthquake”
Total length of 3,666 meters, of which 3,300 meters suspended on the Strait of Messina. It will be the suspended bridge with the longest unique span in the world. The cost is 13.5 billion euros to which are added 1.1 billion for other connected railway works. 248 percent more than the original project.
So much has been said of the resistance of the bridge to earthquakes and there is a lot of confusion on the topic. For example, a recent article very shared and commented on the Corriere della Sera headlines “The longest single span bridge in the world: 3.3 kilometers (and which resists a 6.9 earthquake earthquake)”. Then the title was modified. But let’s go to degrees.
From a seismic point of view, the Strait of Messina is among the most active areas of the Mediterranean: in fact it is located between the Eurasian plate and the African microplacca, with systems of active faults that cross the area.
In 1908 a destructive earthquake of magnitude 7.1 Richter and the tsumer arose resulted in 100,000 deaths. In addition to the characteristics of the area, the doubts of critics arise from a study entitled “The Messina Strait: Seismottecttonic and the source of the 1908 Earthquake”, published in the international magazine Earth-Science Reviews. In the study, The authors reconstruct the structure from which the destructive earthquake of Messina from 1908 would have arisen. From the sea, about 3 kilometers from Sicily, the fault “enters” the Calabrian side.
A problem is then raised: from their calculations the maximum developable magnitude is 6.9, less than 7.1 recorded in 1908. But, at the same time, the value is doubtful: it is not very appropriate compared to other studies and to the damage seen in the Messina earthquake. The value 6.9, never used in the design of the bridge, suggests that the area needs new insights since the estimates are uncertain. The fault could therefore generate even more powerful earthquakes than 6.9, but also of 7.1.
What does the “definitive” project of the bridge says: how much he resists earthquakes
According to the definitive project of the bridge over the Strait, the seismogenetic potential of the area is 7.1, the same magnitude recorded in the 1908 earthquake. Consequently, the design of the work is centered on this assumption: the bridge must be able to resist an earthquake comparable to the maximum never recorded in the area, that is, at 7.1 of 1908.
The designers of the bridge considered the “extremely rare” 1908 event and with return times of over two thousand years. Even more rare are considered earthquakes that reach up to 7.4. Designing and building the structure by adapting it to the maximum risk desirable for the area would make it safe from natural disasters.
About 400 geological, geotechnical and seismic investigations were carried out, with over 300 elaborate. The current project was presented 15 years ago, with some updates presented in its latest version of 2023. In addition to 7.1, the other value to consider is the PGA, in English “Peak Ground Acceleration”, and indicates how much the ground is shaking during an earthquake. We can say that “brutality” measures.
Inquiry: the document that demolishes Matteo Salvini’s project
It is a fundamental index used in the design of the buildings and for the bridge it was set at 0.58 g, which corresponds to that 7.1 recorded in 1908. This is how the buildings would be able to “oscillate” even if subjected to this force and without collapsing. But the final project is far from definitive.
Because the definitive project of the bridge can change
The final project is not actually not. The final drafting of the documents will take place in the executive phase, in which the designers will have to insert changes and reviews according to the requests of the Ministry of the Environment and the Scientific Committee of the Strait of Messina.
During the environmental impact assessment procedure, the Ministry specified that it must be deepened “in the executive design, the evaluation of the seismic danger, through the Site-specific analyzes and updated models.”
In addition, it is asked to verify “potentially interfering active faults with the track or foundations, even if not relevant on a national scale”.
The bridge over the strait “is not feasible”: it is written in the project cards
The Scientific Committee also asked to update and complete the “geological-structural” and “seismic microzonation” framework, inviting to evaluate interference with possible active faults.
The Strait of Messina has always stated that “the points of contact with the soil of the work, on the basis of the geosismottonic studies performed, have been identified avoiding positioning on active faults”. However, in the project you can see more.
The fault under the pylon of the bridge: the “Cannitello” problem
As mentioned, the “enters” fault system in Calabria. The works of the final project emerged the “problem” of Cannitello, on the Calabrian side. Here, the pylons of the bridge will arise. Twenty meters away, underground, there is an active tectonic fault.
A study commissioned by the Municipality of Villa San Giovanni, and signed by the engineer Paolo Nuvolone, says that under the 400 -meter high Calabrian pylon, in Cannitello, there would be a “capable” fault. Carlo Doglioni, former president of the National Institute of Geophysics and Volcanology, and other experts have invited new insights to the area to establish more precisely the characteristics of this system.
The Strait of Messina and its CEO, Pietro Ciucci, have instead repeatedly stated that all the faults under the bridge and in the area have been surveyed and monitored. But updates and clarifications are expected in the executive project.
Bridge on the Strait of Messina: all the investigations and news
There is still much that we don’t know about the bridge over the Strait of Messina. New details will gradually emerge that the project will go on, as established by the law that has “resurrected” the bridge, with methods criticized not only by those who are against the construction of the work but also by the President of the National Anti -Corruption Authority, Giuseppe Busia, who repeatedly expressed his doubts to Dossier The Vermilion, still not clarified.
Read the other investigations by The Vermilion Dossier.it