The definitive project of the bridge over the Strait of Messina says verbatim: “The bridge and the ground connections are capable of withstanding: earthquake of magnitude 7.1 Richter”. You can read it on the web page of the Stretto di Messina company. That’s right: it “resists” (photo below, taken from the presentation). But we don’t want to worry about spelling. We are instead interested in that number: 7.1, which represents the intensity of the earthquake that devastated the north-eastern end of Sicily and part of Calabria in 1908. This value is fundamental because, in the case of a strong earthquake, it establishes whether the new 16 billion bridge will collapse into the sea with cars, trains and people. Or it will stay standing. The official presentation of the final project continues as follows:
“The seismogenic potential of the Strait area – say the designers – is not capable of producing earthquakes of a magnitude higher than that of the design considered for the bridge (7.1 Richter scale)”. And again: “With an earthquake of this magnitude, the bridge remains in the elastic field, i.e. it does not suffer damage, therefore maintaining further safety margins beyond the expected threshold”. And then again: “Decades of studies have determined the consolidation of knowledge on the 1908 earthquake (7.1 Richter) and the main fault that generated it, classifying it as an extremely rare event, with return times of over two thousand years”.
Yet, according to a study published by ten Italian scientists five years before the presentation of the final project, all these assessments – vital for the safety of the bridge – are incorrect. Let’s see why below.
First point. The return times of earthquakes are a conceptual simplification: if today I fall down the stairs and it has never happened before, my falls have a return time of once every 58 years (my age). That doesn’t mean I can’t fall again tomorrow and hurt myself. But there would be something even more approximate in the final project: what is scientifically denied is in fact that value of 7.1, as the maximum possible magnitude of an earthquake in the area where the bridge is to be built. The statement by the Strait of Messina company, according to which “the seismogenic potential of the Strait area is not capable of producing earthquakes of higher magnitude”, in fact, would not correspond to the truth (photo below).
Because the magnitude of an earthquake is a vital factor for the bridge
Magnitude is the quantity that relates to the quantity of energy transported by a seismic wave: the higher the magnitude, the higher the destructive energy released by the earthquake. But what then is the maximum possible magnitude in the Strait of Messina area?
The further challenge, in this case, is given by the need to cross the Strait of Messina with a road and railway viaduct with a single suspended span: 3300 meters long, supported by two 399 meter high towers with 4 1.26m cables meters in diameter. And it will not be a perennial work, like certain Roman bridges that are still efficient today: the expected useful life is 200 years. But let’s get to the document that demolishes the project, as it has been conceived so far.
Who are the scientists who deny the final project
On 17 September 2019 – therefore five years before the controversies of recent days and three years before the appointment of Giorgia Meloni’s government – ten Italian scientists published in the journal of the European Geosciences Union a study entitled: “From mapped faults to seismic magnitude based on fault length: a test on Italy with methodological implications”. It is a university collaboration between Sapienza University of Rome, the National Research Council (Cnr), the National Institute of Geophysics and Volcanology and Sogin, the public company that manages nuclear plants. The first signature is Sapienza professor Fabio Trippetta. At the end of the list of authors, Carlo Doglioni, president of the National Institute of Geophysics and Volcanology (Ingv) and vice-president of the prestigious National Academy of the Lincei.
The study analyzes the relationship between the dimensions of a series of seismic faults (fractures along the Earth’s crust) and the magnitudes of the earthquakes they triggered over time. The objective is to estimate, starting from the size of the faults known so far, the maximum possible magnitude of an earthquake in a given territory.
The result is obviously not able to predict when the next earthquake will occur. It cannot therefore be used for civil protection purposes. But it can provide fundamental information to designers of strategic works. The map published in the research by Doglioni and Trippetta demonstrates that, based on the dimensions of the active faults, in the Strait of Messina area the earthquakes do not stop at values of 7.1, but can reach magnitudes above 7.5 (the red colors in the photo above, taken from the study).
The Panza-Rugarli law and why it is important for the bridge over the Strait
The data is also confirmed by what is called the Panza-Rugarli law, from the name of the Trieste geophysicist Giuliano Panza, academician of the Lincei and one of the most important scholars in the world, and the structural engineer Paolo Rugarli. The Panza-Rugarli law in fact demonstrates that the maximum design magnitude of the earthquake (the one that must be considered for the bridge over the Strait to resist), given the current state of knowledge, “can be set as equivalent to the sum between the maximum magnitude and 0, 7” (Earthquake Science, Elsevier, 2024).
Therefore, the maximum magnitude measured (so far) of 7.1 for the 1908 earthquake in Messina should be added to the margin of 0.7: thus obtaining the maximum credible earthquake value of 7.8 Richter. Magnitude that coincides with that suggested by the dimensions of the faults that cross the area between Sicily and Calabria. The difference of a few decimals should not be deceiving: the destructive energy released by a 7.8 magnitude earthquake is approximately twenty times higher than the already catastrophic energy of a 7.1 earthquake. In other words, the new bridge could suffer irreparable damage. Or fall into the sea, with all the people who would be crossing it at that moment.
The earthquake twenty times stronger that was not considered in the project
It should also be taken into account that in 1908 the measurement of the intensity of such a destructive earthquake could not be precise. And it wouldn’t be today either. But already in recent months, as soon as the Minister for Infrastructure, Matteo Salvini, relaunched the project of the bridge over the Strait, the scientific community had noticed that the seismic evaluation was missing a fundamental piece of data: the calculation of the margin of error. Every measurement, to be scientifically valid, must in fact always be accompanied by the calculation of the possible error. The European seismographic network in the early twentieth century was flawed by greater approximation. And precisely for this reason, considering the due margin of error, the earthquake of the last century in Messina could have easily exceeded the magnitude of 7.1.
The higher the maximum possible magnitude, the higher the construction costs of the work: concrete, steel, foundations, aerodynamic structures must be adapted to the new intensities of stress. Obviously Minister Salvini is not a scientist. He certainly trusted the managers appointed by his ministry. But between 20 October 2023 and 20 January 2024, the final project, according to the documents that Today.it publishes (photo above), was drawn up, verified and approved four times by three professionals. With the signature of Pietro Ciucci, CEO of the Ponte sull’Sretto di Messina company, owned by the Ministry of Economy and Anas. And that of Flavio di Pietro, CEO of Eurolink, the joint-stock consortium of the companies to which the work was entrusted. But evidently none of them were aware of the CNR and INGV studies. Even though they have been public for more than five years.
The bridge over the Strait “is not feasible”: it is written in the papers – by Cesare Treccarichi
The serious words of the president of the National Institute of Geophysics and Volcanology, confirmed by the study that Today.it has found, cannot be ignored. Neither by the minister, nor possibly by the accounting judiciary. “Building the bridge over the Strait is a political choice – says Carlo Doglioni to Corriere della Sera -. But such an expensive and complex work can only include an assessment of the maximum possible seismic danger. The numbers speak for themselves here: the current project contains parameters too low”.
Read the other news from Today.it on the bridge over the Strait of Messina