Nice-Première: An earthquake on September 2, another on October 24. As a keen observer of seismic phenomena, should we be concerned about these two earthquakes occurring close in time? Is there a fear of a more intense one happening soon without resorting to excessive catastrophizing?
André Laurenti: Despite all investigations and more modern observations, we still cannot predict earthquakes. However, for our region, for a few decades now, seismologists in the French Riviera have recorded an earthquake with a magnitude greater than 4 on average every five years. The last one occurred in February 2001, so we are within the timeline for the next one. Should we assume that the two events on September 2 and October 24 correspond to this recurring activity? It’s hard to say—the first had a magnitude of 4.2, the second 3.8, values lower than those observed so far. We will have to wait a bit longer to draw conclusions. In the meantime, this does not mean we will be at peace for five years.
NP: It’s known: the French Riviera is an active region. What are the actual numbers? How many significant earthquakes (above 3 or 3.5 magnitude) are recorded per year?
AL: Although in recent years, the Pyrenees have recorded more activity than the French Riviera, the Alpes-Maritimes and Liguria stand out for their relatively rich seismic history. From the 14th to the 17th century, about six destructive events marked the country’s history, with a series of “endemic” epicenters located in the Vesubie Valley area, north of Nice. Later, in the 19th century, Liguria was the scene of four destructive earthquakes, the latest being on February 23, 1887, which caused significant damage in Liguria and also in the Alpes-Maritimes. Regarding more recent seismicity, the many sensors deployed in the region (about fifty) record the slightest tremors of the earth.
Launched in January 2002, the Azurseisme website focuses on the seismic activity of a vast area of approximately 28,200 km². The study zone covers three French departments, including the eastern part of Alpes de Haute Provence (active) and Var (less active) and the entire Alpes-Maritimes. On the Italian side, it includes the western part of Liguria and the southwestern part of Piedmont. In this area, since the year 2000, an average of five earthquakes with a magnitude of 3 or greater have been recorded annually.
NP: You have researched the impact of tremors on regional buildings. What findings have you made?
AL: Generally speaking, since the early 20th century, the vulnerability of ancient buildings in the hinterland has steadily increased. A process intensified after the two wars due to rural exodus. Many buildings have been abandoned, some demolished, creating gaps in the urban fabric. Today, with modern life and a choice of materials not always well-suited, buildings are not only poorly maintained but also subject to modifications that weaken them. Ancient buildings are sometimes still transformed by altering the load-bearing structure without the involvement of architects or engineering firms.
Nowadays, whether in villages or the historic centers of our cities, major changes have been made in places to accommodate commercial needs or simply for garages. All of this disrupts the original organization of facade walls and only weakens the building.
The addition of reinforced concrete can also pose serious problems. Indeed, introducing extremely rigid concrete elements into a wall made of small stones bound with lime can have the opposite effect to that desired, which is to say, increase vulnerability, as under seismic stress, these concrete elements could act like a battering ram, leading to partial or sometimes total collapse of the structure.
Another issue is adding floors with rigid structures laid on original, therefore flexible and different materials, inadvisable unless the entire structure is supported from the base. It is, thus, advisable during repairs to conduct a vulnerability assessment and schedule reinforcement interventions alongside comfort works.
NP: Do these small tremors have any effect on buildings?
AL: The small tremors regularly recorded in the region generally do not affect structures except in areas very close to the epicenter and for magnitudes above 4. This was the case on April 21, 1995, with a 4.7-magnitude earthquake that caused the awning of the San Bernardo chapel to tilt in the Roya Valley. Some buildings were also slightly cracked in Airole in the same valley.
NP: Do the political authorities and citizens in the Alpes-Maritimes have a good understanding of the seismic risk?
AL: Referring to the Lisbon earthquake of 1755, writer Jean-Jacques Rousseau, in his “Letter on Providence,” expressed his viewpoint by stating that “man can act to improve his existence.” This observation marks the beginning of reflection on man’s responsibility towards major natural risks, previously attributed solely to fate. In the Alpes-Maritimes, one could lament a certain inertia. Just over a decade ago, earthquakes were still a taboo topic, and many experts faced significant challenges. Politicians and scientists preferred discretion over divulgence on this topic. There were two reasons for this: the fear of creating panic and the lack of sufficiently reliable data. Nowadays, things are changing, seismology, a still emerging science, has made significant advances, alongside a better understanding of historical seismic activity.
I believe the authorities are somewhat more convinced that, in the event of a disaster, it is better to have informed citizens than panicked ones. Despite the recurrence of destructive earthquakes worldwide, notably the one in Sumatra in December 2004, it must be recognized that, despite efforts in schools, little progress has been made in “raising awareness” among the general public in the Alpes-Maritimes, and enormous efforts are still needed in this regard.
NP: You have released a new book, “The Alpes-Maritimes Listening to Earthquakes.” What are your conclusions?
AL: Except for the overseas departments, the Alpes-Maritimes is one of the most earthquake-prone departments. The historical seismicity, with its share of destructive events, is evident proof. To tackle such unpredictable disasters, local leaders should continue to support research projects through subsidies. More is needed because a lot still needs to be done, especially regarding public awareness, information dissemination, and effective measures to reinforce ancient buildings. It is essential to communicate and build trust with the population and all local actors and partners.
As earthquakes increasingly demonstrate, the real priority should now be on existing structures. Because even if we might claim that new constructions are less vulnerable due to their typology and the kind of earthquakes we face, this is not the case with ancient buildings. Analyzing and addressing the problem of old buildings is an essential program. Given the urgency of the situation, adhering to a few simple principles mentioned in the book could save lives.
In the absence of specific regulations, it would be desirable for politicians and local authorities to assume their responsibilities fully, launching priority actions. Doing nothing would be criminal.
Soil instability, characterizing our region, generally causes significant building disorders in the event of an earthquake. Consequently, it is necessary to take basic precautions in choosing the land, foundations, and building rigidity. I hope the work presented through my two books and the “Azurseisme” website will not leave the leaders and decision-makers of the French Riviera indifferent.
We are all affected by this scourge. One only needs to think about future generations who will live in the world we leave them! It’s crucial to remember that governance involves foresight and that good prevention costs significantly less than a catastrophe.
NP: Finally, why is a municipal employee of the city of Cagnes-sur-Mer passionate about earthquakes?
AL: This passion has absolutely nothing to do with my professional activity. My job in the city at the design and project department provides a livelihood; my investigations into seismic activity take second place.
In fact, the idea for such an interest sprouted in April 1989 on the lips of one of Stromboli’s active mouths. I was accompanied by a volcanologist guide, Guy de Saint-Cyr, a volcano enthusiast, and a few friends when we suddenly found ourselves mesmerized by a gigantic curtain of fire erupting from the earth’s bowels. I still remember it as if it were yesterday. Faced with such a spectacle of terrible beauty, one cannot remain indifferent; such a vision marks a man’s life somehow, so something had to be undertaken upon my return.
Certainly, traces of volcanism exist on the French Riviera, but they are, to my taste, far too ancient to be of interest. Hence, I turned to a substitute subject: the study of regional earthquakes.
I immediately delved into archive research, enabling me to accumulate substantial documentation. Then, by engaging in a wholly unknown and delicate field, I quickly realized the significant gaps in information regarding the region’s seismic past, and the idea arose to write to properly chronicle the timeline of earthquakes.
In 1993, I had the opportunity, while attending a conference in Vernegues (Bouches du Rhone), to meet specialists, which helped in better directing my work and furthering my investigation within the European University Center of Ravello’s multidisciplinary programs, dedicated to the vulnerability of old buildings in seismic zones, a program under the Council of Europe’s EUR-OPA Major Natural and Technological Hazards Agreement.
In February 1998, I published my first book, “The Earthquakes of the Alpes-Maritimes – History and Awareness,” mainly focusing on the chronology of destructive events. Four years later, in January 2002, the site [https://www.azurseisme.com](https://www.azurseisme.com) was launched online. Since late October 2006, it has surpassed 247,000 visitors, which is not negligible for such a subject. It is essentially an educational tool on the region’s seismic past and perfectly addresses a need.
At the end of February 2006, I published a second book, “The Alpes-Maritimes Listening to Earthquakes.” Additionally, I am a member of the A.P.S. group (Archaeology, Pathology, Seismicity) located in Perpignan. This multidisciplinary association gathers numerous experts, and we meet every two years to present our work. Finally, for the past three years, I have been offering lessons for the professional master’s degree program Arch’ heritage (“architectural heritage restoration”) at the University of Nice Sophia-Antipolis.
Today, there remains much work to be done on historical issues, on the issue of old buildings situated in seismic zones, and on raising public awareness. Personally, I am increasingly challenged to juggle between my primary role and this side activity that takes up more and more time. I am desperately chasing after free time and hope for the 35-hour workweek to continue. I use these precious additional days to participate in conferences or give talks on the subject.
Book List:
[https://www.azurseisme.com/Ouvrage.htm](https://www.azurseisme.com/Ouvrage.htm)
Gallery Images:
1. A vulnerable building in La Bollène-Vésubie
2. André Laurenti (photo Nathalie Chasseriaux)
