The earthquakes that hit southern Turkey and northern Syria earlier this week came as no surprise to seismologists, who for decades have known the region offers a fragile and favorable seismic environment. to this kind of tragedy.
But, despite this detailed knowledge of the networks of faults in the earth’s crust at this location, the forecast of these last tremors, which would have made it possible to prevent human losses now amounting to tens of thousands, was still and always an impossible mission. for these specialists in plate tectonics. These scientists admit, tragedy after tragedy, to finally be overwhelmed by the complexity of the phenomenon.
“Predicting an earthquake with precision, where it’s going to happen, at the exact time and with the magnitude it’s going to have, I’ve never seen that and I don’t think I’ll see that in my lifetime, ”drops in videoconference Christine Goulet, director of the earthquake research center of the United States Geological Survey (USGS), the American geological agency and world reference in terms of earthquakes. The duty joined her in Los Angeles this week. “It is still very difficult for us to understand and measure the parameters of such a phenomenon, which is why we can only make probabilistic forecasts over long periods and over large territories, but never anything very localized and , above all, nothing in the short term. »
For seismologists, it was therefore impossible to see coming the first rupture on the East Anatolian fault which occurred on February 6 around 4 a.m., west of the city of Gaziantep, in Turkey, then the 54 aftershocks measured by the USGS in the following 12 hours. And this, despite the analysis of thousands of earthquakes over the last 50 years, the existence of networks of wave sensors in the ground and even the recent use of artificial intelligence to manage the complexity of calculations of data.
“This artificial intelligence is a new tool in our trunk, explains Mr.me Goulet, but for the moment, it helps us above all to understand an earthquake once it has occurred, but not in the moments preceding it. These algorithms must be trained by data of which we still have too little quantity. Our understanding of earthquakes is on a human scale, it spans barely a hundred years, whereas the phenomenon is inscribed on a geological scale which takes place over millions of years. »
chance dominates
This partly explains this, but also the hazardous attempts to predict earthquakes that have marked the recent history of seismology. We remember: in 1985, the USGS announced that in January 1993, a magnitude 6 earthquake was going to occur on the San Andreas fault, in the Parkfiled region of California. And this, with a level of confidence established at 95%, had assured the agency at the time.
The rupture finally occurred, without warning, on September 28… 2004, indeed on the segment of the fault determined by the scientists and with the correct magnitude, but 11 years later.
By studying radon emissions, electromagnetic waves and even the behavior of animals, several researchers had also succeeded, in the 70s and 80s, great decades of the quest for earthquake prediction, in establishing certain lines common to these seismic phenomena. . None has succeeded in supporting consistent and, above all, repeatable prediction models that would have saved the 100,000 lives killed by the Kashmir earthquake in 2005 or the 300,000 lost in the earthquake that struck Haiti by surprise in January. 2010. To mention but a few.
Between 1998 and 2017, earthquakes were responsible for more than half of natural disaster-related deaths worldwide, according to the World Health Organization (WHO). A report fueled by the Turkish-Syrian tragedy of the last few days and whose mathematics, which exceeded 22,000 deaths on Friday according to the last provisional count, was ultimately not a fatality, estimates Mme Goulet.
Our understanding of earthquakes is on a human scale, it spans barely a hundred years, while the phenomenon is inscribed on a geological scale which takes place over millions of years.
“For researchers in seismology, earthquakes and earthquake engineering, it is always extremely painful to witness these building collapses, such as those we have seen in Turkey, and the human tragedies that come with them, says the scientific, because even if we are not able to predict the moment of the earthquake, we know very well how to prevent its consequences. »
According to her, the Izmit earthquake in Turkey in 1999, killing nearly 18,000 people, had nevertheless led to changes in the country’s building code, so as to prevent these tragedies from occurring. “But this code only works when it’s put into practice, which it didn’t seem to be the case,” she said. We have seen visibly recent constructions collapse. These inexpensive constructions, in lightly reinforced masonry and little or unreinforced concrete, are solid as long as a simple jolt does not weaken them. However, these are constructions that are very widespread throughout the world, including in seismic zones where more suitable buildings are needed. »
Prevent, but after
In the absence of more predictability in the face of the appearance of earthquakes, scientists can however count on nascent networks of alerts making it possible to warn people exposed to a rupture in an seismic fault. But only after the first sudden slip along the fault plane, causing an earthquake.
“It’s the best we can do,” says M.me Goulet, referring to the ShakeAlert system deployed on the west coast of the United States. Canada is currently working on its own for the western regions, but also Quebec and Ontario, where the probability of earthquakes is highest. “These systems trigger once the earthquake has started and can give people who receive the alert on their phone the 10 or 20 seconds of time needed to seek shelter. But these are expensive systems to put in place and which very few countries have. »
Rural Turkey hit by the latest earthquake, like Syria grappling with a lingering civil war, was not among them.