“This type of earthquake can last many months, even up to a year”

In southern Turkey, it rains it pours.

Thomas Osborne
Thomas Osborne
22 February 2023 Wednesday 04:24
9 Reads
“This type of earthquake can last many months, even up to a year”

In southern Turkey, it rains it pours. After the largest earthquake that the population remembers, two more tremors, measuring 6.4 and 5.8 degrees, were registered late Monday afternoon in the province of Hatay, leaving 6 dead and hundreds injured, according to the Ministry. of the Turkish interior. With these new images of devastation, the question that prevents many from sleeping is: How long can earthquakes last? In other words, when will all the people who have abandoned their homes be able to return home? We try to answer some questions.

While it is very common for milder aftershocks to occur in the days after a major earthquake, it is difficult to understand why they occur and what exactly is the relationship between them. According to Goula, after a first tremor, we can find ourselves with two extreme situations: that "excitation phenomena occur in the adjacent faults that trigger more earthquakes" or that "there is a single rupture". "In this case, the segments that have remained unbroken on the fault break over the following days with smaller magnitude earthquakes," says Goula. However, usually a combination of the two scenarios occurs.

Mainly, because the tremors on Monday had a smaller seismic magnitude than the initial earthquake, since they were aftershocks. The magnitude of the initial telluric movement was 7.8, while that of the earthquakes registered on Monday was 6.4. According to Xavier Goula, an expert in earthquake resistance, "the difference of one and a half degrees of magnitude is enormous. The size of the rupture of the fault where the displacement occurs is much higher. In the last earthquake, the rupture may have been 10 or 20 kilometres, while on the 6th it was around 200 kilometres".

In addition, the affected area was already largely evicted and only "rescuers and residents trying to recover their belongings" remained, according to the mayor of the Antakya metropolitan conurbation, Lütfü Savas.

It is true that some media outlets warned about the possibility of a tsunami occurring on Monday, because the epicenter of the shock was very close to the coast, something that could have affected hundreds of displaced people who are in camps on the coast. "Earthquakes trigger tsunamis when the rupture occurs below the sea floor or very close to the coastline, and in this case it was very close to the coast," Goula explains. However, Goula adds that "if there were to be a tsunami we would already know, because the wave takes only a few seconds to originate after the tremor."

Unfortunately, it is very difficult to obtain reliable data for the prediction of future earthquakes, although aftershock models are becoming more complex. According to Xavier Goula, this type of earthquake "can last for many months, up to a year." "We have to look at similar phenomena such as the seismic crisis that occurred in Italy in 2019, which lasted almost an entire year," he explains. a destructive seismic series in Girona lands during the Middle Ages, which began in March of the year 1427 and the strongest shock of M6.5 did not occur until the following February.

We are currently at a fundamental moment to determine this: once the search and rescue tasks have been completed, a quick diagnosis of the buildings is carried out to verify that they offer the necessary security. This process can take several weeks, depending on the area. People whose buildings meet the requirements will be able to return, but the rest will have to wait. President Erdogan, in the run-up to the electoral campaign, promised to rebuild new buildings to replace the thousands destroyed, within a year in the ten affected regions.

In order to speed up this process, the Association of Structure Consultants will collaborate with the French Association of Earthquake Engineering, in training Syrian professionals in the recognition of buildings in order to return to a normal situation as soon as possible. In fact, both associations carried out a training session for structural technicians last week to be prepared in the event of an earthquake in Andorra.

Because the Arabian plate, which is moving north, and the Anatolian plate, which is moving west, at considerable speed, meet there. "It is a zone of friction between tectonic plates, which is why earthquakes occur quite frequently," says Goula. Examples of this are the earthquake that hit Istanbul in 1999 with a magnitude of 7.6 or the one in 1939, which caused more than 30,000 deaths.