2023-09-12 18:45:57
RICARDO F. COLMENERO
Updated Tuesday, September 12, 2023 – 18:45
They discover under the mountain range an anomalous, hot and not very dense mantle related to the Quaternary volcanism of the region
A woman in Amizmiz, at the foot of the High Atlas mountain range.CARLOS G. POZO
If in 25 million years there are any of us left around, we would see that Morocco has collided with Andaluca and the Strait of Gibraltar has been closed. The African tectonic plate would continue to push the Eurasian plate and, if geologist Christopher Scotese is right, The Iberian Peninsula will begin to rotate clockwiseand in another 25 million years northern Spain will collide with the French coast.
For now, it is certain that the Eurasian and African plates They have been pushing each other for millions of years, like a plasticine puzzle in which the pieces mix, or rise, or submerge, causing thousands of earthquakes a year. The last one, this weekend at the Atlas mountain range, with the epicenter more than 700 kilometers from the collision of tectonic plates. “It is not predictable, but not impossible“, points out seismologist Juan Vicente Cantavella, from the National Geographic Institute (IGN). The Agadir earthquake, at the ocean mouth of the mountain range, and even further away from the plate collision, was 5.8 and in 1960 it stopped at 12,000. to 15,000 fatalities.
At 11:11 p.m. on September 8, the earth trembled 60 kilometers away. southwest of Marrakechand in Spain the IGN received more than 500 noticesmostly from Andaluca, but also from Madrid and the islands of La Palma and El Hierro.
According to a study of the Atlas faults published in 2006 by researchers from the Tectonics Laboratory of the Pierre et Marie-Curie University, the Paul Czanne University of Marseille, the Mohamed V University of Rabat and the Cergy Pontoise, the Atlas faults really”potential to generate earthquakes of between 6.1 and 6.4″ maximum on the Richter scale. They fell short, which makes it more difficult to predict if there will be more, when, and of what magnitude.
Itahiza Domnguez, IGN seismologist, explains on social networks that seismic hazard maps have “a problem”: they are based on knowledge of the past, but if this is limited, or the recurrence times of earthquakes are long, the danger can be “underestimated”. And this is believed to be what happened with the Moroccan earthquake, since the pre-existing map gave a lower probability in the hypocenter area compared to other points in the country, and in general in northern Africa. In the Ibrian Peninsula, the most dangerous points are in the provinces of Granada and Murcia. In the first, an earthquake of 6.7 in 1884 with a balance of more than 1,000 deaths. Lorca’s in 2011 was 5.1 and caused 9 deaths and more than 300 injuries. For this reason, Itahiza Domnguez indicates that “it is not ruled out” that a new “destructive” earthquake will occur.
Six earthquakes in Morocco
Although in principle the epicenter was located in a fault north of the Atlas, now it’s not so clear either. “The focal mechanism does not match, and it could be a fault in the southern Atlas. We are using five stations, but the closest one to the earthquake East a 150 kilmetros“, explains Cantavella.
Nineteen minutes after first earthquake a replication of 5.1 was produced. And at 1:21 in the morning the third, 4.6. The next one arrived at 8:38, 4.2. The next one 22 minutes later, also 4.2. And the sixth at 12:19 noon, 4.1. The earth trembled on both the northern and southern fault lines of the Atlas mountain rangeas if they were having a seismic conversation, which was leaving mortal victims wherever buildings had been built: Al Hauz, Taroudant or Chichaoua.
Scientists from the University of Granada (UGR), belonging to the Andalusian Institute of Earth Sciences and the Department of Geodynamics in collaboration with the University of Jan and Moroccan universities, believe that there is a “high possibility of aftershocks of the earthquake for months”, and that of course they will be felt again in our country.
These seismic movements narrow and raise the mountain range at a rate of 0.1 millimeters per year, according to the same study by Franco-Moroccan universities. More recent geodetic measurements obtained with millimeter-precision GPS records show that The Atlas is narrowing at a rate of one millimeter per year, which according to UGR scientists, contrasts with its low seismicity. At the same time, at 700 kilometers, the Strait of Gibraltar is narrowing at a rate of between 4 and 25 millimeters per year, as a consequence of the same plate movement.
The geophysical and geological studies carried out by his team show that under the continental crust they discover an abnormal, hot and not very dense mantle that supports the relief of this mountain range, and is related to the Quaternary volcanism of the region. In a few months we will know if textbooks should correct the 4,167 meters of Toubkal, the highest peak in the mountain range.
According to the model developed by the US Geological Survey, the morocco earthquake It was produced by the displacement on a fault surface about 30 kilometers long (horizontally) by 20 kilometers wide (in the direction of dip of the fault towards the interior of the Earth). It produced a 1.5-meter rupture, which began about 25 kilometers deep, and propagated radially, until it stopped about 10 kilometers from the Earth’s surface.
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