A French expert has warned of aftershocks in Morocco as a devastating 6.8-magnitude earthquake hit the country on Friday, killing at least 2,012 people and injuring 2,059, with more than 1,000 in critical condition.
The earthquake struck in the High Atlas Mountains southwest of the city of Marrakech, damaging historic buildings in the city closest to the center, while the worst-hit areas were in the nearby mountains.
Philippe Vernant, an expert on active tectonics at the University of Montpellier, told JEE News that Morocco is one of those countries where there is no question whether earthquakes will occur.
The Agadir earthquake (magnitude 5.7 in 1960) destroyed the entire city and killed about 15,000 people, and more recently the Al Hoceima earthquake (magnitude 6.4 in 2004) in the Mediterranean.
Looking further back in history, in the 18th century, there were probably 7 magnitude earthquakes in the Fez area.
The epicenter of the recent earthquake is not in the most active region of Morocco. But there are the High Atlas mountains… This type of earthquake caused the rise of the High Atlas range.
Morocco earthquake like Turkey?
In Turkey, we had a horizontal movement, because Turkey is moving westward, moving toward Greece. There was horizontal sliding of (tectonic) plates.
Here, we’re seeing more convergence between Africa and Eurasia or Iberia, the Spanish part, and overlapping faults… but we’re still dealing with plate boundaries.
Why was the Moroccan earthquake so violent?
We have to see how strong the earthquake will be. We’re talking about 6.8 or 6.9, which is quite strong.
This corresponds to an average displacement of more than several kilometers, in a few seconds, on a fault line of about one meter.
Obviously, this has shaken up the region a lot.
Then there is the depth: at first it was estimated to be around 25-30 km, but it seems to be going back to around 10 km.
The closer you get to the surface, the greater the impact of the explosion.
This is what happened in France in 2019 in the Telle region of the (southern) Ardeche. It was a “small” earthquake, but since it was only about a kilometer deep, it shook a lot.
What about aftershocks in Morocco?
Aftershocks are bound to come.
Even if they are less strong, they can cause weak buildings to collapse before an earthquake.
Conventionally, we say that aftershocks decrease in intensity…
But one earthquake in Turkey triggered another. The first tear can lead to the rupture of another fault through a cascade effect, which is why the first one is sometimes followed by a strong earthquake.
How to predict earthquakes?
Unfortunately, we cannot predict anything.
We try to estimate the recurrence intervals for the different magnitudes of the earthquakes, but then the behavior can be chaotic, with two strong earthquakes in a short period and then nothing for a very long time.
