Paris:

The Highly Effective Earthquake that struck Morocco, killing greater than 2,000 individuals, did not hit in essentially the most energetic seismological area, mentioned one French skilled. However aftershocks might be anticipated, he warned.

Philippe Vernant — a specialist in energetic tectonics, notably in Morocco, on the College of Montpellier — answered AFP’s query’s on the devastating quake.

– Was the Morocco quake a shock? – 

Morocco is a kind of international locations the place the query isn’t whether or not there will likely be earthquakes.

The Agadir earthquake (magnitude 5.7 in 1960) destroyed your complete metropolis and killed virtually 15,000 individuals, and extra not too long ago there was the Al Hoecima earthquake (magnitude 6.4 in 2004), additional out on the Mediterranean. 

Trying additional again in historical past, there have been earthquakes within the 18th century, in all probability round magnitude 7 within the Fez area. 

The epicentre of the latest quake isn’t in essentially the most energetic space of Morocco. However there are the Excessive Atlas mountains… The sort of earthquake is what results in the rise of the Excessive Atlas vary.

– Was the Morocco quake just like the one in Turkey in February? –

In Turkey, we had horizontal motion, as a result of Turkey is shifting to the West, shifting in direction of Greece. There was a horizontal sliding of the (tectonic) plates. 

Right here, we’re seeing extra of a convergence between Africa and Eurasia or Iberia, the Spanish half, and overlapping faults… However we’re nonetheless coping with plate boundaries.

– What explains the violence of the Morocco quake? –

We have to see what magnitude the earthquake will likely be. We’re speaking about 6.8 or 6.9, which is kind of robust. 

This corresponds roughly to a median displacement on the fault line of round one metre in a couple of seconds, over a number of kilometres.

Clearly, this shakes the area enormously. 

Then there’s the depth: at first it was estimated to be at round 25-30 kilometres, but it surely appears to be going again up, nearer to 10 kilometres. 

The nearer you get to the floor, the higher the impact of the rupture. 

That is what occurred in France in 2019 within the Teil area within the (southern) Ardeche area. It was a “small” earthquake, however because it occurred at a depth of only one kilometre, it shook issues up so much.

– Ought to we anticipate aftershocks in Morocco? –

Aftershocks are certain to happen.

Even when they’re much less robust, they will result in the collapse of buildings already weakened by the earthquake. 

Historically, we are inclined to say that aftershocks diminish in depth.

However in Turkey, one earthquake triggered one other. The primary tear can result in the rupture of one other fault by way of a cascade impact, which is why there’s generally a danger of a stronger earthquake after the primary one.

– Is it attainable to foretell this type of occasion? –

Sadly, we won’t predict something. 

We attempt to estimate recurrence intervals in accordance with the completely different magnitudes of the earthquakes, however then the behaviour might be chaotic, with two robust earthquakes over a brief interval after which nothing for a really very long time.

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