The epicentre of Morocco’s devastating earthquake on 8 September was within the Excessive Atlas Mountains, about 71km south-west of Marrakesh. Moina Spooner, from The Dialog Africa, requested Jesús Galindo-Zaldivar, who has been finishing up analysis on the formation of the Atlas mountains and the geology of the realm, in regards to the elements which led to this case.
What analysis have you ever been doing in Morocco’s Atlas Mountains?
The Atlas Mountains are an interesting vary in north-west Africa, spanning Morocco, Algeria and Tunisia. They’re located south of the principle Eurasia and Africa (Nubia) tectonic plate boundary.
This space doesn’t normally have a whole lot of earthquakes in comparison with different locations close to the sides of tectonic plates, the place the actions of plates will trigger intense seismic exercise. However in 1960 the Agadir earthquake triggered a whole lot of harm and lack of life.
I’m a part of a workforce of geologists, geophysicists and geodesists from numerous Moroccan universities and Spanish establishments finishing up analysis within the space. We wish to perceive this mountain vary’s growth and its place on the fringe of a continental plate boundary. Research of seismic exercise, gravity and different geophysical phenomena permit us to grasp the Earth’s deep construction, all the way down to depths exceeding 100km.
Via discipline geological analysis, we will detect and analyse faults – fractures or cracks within the Earth’s crust alongside which there was motion. These actions could be horizontal, vertical or diagonal, and so they happen as a result of immense forces appearing on the Earth’s tectonic plates.
Lastly, utilizing geodetic strategies (GPS recordings) we’re capable of decide how tectonic plates are transferring. That is performed by often measuring benchmark websites with millimetre accuracy.
What has your analysis discovered?
Our analysis reveals that the Atlas Mountains had been shaped throughout the break-up of the Pangea supercontinent. It’s now a mountain vary that’s actively rising, as evidenced by its excessive peaks and steep slopes.
The steep slopes of the mountains and the straight traces the place the Earth’s crust has cracked recommend that there was current motion within the Earth beneath this space. It’s stunning that there aren’t extra earthquakes right here.
The Atlas Mountains are getting pushed collectively at a fee of about 1 millimetre every year. This occurs as a result of the Eurasian and African plates are transferring nearer to one another. This squeezing motion is accountable for creating the tallest mountains within the space, the southern fringe of the place these two huge plates meet.
What do your findings let you know about this earthquake?
The catastrophic earthquake passed off to the north of the western Atlas mountains, south of Marrakesh. Based on estimates by Morocco’s Nationwide Institute of Geophysics and the US geological survey, the depth is between 8km and 26km.
The earthquake resulted from a geological phenomenon referred to as a “reverse fault”. This happens when tectonic plates collide, inflicting the Earth’s crust to thicken. The stress alongside these fault traces can induce earthquakes as rocks abruptly shift to launch amassed stress, which is attribute of a seismic fault.
The 6.8 magnitude implies that the fault accountable for this earthquake might be round 30km lengthy. This estimate takes into consideration the relationships between energetic fault size and earthquake magnitudes.
So, why don’t we see many earthquakes on this space, though it’s a spot the place the tectonic blocks are transferring and the mountains are rising? Earthquakes occur when there’s a sudden shift in rocks alongside a fault line, attributable to the discharge of saved power that’s been increase over time. On this area, there haven’t been any main recorded earthquakes earlier than, which means that the stress from the plates pushing collectively has been increase deep underground for a very long time. When the stress obtained an excessive amount of for the fault to deal with, it triggered an earthquake.
On this mountain belt faults won’t produce earthquakes fairly often. After the earthquake, the rocks within the space moved and adjusted, however different close by faults may now be underneath further stress, and so they might produce smaller earthquakes often called aftershocks which may proceed for months and even years.
What ought to authorities be doing to arrange?
Earthquakes are troublesome to foretell and can’t be prevented. Nonetheless, we will mitigate their affect. Via built-in research of the area’s geology, geophysics and geodesy we will discover out the place there are energetic earthquake faults. We are able to additionally estimate how highly effective the earthquakes on these faults may very well be and the way typically they could occur once more. This helps us perceive how sturdy future earthquakes in a particular space may very well be. Faults that don’t have earthquakes typically however can nonetheless produce sturdy ones are a giant concern. Sooner or later, discovering and finding out these kind of faults might be a spotlight of earthquake analysis.
One of the simplest ways to minimise earthquake harm is to enhance seismic constructing design codes to face up to the very best potential seismic exercise. This can assist buildings and different buildings maintain up higher in opposition to sturdy shaking. As well as, it’s essential that conventional houses and rock constructions in mountain villages be strengthened to stop future disasters. New constructions should be examined and designed cheaply and effectively, respecting new seismic constructing requirements.
