A army helicopter delivers help in the aftermath of a lethal earthquake in Talat N’Yaaqoub, in Morocco September 12, 2023.
| Photo Credit: Reuters
The epicentre of Morocco’s devastating earthquake on 8 September was in the High Atlas Mountains, about 71km south-west of Marrakesh. Moina Spooner, from The Conversation Africa, requested Jesús Galindo-Zaldivar, who has been finishing up analysis on the formation of the Atlas mountains and the geology of the space, about the components which led to this example.
What analysis have you ever been doing in Morocco’s Atlas Mountains?
The Atlas Mountains are a captivating vary in north-west Africa, spanning Morocco, Algeria and Tunisia. They’re located south of the most important Eurasia and Africa (Nubia) tectonic plate boundary.
This space doesn’t normally have loads of earthquakes in comparison with different locations close to the edges of tectonic plates, the place the actions of plates will trigger intense seismic exercise. But in 1960 the Agadir earthquake caused loads of harm and lack of life.
I’m a part of a crew of geologists, geophysicists and geodesists from varied Moroccan universities and Spanish establishments finishing up analysis in the space. We need to perceive this mountain vary’s growth and its place at the fringe of a continental plate boundary. Studies of seismic exercise, gravity and different geophysical phenomena enable us to know the Earth’s deep construction, all the way down to depths exceeding 100km.
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Through area geological analysis, we are able to detect and analyse faults – fractures or cracks in the Earth’s crust alongside which there was motion. These actions could be horizontal, vertical or diagonal, they usually happen as a consequence of the immense forces appearing on the Earth’s tectonic plates.
Finally, utilizing geodetic strategies (GPS recordings) we’re capable of decide how tectonic plates are shifting. This is completed by repeatedly 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 is 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 counsel that there was current motion in 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 price of about 1 millimetre annually. This occurs as a result of the Eurasian and African plates are shifting nearer to one another. This squeezing motion is liable for creating the tallest mountains in the space, the southern fringe of the place these two large plates meet.
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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. According to estimates by Morocco’s National 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 accrued stress, which is attribute of a seismic fault.
The 6.8 magnitude implies that the fault liable for this earthquake might be round 30km lengthy. This estimate takes into consideration the relationships between energetic fault size and earthquake magnitudes.
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So, why don’t we see many earthquakes on this space, regardless that it’s a spot the place the tectonic blocks are shifting and the mountains are rising? Earthquakes occur when there’s a sudden shift in rocks alongside a fault line, caused by the launch of saved power that’s been increase over time. In 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 bought an excessive amount of for the fault to deal with, it caused an earthquake.
In this mountain belt faults won’t produce earthquakes fairly often. After the earthquake, the rocks in the space moved and adjusted, however different close by faults would possibly now be underneath additional stress, they usually might produce smaller earthquakes often called aftershocks that may proceed for months and even years.
What ought to authorities be doing to organize?
Earthquakes are tough to foretell and can’t be averted. However, we are able to mitigate their affect. Through built-in research of the area’s geology, geophysics and geodesy we are able to discover out the place there are energetic earthquake faults. We may estimate how highly effective the earthquakes on these faults might be and the way usually they could occur once more. This helps us perceive how robust future earthquakes in a particular space might be. Faults that don’t have earthquakes usually however can nonetheless produce robust ones are an enormous concern. In the future, discovering and studying these kind of faults will likely be a spotlight of earthquake analysis.
The greatest method to minimise earthquake harm is to enhance seismic constructing design codes to face up to the highest attainable seismic exercise. This will assist buildings and different buildings maintain up higher in opposition to robust shaking. In addition, it’s essential that conventional houses and rock constructions in mountain villages be bolstered to stop future disasters. New constructions have to be examined and designed cheaply and effectively, respecting new seismic constructing requirements.
Jesús Galindo-Zaldivar, Professor of Geodynamics, Universidad de Granada
This article is republished from The Conversation underneath a Creative Commons license. Read the authentic article.
