How mud-brick housing made the Morocco earthquake so deadly

Almost a week after the most powerful earthquake to strike inside its borders since at least 1900, Morocco is still counting the dead. Officials reported at least 2,946 people had died while more 5,674 were injured in the 6.8 magnitude quake, which struck late the evening of Sept. 8 in a remote region of the High Atlas mountains.

The death toll makes the quake the deadliest in the country since 1960, and rescuers and experts warned the severe damage and loss of life was exacerbated by the vulnerability of the traditional mud, brick and stone-built housing in the region.

“It’s difficult to pull people out alive because most of the walls and ceilings turned to earthen rubble when they fell, burying whoever was inside,” a military rescue worker, asking not to be named because of army rules against speaking to media, said at an army centre south of the historic city of Marrakech not far from the quake epicentre.

An ancient construction technique

Homes in the villages dotted across the High Atlas mountains and foothills where the quake’s shaking was most severe are often constructed from stone, wood and raw earth using techniques that are centuries old. They are often built by the families who live in them, without any architect’s help and with extensions tacked on to the main structure over time.

These traditional construction techniques are often praised for their ability to help regulate heat in the hot weather conditions of the region. A National Geographic article published this year said local architects preferred mud brick based construction over concrete because they “create cooler structures than concrete, are cheaper, and require less energy to produce.”

Local architects also champion the techniques for preserving regional culture and making use of hundreds of years of architectural expertise tailored to the local climate and geography.

Within the hard-to-access villages of the High Atlas mountains, which can rely on networks of rough dirt roads to connect them, these techniques also allow homes to be constructed primarily from locally-sourced materials where more modern building materials are difficult to get in.

With poverty levels high in the region, cost is often a driving factor, too.

But the benefits of the earthen materials used to address local climate and economic conditions are also uniquely vulnerable to earthquakes.

An illustration of how mud bricks are made and used to construct houses and villages.

A man makes mud bricks. The mud is mixed with water, straw and sometimes manure to make the bricks in a mould. The mud bricks are left to dry on the ground for days.

The bricks are then used to create a house. The walls are built from mud bricks. The home has a stone base and small windows. A mud roof rests on a structure of wood and reed canes. Entire families sleep in the same room.

Finally, an illustration of the town of Anebdour, Morocco, which is made up of layers of such mud brick built houses and structures along a hillside.

September quake

Last week’s earthquake struck in the High Atlas Mountains of western Morocco shortly after 11 p.m. on Sept. 8. Strong shaking was felt in the nearby city of Marrakech, a UNESCO World Heritage site, but the worst damage was found in the foothills outside the city and in the more remote mountain villages.

“The level of destruction is … absolute,” Antonio Nogales, head of Spain’s United Firefighters Without Borders NGO said, speaking from Amizmiz, south of Marrakech, which was hard hit by the earthquake.

A map showing the shake intensity of the quake. The intensity is measured from severe to very light shaking and radiates out irregularly from the epicentre of the quake. The most severe shaking was measured in the High Atlas mountains.

The force of the shaking that earthquakes produce can result in dramatically different damage to housing and other structures depending on how they were constructed. Where earthquake-resistant structures using materials like reinforced concrete may only sustain moderate damage, more vulnerable structures — like the mud-brick houses typical in the High Atlas — can suffer much more severe destruction.

Two maps showing the potential damage to two different types of buildings, those which are built to resist earthquakes and those vulnerable to them, like mud brick buildings. The map shows that areas that receive the same shaking force will more severely damage vulnerable buildings.

Large, deadly earthquakes are not especially common in Morocco and even rarer in the High Atlas mountain region. The 6.8 magnitude quake was the largest within Morocco in 120 years.

The deadliest quake in Morocco’s recent history was a 5.9-magnitude earthquake that struck the western coastal town Agadir in 1960 and led to over 13,000 casualties. More recently, in February 2004, a 6.4-magnitude earthquake killed about 628 people in northern Morocco.

“Morocco is not the first place that comes to mind when people think of earthquakes, but they do happen,” said Bill McGuire, professor emeritus of Geophysical & Climate Hazards at UCL. “The problem is that where destructive earthquakes are rare, buildings are simply not constructed robustly enough to cope with strong ground shaking, so many collapse resulting in high casualties.”

A map of all earthquakes since 1900 to hit near Morocco. The majority of the earthquakes are located in the north of the country and along the tectonic plate boundary between Africa and Europe. Earthquakes in the High Atlas mountain region of Morocco are significantly more rare.

Earthquakes of magnitude 5 and above inside Morocco since 1900

Little hope for rescuers to find survivors under the brick debris

“The problem with rubble and mud brick materials for the older houses, the whole material is so brittle,” said Colin Taylor, an emeritus professor of earthquake engineering at the University of Bristol. “You’ve basically got a pile of rocks and mud dust and that just congeals together.”

An illustration of a mud brick built house and how it can be damaged during an earthquake. The earthquake causes violent lateral shaking. The mud walls of the house cannot withstand the shaking and collapse.

When reinforced concrete structures collapse after an earthquake, the material can still leave voids with enough air and space to allow people trapped to survive, sometimes for days after the quake. In earthen material construction, the material fails without leaving those gaps.

“It really won’t leave many pockets that you could survive in, any air pockets that you could breathe through. You’re being buried underground, if you like, by all this material falling around you, sort of packing itself around you,” said Taylor.

An illustration of a collapsed mud brick house. Brick dust suspended in the air considerably limits breathing. Heavy bricks and other materials leave no voids in the rubble. Modern houses with sturdy structures can leave “life voids”, which can hold out hope of finding survivors after several days.

Villages in ruins

Initial estimates of the damage by the United Nations Satellite Centre (UNOSAT) showed destruction in several towns and villages near the epicentre. Some were nearly completely destroyed.

According to UNOSAT, about 5 million people were exposed to moderate to severe shaking during the earthquake.

Map showing the damage caused by the earthquake in the villages closer to the epicentre, where the impact has been severe.

Satellite images showing the destruction to structures in several villages in Morocco’s High Atlas mountain region.

Villagers in some of the most isolated areas hit by Morocco’s earthquake were still living in makeshift tents and relying on donkeys to bring vital supplies as they waited for state aid to reach them nearly a week after the disaster.

While orderly camps of large, government-issued tents and military field hospitals have sprung up in some of the larger towns, parts of the rugged region are still surviving on donations left on roadsides by citizens.

Jon McClure, Edmund Blair

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