Earthquake in Morocco
On 8 September 2023 at 23:11 DST (22:11 UTC), an earthquake with a moment magnitude of 6.9 and maximum Mercalli intensity of IX ("Violent") struck Morocco's Al Haouz Province. The earthquake's epicenter was southwest of Marrakesh, near the town of Ighil and the Oukaïmeden ski resort in the Atlas Mountains. It occurred as a result of shallow oblique-thrust faulting beneath the mountain range. At least 2,960 deaths were reported, with most occurring outside Marrakesh. Damage was widespread, and historic landmarks in Marrakesh were destroyed. The earthquake was also felt in Spain, Portugal, and Algeria.
It is the strongest instrumentally recorded earthquake in Morocco, the deadliest in the country since the 1960 Agadir earthquake, and the second-deadliest earthquake of 2023 after the Turkey–Syria earthquakes. Its magnitude also makes it the largest earthquake on the African continent since the 2006 7.0 Mozambique earthquake and the largest in North Africa since the 1980 7.1 El Asnam earthquake. Over 2.8 million people from Marrakesh and areas surrounding the Atlas Mountains were affected, including 100,000 children. Following the earthquake, many countries offered humanitarian assistance, and Morocco announced a three-day period of national mourning.
Tectonic setting.
Morocco lies south of a major tectonic boundary between the African plate and the Eurasian plate. This major fault stretches from the Azores to Gibraltar Strait where it is doinated by right-latera strike-slip movement. In the Gibraltar Arc and Alboran Sea, at the eastern end of the fault it becomes transpressional with the development of large thrust faults. East of the Strait of Gibraltar, in the Alboran Sea, the boundary becomes collisional in type. Most of the seismicity in Morocco is related to movement on that plate boundary, with the greatest seismic hazard in the north of the country close to the boundary. In 2004, the coastal province of Al Hoceima was struck by a magnitude 6.3 earthquake that left 628 people dead and 926 injured. In nearby Algeria, magnitude 7.3 earthquake occurred in 1980 that killed 2,500 people.
The Atlas Mountains are an intracontinental mountain belt that extends from Morocco to Tunisia. These mountains formed from a collision during the Cenozoic. The mountain range reaches its highest elevation to the west, in Morocco. The High Atlas, a subrange, formed when an ancient Triassic rift was reactivated. However rather than resuming the rifting process, the reactivation compressed the rift due to the collision in the north. Due to the unusually high topography of the Atlas range, mantle upwelling may have played a role in its orogeny. The crust beneath the Atlas range from , considered thin and physically impossibe to support high elevations exceeding . Typically, a crustal thickness of is required, hence mantle upwelling raises the overlying crust.
The seismicity of Morocco is concentrated in its northern region and the Alboran Sea. South of the Rif, seismic activity is sparse but widely distributed across the Middle Atlas, High Atlas, and Anti-Atlas. Seismicity in the Saharan Atlas is limited, and is absent in the Saharan region south of the belt; it is also less active eastwards in Algeria and Tunisia. Previously, the largest earthquake recorded in the Atlas Mountains was a 5.9 earthquake that struck Agadir in 1960. Earthquakes in the Atlas Mountains display focal mechanisms of strike-slip, thrust or a combination of both (oblique-slip).
Earthquake.
Measuring 6.9 at a depth of , it is the strongest earthquake recorded by a seismograph with an epicenter in Morocco. Morocco's seismic agency reported a of 7.2 and focal depth of . The tremors were detected by monitoring stations as far away as Egypt.
Mechanism.
The earthquake had a focal mechanism indicating oblique-thrust faulting beneath the High Atlas. The rupture occurred on a steep-dipping oblique-reverse fault striking northwest or a shallow-dipping oblique-reverse fault striking east. The USGS estimated the fault rupture area to be by on an east-northeast striking, north–northwest dipping fault. Slip was generally observed at to depth, but mostly concentrated around the hypocentre within an elliptical slip patch long by wide. A maximum displacement of was observed at depth while there was little to no slip above depth. Many east-west and northeast–southwest strike-slip and thrust faults occur in the High Atlas. Since 1900, there has not been a 6.0 or larger earthquake within of the recent earthquake's epicenter; but nine 5.0 and larger events have occurred to its east. In another finite fault model published by Italy's National Institute of Geophysics and Volcanology, the focal depth was determined at beneath the High Atlas. The focal mechanism of this model displayed reverse and left-lateral faulting. Slip occurred in an elliptical area along an east-northeast–west-southwest trending fault dipping 69° north–northwest. A peak slip of occurred at .
Geodetic modeling suggests the earthquake originated from within the lower crust and ruptured up to the middle crust. The deeper depth and greater remoteness from populated areas compared to the earthquake that struck Agadir in 1960 meant it caused fewer casualties and damage. The range of depth where slip occurred is unusually deep for crustal earthquakes as they tend to occurr shallower than depth. Fluid and magma associated with the mantle plume beneath the High Atlas may have intruded via a fault and pervade across, bringing it closer to rupture.
No surface faulting occurred hence the causative fault responsible could not be identified, however the focal mechanism suggests rupture on a steep north-dipping plane or shallow south-dipping plane. The USGS finite fault is aligned with the former solution. Two dominant shallow-dipping thrust systems, the North and South Atlas faults, occur in the western High Atlas. Their fault geometries contradict that of the USGS finite fault's preferred steep-dipping plane. Other unmapped faults within the range, including the Tizi n'Test Fault, have surface projections that match closer to the USGS finite fault. If the rupture occurred on the shallow south-dipping plane, a possible source is a low-angle detachment beneath the High Atlas. Geologists have previously interpreted low-angle faults in the region in past studies. For the steep north-dipping plane, the possible source are unmapped or blind thrust faults. The Tizi n'Test Fault, a north-dipping fault where no recent activity has been recorded, may be a possible source of the earthquake. Cornell University geologist Judith Hubbard said the fault was active 300 million years ago during the formation of Pangaea and later, its fragmentation. Ancient faults, such as the Tizi n'Test Fault, create zones of strain within the crust and could reactivate, such as the case in Morocco.
Ground effects.
Vertical movement of the land surface detected by repeat observations of the Sentinel-1 satellite is consistent with movement on a blind thrust fault dipping north. An analysis of satellite data obtained from Daichi-2 by the Geospatial Information Authority of Japan revealed a surface uplift around the epicenter and of subsidence to the south. Surface deformation was observed around the epicenter across a area trending east–west, and trending north–south.
According to the United States Geological Survey's PAGER service, the earthquake had a maximum Modified Mercalli intensity of IX ("Violent"). Intensity VIII ("Severe") shaking was felt by approximately 157,000 residents, including the town of Azgour and villages surrounding the Atlas Mountains. Intensity VII ("Very Strong") shaking was felt by over 811,000 people, with intensity VI ("Strong") shaking felt by 3.2 million residents, including in the cities of Marrakesh, Taroudant and Ouarzazate. Shaking of intensity V ("Moderate") was felt in Agadir, Beni Mellal, and Safi, with intensity IV ("Light") shaking being felt in Casablanca. According to the European-Mediterranean Seismological Centre, it was also felt in Portugal, Spain, Mauritania, Algeria, Western Sahara and along the coast of the Strait of Gibraltar.
Damage and casualties.
At least 2,960 people died and 5,674 were injured; including over 2,500 other who were seriously injured. Many fatalities occurred in remote locations south of Marrakesh. In Al-Haouz and Taroudant provinces, the death toll stood at 1,684 and 980, respectively. Forty-one people died in Ouarzazate; 400 in Taroudant; 202 in Chichaoua; 100 in Douzrou; 40 in Moulay Brahim; 30 in Ouirgane; 15 in Tinmel; 36 in Anerni; 22 in Tinzart; and 18 died in Marrakesh. Deaths also occurred in Casablanca, Agadir and Youssoufia. Four French and a British national were among the fatalities. Fifteen French nationals and some Americans were injured. At least 40,759 houses and 2,930 villages were damaged; 19,095 additional houses collapsed. At least 585 schools were damaged, seven teachers died and 39 others were injured. More than 18,000 families were affected in Al-Haouz alone. One person was injured by rockfalls in Imi N'Tala following an aftershock on 13 September.
The earthquake caused $7 billion in damage; the direct economic loss of $308 million represented 0.24 of the nation's GDP. The majority of damage occurred in Marrakesh and five provinces around the epicenter. Near the epicenter, at Amizmiz, damage was reported throughout, and rescuers used their hands to sort through debris. Nearly all of the 50 traditional houses in the village of Majat were destroyed and dozens of people died. Ninety-percent of houses in Asni were destroyed, while in Essaouira, building's facades toppled.
Some homes in the older districts of Marrakesh and parts of the city walls collapsed; at Jemaa el-Fnaa, a minaret of the Kharboush Mosque and parts of its walls collapsed onto vehicles. Damage also occurred at the Kutubiyya Mosque while several historic buildings in the Medina of Marrakesh also collapsed. A tower of the Tinmel Mosque partially collapsed and the surrounding walls fell.
The towns of Tafeghaghte, Adassil and Imlil, and nearby villages surrounding Mount Toubkal were destroyed or severely damaged. An estimated 200 homes were destroyed in Ijoukak and between 80 and 100 residents, around half of its population, were killed. In Tafeghaghte, a village of 200 residents, 90 died and many remained missing. The village of Ighil, near the epicenter, was also severely damaged, however only one injury occurred, as nearly all of the village's residents were attending an outdoor wedding at the time of the earthquake. In Adassil, 32 students from the same school were killed. Outside Agadir, in the villages of Taqi and Tadrart, many homes were destroyed. At least 70 people died in the village of Imi N'Tala. In the city of Taroudant, several old or historic districts were badly damaged. The condition in Tinzart was described as "one giant pile of rubble".
Search and rescue.
People in Marrakesh removed rubble by hand while awaiting heavy equipment. Many residents remained outdoors for fear of another earthquake. Posts on social media showed people evacuating a shopping centre, restaurants and apartment buildings. Residents of the city spent the first three nights outdoors; filling up roundabouts, car parks and a public square. Some businesses in the city reopened on 10 September as King Mohammed VI recommended commercial operations to continue. Unsafe portions of the city were sealed off by officials while tourists and locals continued to move about. In the capital, Rabat, north of the epicenter, and at Imsouane, a coastal town, residents left their homes.
The General Secretary of the Directorate General of Internal Affairs said officials and security teams assembled resources to supply aid and assess damage. The Moroccan army cleared one of the main roads to the worst-affected areas, allowing vital assistance to reach people. In Salé, trucks carried blankets, camp beds and lighting devices to the affected areas. Semi-trailers also carried supplies to reach these areas. Local channel 2M shared videos of emergency vehicles travelling along a dirt road. Rescue missions were disrupted as the roads through the mountainous region were congested with vehicles and fallen rocks. Collapsed buildings made from traditional mud brick, stone and rough wood complicated lowered the chances of survival as these materials disintegrated and amalgamated. The amalgamated rubble left limited air pockets for those trapped. In Al-Haouz Province, rocks were removed from roads to enable ambulances and aid to reach the affected areas. A highway in the Atlas Mountains, congested with ambulances, taxis and Red Cross members, was used to treat the injured; the severely wounded were transported to a hospital in Marrakesh. In remote areas that were difficult to access, the Royal Moroccan Armed Forces used helicopters to supply basic needs. The Moroccan Health Ministry mobilized more than 2,000 doctors and nurses to respond to the earthquake.
There was a surge in wounded people admitted to hospitals in Marrakesh. Injured people from outside Marrakesh also began to trickle into the city to get treatment. An appeal was made to the city's residents for blood donations. On the morning of 9 September,