Earth quake in Morocco

A rare, powerful earthquake struck Morocco recently, killing hundreds of people and damaging buildings, including in the historic city of Marrakesh.

North: Spain (with water border through the Strait of Gibraltar) and small Spanish-controlled exclaves, including Ceuta, Melilla, and Peñón de Vélez de la Gomera.
East: Algeria.
South: Western Sahara.
De facto southern boundary with Mauritania due to Morocco’s control over most of Western Sahara.

Earthquakes are infrequent in North Africa, and seismicity rates are relatively low.
Marrakesh, including the historic old city (UNESCO World Heritage Site), experienced building collapses and structural damage.

Magnitude of the earthquake: 6.8
Followed by an aftershock of magnitude 4.9 just 19 minutes later.
Epicentre located in the town of Ighil, approximately 70 km southwest of Marrakech.
Epicentre depth: 18.5 km (shallow earthquake).
Shallow earthquakes are more dangerous as they carry more energy than deeper ones.
Deeper earthquakes spread seismic waves farther but lose energy while traveling greater distances.

While seismicity rates are indeed lower in the region, making earthquakes rarer, they are not completely unheard of.
According to the US Geological Survey (USGS), large destructive earthquakes have been recorded and reported from Morocco in the western Mediterranean.
- Such quakes occur due to the “northward convergence of the African plate with respect to the Eurasian plate along a complex plate boundary.”
With respect to current quake, the USGS attributed it to “oblique-reverse faulting at shallow depth within the Moroccan High Atlas Mountain range”.
The Atlas Mountains span about 2,300 kilometres across Morocco, Algeria and Tunisia.
- Known as fold mountains, they were created by the collision of tectonic masses: the Eurasian Plate to the north and the African Plate to the south.

A fault is a fracture or zone of fractures between two blocks of rock.
- Faults allow the blocks to move relative to each other, causing earthquakes if the movement occurs rapidly.
- During a quake, the rock on one side of the fault suddenly slips with respect to the other.
Scientists use the angle of the fault with respect to the surface (known as the dip) and the direction of the slip along the fault to classify faults.
- Faults which move along the direction of the dip plane are dip-slip faults, whereas faults which move horizontally are known as strike-slip faults.
Oblique-slip faults show characteristics of both dip-slip and strike-slip faults.
The term ‘reverse’ refers to a situation that the upper block, above the fault plane, moves up and over the lower block. This type of faulting is common in areas of compression — when one tectonic plate is converging into another.

AMIGOS IAS