On the fateful night of September 8, a rare and powerful earthquake rocked Morocco, claiming the lives of hundreds and causing extensive damage, including to the UNESCO World Heritage Site, Marrakech.
What is an Earthquake?
An earthquake is a profound shaking of the Earth’s surface caused by the movement beneath the Earth’s crust. The point beneath the Earth’s surface where the earthquake originates is referred to as the hypocenter, while the point directly above it on the Earth’s surface is known as the epicenter. Earthquakes occur when tectonic plates, the massive blocks of the Earth’s crust, suddenly slide past each other, releasing stored-up elastic strain energy in the form of seismic waves. These waves propagate through the Earth, resulting in ground tremors. Earthquakes are assessed using various scales, including the Moment Magnitude Scale (Mw) for measuring the earthquake’s total moment release and the Richter scale for determining its energy released. Additionally, the Mercalli scale assesses visible damage caused by an earthquake.
Earthquake in Morocco: Epicenter and Magnitude
The epicenter of this destructive earthquake was situated in the High Atlas Mountain range, approximately 72 kilometers from Marrakech. The earthquake registered a magnitude of 6.8 on the Richter scale, categorizing it as a “strong” quake. It also occurred at a relatively shallow depth below the Earth’s surface, enhancing its destructive potential. According to the US Geological Survey (USGS), the focal point was 18.5 kilometers beneath the surface, while Morocco’s own seismic agency estimated it at 11 kilometers. Regardless of the precise depth, shallow earthquakes like this one tend to be more destructive as they transfer more energy to the surface compared to deeper-seated earthquakes.
Regional Earthquake Occurrence
Earthquakes of this size are infrequent in the region, although not entirely unexpected. The US Geological Survey reported nine earthquakes with a magnitude of 5 or higher in this area since 1900, with none exceeding a magnitude of 6.
Reason behind Morocco’s Earthquake
- Geological Background: While seismic activity is relatively low in this region, Morocco has seen its share of large and destructive earthquakes, particularly in the western Mediterranean. These earthquakes are a result of the northward convergence of the African plate and the Eurasian plate along a complex plate boundary.
- Oblique-Reverse Faulting: The USGS attributes Morocco’s earthquake to oblique-reverse faulting at shallow depths within the Moroccan High Atlas Mountain range.
Types of Faults
Faults are fractures or zones of fractures between two blocks of rock. Faults allow these blocks to move relative to each other, potentially causing earthquakes if the movement is rapid. Scientists classify faults based on the angle of the fault with respect to the Earth’s surface (dip) and the direction of the slip along the fault.
Oblique-Reverse Faulting
Oblique-reverse faulting, also known as oblique-thrust faulting, is a geological faulting type where rocks on one side of the fault plane move both vertically and horizontally in response to compressional forces. This type of faulting is common in areas where one tectonic plate converges into another.
Impact and Aftermath
The earthquake’s impact has been devastating, with more than 2,000 lives lost, mainly in Marrakech and the five provinces near the epicenter. Buildings, including historical landmarks, have suffered severe damage, raising concerns about the restoration of the UNESCO World Heritage Site in Marrakech.
UPSC Mains Questions
- What factors make shallow earthquakes like the one in Morocco more destructive compared to deeper ones, and how does this impact the affected region?
- How do geological fault types, such as oblique-reverse faulting, contribute to seismic activity, and why is it important to understand these fault mechanisms in earthquake-prone regions?
- What measures can Morocco and other earthquake-prone regions take to mitigate the devastating impact of earthquakes on human lives and historical heritage sites like Marrakech?
- Considering the geological forces at play in the region, what are the prospects for future earthquakes in Morocco, and how can residents and authorities prepare for such events?