GS Paper 1
Syllabus: Geography: Geomorphology
Context: A powerful earthquake with a magnitude of 6.8 struck Morocco, causing extensive damage and a death toll exceeding 2,400 people. The earthquake’s epicentre was in the Atlas Mountains near Marrakech.
Reason for the Earthquake:
The earthquake in Morocco resulted from a geological phenomenon known as a “reverse fault.”
- Tectonic Plate Interaction: Morocco is situated in an area where the Eurasian and African tectonic plates converge.
- Plate Boundary Activity: The Atlas Mountains, where the earthquake occurred, are actively rising due to the convergence of these two large tectonic plates
- Seismic Stress Accumulation: Although the region had not experienced major recorded earthquakes before, stress had been accumulating underground for an extended period due to the slow movement of tectonic plates.
- Oblique-Reverse Fault: This type of faulting is common in areas of compression along the convergent plate boundaries. The stress along these fault lines can induce earthquakes as rocks abruptly shift to release accumulated stress.
More about Oblique-Reverse Fault:
An oblique-reverse fault is a geological fault characterized by both horizontal and vertical movements along the fault plane. In this type of fault, rocks on one side of the fault plane move vertically upward while also sliding horizontally in a lateral direction. This movement occurs due to the compression of tectonic plates, where one plate is converging into another.
Various types of faults:
|Type of Fault||Description|
|Dip-Slip Faults||Movement along the direction of the dip plane.|
|Vertical movement either up (reverse dip-slip) or down (normal dip-slip) along the fault plane.|
|Common in regions experiencing crustal compression or extension.|
|Examples: Reverse faults (upthrown block above the fault plane) and Normal faults (downthrown block above the fault plane).|
|Strike-Slip Faults||Horizontal movement along the fault plane.|
|Movement is parallel to the strike of the fault.|
|Common in transform plate boundaries where tectonic plates slide past each other horizontally.|
|Oblique-Slip Faults||Show characteristics of both dip-slip and strike-slip faults.|
|Movement occurs in two directions: horizontal (strike-slip) and vertical (dip-slip) along the fault plane.|
Why the earthquake in Morocco has caused so much damage?
|Epicentre Location||The earthquake’s epicentre was in the High Atlas Mountains (close to the city of Marrakesh), causing it to affect populated areas and infrastructure.|
|Depth||The depth of the earthquake, estimated between 8km and 26km, was relatively shallow, making it more dangerous as shallow earthquakes transmit more energy to the surface.|
|Previous Earthquake Activity||The region had not experienced major recorded earthquakes before, suggesting that stress had been accumulating underground for an extended period before being released in this earthquake.|
|Lack of Preparedness||Earthquakes are relatively rare in North Africa, so Morocco was not well-prepared for such a calamity. Many buildings, especially in rural areas and older cities, were not constructed to withstand strong tremors.|
The Western Himalayas in India are considered one of the most dangerous seismic zones globally, and the entire Himalayan region, spanning from the Hindu Kush mountains to Arunachal Pradesh, is at risk of a major earthquake with a magnitude exceeding 8 on the Richter scale. This heightened risk is attributed to the substantial energy accumulation along faultlines due to the ongoing interaction of various tectonic plates.
However, earthquakes cannot be accurately predicted because there is currently no equipment or method to detect precursory signals within the Earth that would indicate an impending major earthquake. Such signals would need to be specific to significant seismic events and not indicative of minor movements in the Earth’s crust.
Why are the world’s fold mountain systems located along the margins of continents? Bring out the association between the global distribution of Fold Mountains and the earthquakes and volcanoes. (UPSC 2014)