Afghanistan earthquake: What makes South Asia a ‘hotbed’ of rigorous seismic activity

An earthquake measuring 7.5 on the Richter scale hit the Hindu Kush region of Afghanistan on Monday. The tremors were also felt in the northern Pakistan and adjacent parts of India and Afghanistan.

According to the U.S. Geological Survey (USGS), the earthquake occurred “as the result of reverse faulting at intermediate depths, approximately 210 km below the Hindu Kush Range in northeastern Afghanistan.” The “intermediate-depth” earthquake had an approximate focal depth of 210 km.

The earthquake that hit Afghanistan was just one of the many that have been felt across the region in the past. However, three of them have been particularly devastating in the past – in 2001, 2005 and the most recent one that hit Nepal in April, 2015. It is estimated that the three quakes killed nearly 120,000 people.

The history of the violent seismic activity in the region can be attributed to the movement of the southern Indian Plate against the Eurasia Plate in the north. Each year, the Indian subcontinent moves northward and converges with the Eurasian plate at a velocity of about 37 mm.

India was initially a large island situated off the Australian coast. A vast ocean separated it from the Asian subcontinent. When prehistoric supercontinent called Pangea broke apart nearly 200 million years ago, India started to drift towards the north. The movement led to a collision between the Indian and the Eurasian plate, a phenomenon known to have created the Himalayan, the Hindu Kush, the Kakoram and the Pamir ranges.

The USGS says that the collision still takes place and results in an increase of 0.4 inches in the height of the Himalayas each year. The continuous movement makes the South Asian subcontinent a “hotbed” of violent seismic activity.

“It's a really intricate area. This is where several plates have met, over several millions of years, and formed this really complex deformation pattern,” said Professor Martin Mai of the King Abdullah University of Science and Technology in Saudi Arabia, in an interview with the BBC.

"Many fault lines have been mapped, and not all of them are active right now. But any of them could become active at any time, through such an earthquake," he added.

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