Another catastrophic earthquake ripped through Afghanistan in the early hours of Wednesday, claiming nearly 1,000 lives and injuring scores more. The earthquake measured 6.1 magnitude on the Richter scale and the epicenter was at a depth of 10 km. The quake destroyed tons and tons of crucial infrastructure in the country which is already undergoing political and economic turmoil.
In the midst of death and destruction, the thought lingers in our heads – why did this happen?
Geography of the Hindu Kush
In order to answer this question, it is pertinent that we examine the geography of Afghanistan and its neighboring countries. If this news sounds familiar, you’re right!
Afghanistan, Pakistan, Tajikistan, Jammu and Kashmir and Ladakh often make headlines for earthquake related reasons as these places are in and around the Hindu Kush area – one of the most earthquake-prone regions on Earth. The slow collisions between the Indian subcontinent and the Eurasian tectonic plate are believed to cause the extremely frequent earthquakes in this region. In fact, this month alone, this region has witnessed over 35 minor earthquakes so far in just 22 days.
While the Himalayan region of the Hindu Kush might not seem as ominous as the Pacific “Ring of Fire” – another region of terrific seismic activity on our planet – it certainly doesn’t lack the punches. The United States Geological Survey (USGS) has called the Hindu Kush region “one of the most seismically hazardous regions”, with one of the highest rates of deep earthquakes in the world .
Since May 9, the region has recorded more than 100 earthquakes, according to the National Seismology Center. Afghanistan, in particular, has experienced 36 such earthquakes. However, only six times the magnitude of these tremors was 5 or greater.
But first, let’s look at why earthquakes happen in the first place.
Some of us may be familiar with the term “tectonic plates”. These are large, thin plates that make up the Earth’s crust and upper mantle (commonly called the “lithosphere”) that are constantly in motion. The Earth has about seven or eight main plates that move under each other, inside each other or away from each other. The movie “Ice Age 4: Continental Drift” actually showed a crude version of this phenomenon!
These different movements cause interesting physical features, such as the Himalayan mountain range (which still increases by about a centimeter in height every year) and the Mariana Trench, which formed as the mighty Pacific plate subducted under the smaller and less dense Philippine Plate. .
The hard edges of some plates can sometimes lock them in place as they constantly move and rub against each other. But because the plates are still moving despite locking, pressure builds up on them over time – imagine a strong elastic band that’s tied at one end and gradually pulled apart at the other.
Once there is too much pent up stress, he releases it with a furious jolt, sending powerful seismic waves of energy out of the rift and shaking the entire area! This can have devastating consequences if the center of activity is close to the surface.
Therefore, since it is inevitable that these plates will get stuck on top of each other, smaller earthquakes are actually a good sign, as it means the plates are not accumulating large amounts of seismic energy that could trigger large shocks and aftershocks in the region.
Curious case from the Hindu Kush region
The Hindu Kush region includes an area that experiences constant seismic activity as the Indian tectonic plate continually gets stuck in the Eurasian plates. The fault line that circumvents the Hindu Kush region is the same as that which supports the Himalayas.
One of the largest earthquakes in the region (magnitude 7.6) occurred in October 2005, killing 87,000 people and displacing millions. After that we had the April 2015 tremors (magnitude 7.8-8.1) in Nepal which ended up causing an avalanche which killed nearly 9,000 people.
Although the Hindu Kush mountain range experiences a significant number of earthquakes each year, it does not lie directly on the fault line, which puzzles scientists. In fact, it’s several miles from the idle crash zone where the Eurasian and Indian tectonic plates regularly collide. So how do we explain these earthquakes?
A 2019 study published in the journalTectonic proposed the existence of a “long blob” of rock that gradually drains from the belly of the range and into the hot, viscous mantle below. This could cause the 150 km deep mountain blob to move away from the crust at a rate of 10 centimeters per year, causing the resulting stress to produce earthquakes in the region.
This downward movement is actually 10 times faster than the tectonic movement between the Indian and Eurasian plates – which is a major driver of most earthquakes in the region!
Although the actual reason may remain unclear, it is clear that greater caution should be taken in places close to the Hindu Kush region, many of which are close to Indian states.
While almost all Himalayan states are at constant risk, the maximum risk areas for high intensity earthquakes are classified as Zone-V in India. The entire region of northeastern India, as well as parts of Jammu and Kashmir, Himachal Pradesh, Uttarakhand, the Rann of Kutch in Gujarat, northern Bihar and the Andaman Islands and Nicobar are included in the area.
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