Why Afghanistan’s Complex Tectonics Make It Earthquake-Prone

Afghanistan Earthquakes: Why The Region is Prone to Frequent Seismic Activity

• Context: Recent earthquakes in Afghanistan that caused widespread destruction.

A powerful earthquake of magnitude 6.3 struck western Afghanistan on October 15, causing further destruction just days after previous earthquakes took the lives of over 1,000 people. The recent earthquakes centered in the Herat province have left trails of devastation across villages and communities. According to the United Nations, the death toll has climbed to well over 2,000 people. Over 1,700 houses and 15 settlements have been flattened by the intensive tectonic activity in the region.

Afghanistan frequently faces earthquakes that cause widespread damage. In June 2022, an earthquake of magnitude 6.1 hit the Khost and Paktika provinces, resulting in over 1,000 fatalities. In 2015, a major earthquake in the northeast led to the deaths of over 200 people in Afghanistan and northern Pakistan. Going further back in history, a 6.1-magnitude earthquake in 2002 killed around 1,000 people in northern Afghanistan. In 1998, another powerful earthquake and subsequent aftershocks in the northeast claimed at least 4,500 lives.

The recent spate of earthquakes has struck Afghanistan at a time when it is already reeling under a humanitarian crisis. Millions of Afghans are struggling with rising poverty and hunger. The United Nations has warned that the earthquakes have further exacerbated the suffering, as essential services have been disrupted. With thousands displaced and infrastructure damaged, rescue and rehabilitation efforts face massive obstacles. As the region deals with the aftermath, understanding why earthquakes frequently shake Afghanistan is critical.

Overview

Tectonic Setting of Afghanistan

Geography and Plate Boundaries

• Located on Eurasian Plate, surrounded by Arabian Plate and Indian Plate
• Plates collide and subduct under Eurasian Plate
• Location along plate boundaries makes it prone to earthquakes

Afghanistan is situated on the Eurasian tectonic plate. To its west, the Arabian plate subducts or pushes underneath the Eurasian plate. To the east, the Indian plate similarly subducts below the Eurasian plate. In southern Afghanistan, both the Arabian and Indian plates adjoin each other and subduct northwards under the Eurasian plate.

This complex tectonic setting means Afghanistan lies along the boundaries where major plates intersect and collide. The northward motion of the Arabian and Indian plates against the Eurasian plate leads to intense compression and deformation of the crust. This continuous convergence results in the building up of enormous stresses that are frequently released in the form of earthquakes.

Along the western and eastern boundaries, the sinking of the Arabian and Indian plates drags the Eurasian plate down, causing friction and displacement. The subduction zones along these colliding plate margins are seismically active areas prone to regular tectonic jolts. The interaction between the adjoining plates subjects Afghanistan to persistent tectonic activity and earthquakes of varying magnitudes.

Being situated over multiple plate boundaries makes Afghanistan highly susceptible to seismic events. The ongoing tectonic processes along its margins ensure that earthquakes remain a recurring threat in the region. The compressive forces exerted by the surrounding plates converging on the Eurasian plate produce ideal conditions for earthquakes to occur frequently.

Recent Earthquake Sequence Further Highlights Tectonic Complexity

The recent series of four 6.3 magnitude earthquakes in Herat, Afghanistan occurred along the same east-west striking fault over a period of a week. These shallow ‘multiplets’ ruptured different segments of the same regional thrust fault caused by the northward collision of the Indian plate into Eurasia. The release of stress along one portion of the fault can load stress onto adjacent sections, triggering subsequent earthquakes.

As thrust faults, these earthquakes are uplifting parts of the fault and surrounding region through cumulative deformation. The occurrence of multiple large earthquakes along the same fault in a short timespan highlights the immense tectonic stresses building up and sporadically discharging in this complex zone of active mountain building. This further explains why Afghanistan is prone to frequent seismic activity.

Complex Mountain Ranges

• Hindu Kush Mountains formed by Indian-Eurasian collision
• Pamir Knot – tectonically complex region
• Mountain building processes create faults and weaknesses

The Hindu Kush mountain range running through Afghanistan is an example of the complex tectonic processes occurring in the region. The Hindu Kush has been formed by the ongoing collision between the Indian and Eurasian plates. As the Indian plate pushes against the Eurasian plate, it leads to the folding and uplift of the Himalayas. This immense compressive force is also transmitted to the Hindu Kush mountains further west, resulting in the creation of faults and fractures.

The Pamir Knot marks the junction of the Himalayas, Hindu Kush, Karakoram, and Tien Shan mountain ranges. It is an exceptionally intricate geological region where the Eurasian and Indian plates twist around each other. The extreme compression and deformation occurring here makes the Pamir Knot prone to seismic disturbances.

In general, the mountain ranges in Afghanistan emerge from tectonic plate interactions. The crunching of plates against each other with massive force over millions of years folds, buckles, and lifts up the Earth’s crust, forming tall mountain belts. This orogenic process produces extensive fractures, faults, and weaknesses in the crust. The continuous strain placed on these faults by ongoing mountain building leads to tremors as the faults slip and readjust. The complex geological processes forming Afghanistan’s mountains are therefore responsible for much of the region’s seismic susceptibility.

Major Active Fault Systems

• Chaman Fault
• Main Pamir Thrust
• Other local faults produce earthquakes

Several active fault systems running through Afghanistan contribute to its frequent seismicity. One major fault is the Chaman Fault system near the Afghanistan-Pakistan border. It is an active transform boundary where the Indian plate grinds northward alongside the Eurasian plate. The side-by-side motion of plates builds up stress in the fault zone leading to earthquakes. The Chaman Fault has produced several devastating earthquakes, including the 1505 Kabul earthquake that killed 30,000 people.

The Main Pamir Thrust is another significant fault generating earthquakes in northern Afghanistan. This fault demarcates the boundary where the Indian plate subducts below the Eurasian plate. The thrust fault dips at a low angle and allows the rocks to slide over each other, producing earthquakes. The Main Pamir Thrust has been the source of major historical earthquakes like the 1902 and 1911 earthquakes.

Apart from these regional fault systems, many local faults crisscross Afghanistan. Local faults develop due to the regional tectonic stresses imparted by the collision and subduction of plates. As plates jostle against each other, they fracture the crust, forming innumerable small faults throughout Afghanistan. Displacement of rocks along these smaller faults also unleashes earthquakes frequently.

The presence of active regional fault systems combined with a plethora of local faults creates ideal conditions for repeated earthquakes in Afghanistan and surrounding areas. The high density of faults generates frequent seismic shocks that contribute to making Afghanistan one of the most earthquake-prone regions globally.

Earthquake Fundamentals

What Causes Earthquakes

• Build up and release of stress along faults and plate boundaries
• Slippage and displacement between plates

The fundamental cause of earthquakes is the build up and sudden release of stresses in the earth’s crust. Most earthquakes occur along faults, which are fractures or zones of weakness in the crust. Faults can exist between tectonic plates or even within a single plate.

As tectonic plates move and collide with each other, they cause the rocks of the crust to slowly deform. This deformity builds up stored energy in the rocks similar to a compressed spring. The rocks on either side of the fault are strained until their accumulated stress exceeds the frictional forces holding them in place. Then, the fault ruptures, resulting in an abrupt slippage and displacement of the rock masses on either side.

The slipping rocks radiate energy through seismic waves, causing the ground to shake violently. The point where the rupture initiates is called the focus or hypocenter of the earthquake, while the point directly above it on the surface is the epicenter. The magnitude of slippage and the amount of energy released determine the intensity of shaking during an earthquake.

In Afghanistan, the northward collision of the Indian and Arabian plates against the Eurasian plate slowly strains the crust. This relentless plate motion leads to deformation that accumulates along the faults marking the plate boundaries. When the elastic strain eventually overcomes the friction, it causes the faults to suddenly slip and generate an earthquake. The tectonic forces operating in Afghanistan produce ideal conditions for the build up and discharge of seismic stresses resulting in frequent earthquakes.

Key Concepts

• Epicenter, hypocenter, fault plane, seismic waves

The epicenter is the point on the earth’s surface directly above the hypocenter or focus, which is the underground point where an earthquake originates due to fault rupture.

The fault plane is the fracture surface where the rocks slip past each other during an earthquake. It may be vertical, horizontal, or sloped at an angle.

Seismic waves are the vibrations produced by an earthquake that travel through the earth’s interior and along its surface. The different kinds of seismic waves like primary, secondary and surface waves shake the ground during an earthquake.

Impact on Afghanistan

Contributes to Destructive Potential

• Active tectonics and frequent seismicity
• Remote mountain towns vulnerable to shaking
• Poor infrastructure unable to withstand damage

The active tectonics and high frequency of seismic shaking in Afghanistan significantly aggravate the devastation caused by earthquakes. The constant grinding of tectonic plates results in persistent release of stresses through recurring earthquakes of varying intensities. This exposes communities to repeated earthquake hazards.

Moreover, the remote mountain towns situated amidst rugged terrain are especially prone to extensive damage when earthquakes strike. The mountain slopes are unstable and prone to accentuated seismic shaking and landslides. The mud, brick and timber houses located on steep mountainsides cannot withstand severe ground motion. Entire villages are wiped out as buildings crumble during strong earthquakes.

Much of Afghanistan’s infrastructure is poorly engineered and constructed to be earthquake resilient. Buildings, roads, bridges and facilities are unable to withstand seismic shaking without extensive damage. Houses and structures built from substandard materials using inadequate construction practices are at highest risk of collapse. The lack of adherence to earthquake-resistant building codes renders communities extremely vulnerable.

These factors together aggravate the death toll and destruction unleashed by earthquakes in Afghanistan. The high frequency of seismic activity, remoteness of settlements, and fragile infrastructure combines to escalate the devastating impacts of earthquakes.

Exacerbates Humanitarian Crisis

• Displaces populations and disrupts essential services
• Hinders rescue and recovery efforts
• Compounds struggles with poverty, hunger, health

The earthquakes devastating Afghanistan have further exacerbated the existing humanitarian crisis in the country. Frequent earthquakes displace large populations as homes crumble, forcing people to abandon their villages. Over a million Afghans have been displaced internally by the recent quakes. This disrupts access to essential services like healthcare, education and livelihoods.

Rescue, relief and rehabilitation efforts following major earthquakes are severely hindered by infrastructure damage. With roads blocked by debris and landslides, delivery of aid is obstructed. Lack of communication networks due to collapsed mobile towers also hampers rescue operations.

The earthquakes compound the struggles of Afghans who already face tremendous poverty, hunger and health problems. Over half the population is dependent on humanitarian assistance. With limited local capacity for rescue and reconstruction, the earthquakes have magnified these problems. Food shortages will grow with loss of agricultural land and stored harvests. The crisis has been further intensified by the displacement of families into makeshift camps.

Final thoughts

• Afghanistan’s complex tectonic setting makes it prone to frequent, destructive earthquakes
• Ongoing plate motions ensure seismic hazard will continue
• Need for preparedness, resilient structures, and regional cooperation

Afghanistan’s location at the junction of the Eurasian, Indian, and Arabian plates renders it highly prone to frequent and destructive earthquakes. The complex tectonic interactions between these plates subject Afghanistan to intense seismic activity. The northward subduction of the Indian and Arabian plates under the Eurasian plate continues, ensuring that devastating earthquakes will remain an ever-present hazard.

Going forward, it is imperative for Afghanistan to invest in preparedness and mitigate seismic risks. Earthquake-resilient construction practices need to be strictly implemented to make infrastructure and buildings better able to withstand shaking. Strengthening regional cooperation on disaster management will augment Afghanistan’s capacity to respond to earthquakes. While the underlying tectonic forces cannot be controlled, preparedness and preventive action can help save Afghan lives and livelihoods from future earthquake disasters.