ISLAMABAD: The powerful earthquake of 5.8 magnitude that stuck northeast Pakistan on September 24, 2019 killed around 37 people and injured scores of others, is not the last one to hit the area.
This earthquake with its epicentre near densely populated areas of Azad Jammu and Kashmir and Punjab had a very shallow depth of 10 km. Accordingly to US Geological Survey (USGS), more than 20 million people were exposed to it, had the intensity or the duration been longer, it would have cause damages.
The government yet to determine the exact details of material losses, it is estimated buildings worth billions of rupees were either completely or partially damaged -hundreds of them not liveable anymore.
The subcontinent (South Asian region comprising Pakistan, India, and Afghanistan) has suffered some of the largest earthquakes in the world with more than about 60 percent of its land area prone to shaking of devastating intensity of VII and above on the MMI scale, a seismic intensity scale.
In fact, the entire Himalayan belt is considered prone to great earthquakes of magnitude exceeding 8.0, with Kashmir region among the most susceptible.
The region lies on the boundary, where the small Indian plate that underlies most of Pakistan and India and the vast Eurasian tectonic plates that consist of Europe, Russia and most of Middle East, collide.
September 24th earthquake occurred as the result of shallow reverse faulting near the convergent boundary between the Indian and Eurasian plates. It was the same natural phenomenon that triggered the October 8, 2005 earthquake.
What is a Reverse Fault:
A reverse fault is one in which one side of the fault, the hanging wall, moves up and over the other side, the foot wall. This movement is caused by compression and is common at tectonic plate boundaries. A thrust fault is a reverse fault that is at an incline of less than 45 degrees. Tensional stress is when rock slabs are pulled apart from each other, causing normal faults. With normal faults, the hanging wall slips downward to the footwall. This causes reverse faults.
What is Indian Tectonic Plate:
The Indian tectonic plate is located in the north east hemisphere. It is bounded by 4 major tectonic plates. North of the Indian plate is the Eurasian plate, to the South East, the Australian plate, to the South West, the African plate and to the West the Arabian plate.
Are these Plates Active Today:
Yes – Earthquakes occur in the northern part of the Indian plate as it is still active and drifts at a velocity of about 5 cm per year. Low to 5 magnitude earthquakes were registered in the urban areas of India.
The largest recorded earthquake occurred near New Delhi in 1950 and had a magnitude of 8.5. The devastating M 7.6 earthquake on October 8, 2005 occurred 160 km to the north of September 24th event, also was a result of shallow reverse faulting.
October 2005 earthquake killed at least 86,000 people and caused extensive damage in northern Pakistan. Few other large events have occurred in recent decades in the immediate vicinity.
Six earthquakes of magnitude seven and greater have occurred during the past 40 years some 400-500 km to the northwest in Northastern Afghanistan, mostly at intermediate depths of 100-250 km. The recent most was 7.5 magnitude earthquake in October 2015 that resulted in at least 395 fatalities, more than 1000 injuries, and the destruction of tens of thousands of buildings.
What Happens When Both Plates Collide:
Earthquakes and active faults in northern Pakistan and adjacent parts of India and Afghanistan are the direct results of collision between Indian and Eurasian Plates.
Collision of the Indian and the Eurasian Plates had resulted in some of the biggest geological changes on earth. Their collision about 50 million years ago resulted in the erection of the Himalayan mountain chain which contains the highest peaks on the Earth today.
Another result of the collision of the two plates is the creation of a multitude of small plates in the eastern boundary of the Indian plate. As the India plate moves northward, it is pushed beneath the Eurasia plate. At the location of most recent earthquake, the India plate converges with the Eurasia.
Much of the compressional motion between these two colliding plates has been and continues to be accommodated by slip on a suite of major thrust faults that are at the Earth’s surface in the foothills of the mountains and dip north-northeastward beneath the ranges.
These include the Main Frontal Thrust, the Main Central Thrust, the Main Boundary Thrust, and the Main Mantle Thrust. These faults have a sinuous trace as they arc across the foothills in northern India and into northern Pakistan. Active faulting is accommodated by a large system of faults.
Most Recent Earthquakes in the Region:
It should be cause of great concern for people in Pakistan that there have been multiple earthquakes of minor to severe intensity in the past few months.
Because of tectonic movements significant tremors and jolting was witnessed in Chaman, Balochistan and Sukkur, Sindh recently. Overall, there were 14 earthquakes in the past 30 days and 129 earthquakes in the past 365 days across Pakistan.
Below is a list of earthquakes that had occurred in the past one month or so in Pakistan, India and Afghanistan region.
September 24: 5.6 magnitude, 10 km depth Jhelum, Punjab, Pakistan.
Three days before that: 4.5 magnitude, 210 km depth Jurm, Badakhshan, Afghanistan.
Eight days before that 4.2 magnitude, 199 km depth Jurm, Badakhshan, Afghanistan.
12 before that 4.5 magnitude, 116 km depth Jurm, Badakhshan, Afghanistan.
13 days before September 24th earthquake: 4.8 magnitude, 258 km depth Jurm, Badakhshan, Afghanistan.
14 days before it 4.5 magnitude, 222 km depth Jurm, Badakhshan, Afghanistan.
16 days before 4.9 magnitude, 35 km depth Bhadarwāh, Indian Held Kashmir.
17 days before 4.2 magnitude, 188 km depth Jurm, Badakhshan, Afghanistan.
17 days before another 4.8 magnitude, 10 km depth Bhadarwāh, Kashmir, India.
19 days before 4.3 magnitude, 228 km depth Jurm, Badakhshan, Afghanistan.
22 before 4.5 magnitude, 203 km depth Jurm, Badakhshan, Afghanistan.
27 days before 4.0 magnitude, 10 km depth Chaman, Balochistān, Pakistan.
29 days before 4.3 magnitude, 198 km depth Jurm, Badakhshan, Afghanistan
About a month before 4.5 magnitude, 10 km depth Kotri, Sindh, Pakistan
Two months before 5.2 magnitude, 106 km depth Khorugh, Gorno-Badakhshan, Tajikistan.
And the list goes on and on.
This data shows at how much serious risk our region. The governments and the people of the can mitigate potential losses by adopting precautionary measures. Strict implementation of building codes and ensuring earthquake resistant infrastructure is the most important step. After 2005 earthquake, the authorities were moved for the time being. Building codes were formulated at least for the federal capital but their implementation was forgotten like most other decisions we make in firefighting mode.
(The writer is director of Pakistan Centre for Development Communication.)
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