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22nd, March 2023 incident
On the evening of 22nd March 2023, the National Capital Region (NCR) of India, including Delhi, experienced strong earthquake tremors. The earthquake measured 5.3 on the Richter scale, with its epicenter being 12 kilometers deep in the earth’s crust, in the Sonipat region of Haryana.
The seismic activity, which lasted for about 30 seconds, was felt by residents across Delhi and NCR, causing panic and chaos. Many people were seen rushing out of their homes and buildings, while others reported the shaking of furniture and other household items.
The earthquake also led to the disruption of electricity and communication networks in some areas. The Delhi Metro services were also temporarily halted as a precautionary measure.
According to the Indian Meteorological Department (IMD), the earthquake was of moderate intensity, and no major damage to life or property was reported. However, the tremors were felt across a wide area, including Delhi, Noida, Ghaziabad, and Gurgaon, which falls under the seismic zone IV, characterized by high to moderate seismic activity.
The earthquake has once again highlighted the need for better preparedness and awareness among people living in earthquake-prone areas. Governments and authorities need to take adequate measures to mitigate the impact of earthquakes, including enforcing building codes and conducting regular awareness campaigns.
Why Delhi experiences frequent earthquakes?
First of all you have to understand that it is impossible to predict an earthquake. You can only record data and find out the epicenter of the earthquake. But that is not going to help you in predicting when the next earthquake is going to come or from where it is going to come.
However, there is a General as well as larger prediction that all the earthquakes recorded in Delhi-NCR region are due to the release of energy through the faults that exist deep in the earth’s crust when Indian Plate collided With The Eurasian plate some 40 to 50 million years ago.
So let me begin from that story and then slowly step by step come to the present scenario. You all know the story right? Some 40-50 million years ago, two large land masses India and Eurasia driven by plate movement collided.
Always remember, when we breakdown different layers of the Earth surface, we have the inner core, the outer core, then the inner mantle and the outer mantle, and finally the crust.
Earth’s crust is further divided into two types: oceanic crust and continental crust.
And just below the oceanic and continental crust, there is a thin layer of upper mantle which is very similar to earth crust. The whole of crust and the thin portion of the upper mantle is together known as lithosphere. It is the solid, outer part of the Earth. The lithosphere includes the brittle upper portion of the mantle and the crust, together it is the outermost layers of Earth’s structure.
Right below the lithospehre, there is a layer of upper mantle called the asthenosphere. This is made up molten rock, it is much hotter and the entire layer can move like fluid.
So what happened was, around 225 million years ago (Ma) India was a large island situated off the Australian coast and separated from Asia by the Tethys Ocean. The supercontinent Pangea began to break up 200 Ma and India started a northward drift towards Asia.
80 million years ago the Indian Plate was 6,400 km south of the Eurasian plate. It was moving towards north at a rate of between 9 to 16 cm per year. And how was it moving? At that Thetys ocean was subducting. That means an oceanic plate was moving under the the large Eurasian Continental plate. If I have to say this in a more Technical sense, the asthenosphere which is a layer of the upper Mantle that was moving towards the northern direction and that too moving right under the the huge Eurasian plate.
When this oceanic plate was moving under the large Eurasian Continental plate, it was also pulling the Indian Plate which is attached to it. When this was happening there was a lot of explosive volcanic activity that was taking place on The Eurasian plate. Also, a lot of ocean floor sediments was being pushed on to The Eurasian continent. These scraped-off sediments are what now form the Himalayan mountain range. This accumulation of ocean floor sediment onto a continent during subduction is called accretionary wedge.
From about 50-40 Ma the rate of northward drift of the Indian continental plate slowed to around 4-6 cm per year. This slowdown is marked as the beginning of the collision between the Eurasian and Indian continental plates, in other words the closing of the former Tethys Ocean, and the uplifting of Himalayan mountains.
As soon as the Tethys ocean was sealed up. Both the Indian as well as The Eurasian Continental plate crumbled and started folding. That’s what created the Himalaya and the Tibetan Plateau. You have to understand that these Continental plates at an average were around 75 kilometre thick. When such a thick Continental mass collided just imagine the intensity behind it. This kind of massive impact had also shut all the volcanic vents around the region.
If you look at the type of rocks that are found in Himalayas you will find granite. And we all know granite is basically formed when magma solidifies. So anyhow the crashing of both the continental mass has sealed all kinds of volcanic activities around that region so that it does not reaches the surface.
We also know that the Himalayas are still rising by 1cm per year as India continues to move northwards into Asia.
No before I go further I need to go back to the point this Continental plates at an average were around 75 kilometer thick. When they collided and crumbled that’s how the Himalayan mountain were formed.
Now I want you to imagine, what happens when two thick blocks of landmass collides and crumble. It will develop deep fractures, cracks and fault line. Some of it you may see it on the surface, while some of them might be hidden in deep layers of the crust.
Now if you understand this. Let’s go to the regular map and let me show you the main Himalayan fault line.
We all have read that the Himalayan mountains ranges consists of three parallel ranges. The Greater Himalayas known as the Himadri, the Lesser Himalayas called the Himachal, and the Shivalik hills, which comprise the foothills.
So all you need to do is look at the Shivalik Hills from north west extension to the Eastern extension. You will find the Shivalik Hills in lower districts of Himachal Pradesh, Uttarakhand, Nepal, Sikkim, Bhutan and Arunachal Pradesh. Below the Shivalik Hills, you’ll find the Ganga plain and in the Eastern part you’ll find the Brahmaputra plain.
That means the Shivalik Hills are the boundary line of Himalayan mountains. If I have to take a rough measurement from the foothills to the greater Himalaya. The distance will be somewhere around 200 kilometre. That means the collision of the Indian Plate And The Eurasian plate caused ripples on both the landmass. But if you look at the Indian Plate the ripples went some 200 kilometer backward because that’s where the Shiwalik hills are, and after that plain areas begins. You can also call this boundary as Himalayan folded belt.
There must be so many fault lines in the deep layers of The crust that branches out from this Himalayan fault line or Himalayan folded belt. Some of the well known fault lines near Delhi are – Mathura fault; Moradabad fault; Delhi Haridwar ridge; Delhi Sargoda fault; Mahendergarh and Dehradun fault.
These are just few discovered ones. There are many more such fault lines which are not yet discovered. So the existence of such fault lines make Delhi region vulnerable. Because if you look closely these faults and fractures are held by rock layers. When enough stress builds up and the rocks deform or crack, break or suddenly slips, the entire block of land which was resting on it suddenly slips and drops, it releases energy in waves that travel through the layers of the crust and causes the shaking that we feel during an earthquake.