From C K Nayak
NEW DELHI: Seismologists and scientists are unanimous that a big earthquake is imminent in the Himalayan region and they are also sure of its large scale devastation but do not know when.
They have feared a great earthquake along the 600-km stretch of the central parts of the Himalayan region for some time. They know that it is in the offing, but cannot say when it will happen, but are worried about the devastation it can cause on human lives and material wealth across this part of the globe.
This was the mood that pre-occupied top earth scientists and seismologists who attended an international conference at the Indian Institute of Technology (IIT) Mandi last week.
The question that they wanted to ponder over was: “Are we ready for a big one?” – a quake measuring over eight on the Richter Scale.
“There is a consensus among all seismology groups, including international ones studying the Himalayas, that a great earthquake is imminent. The studies have clearly indicated the strain that is building up and the earthquakes that have occurred in the recent past have not been enough to release this strain,” said CP Rajendran, professor at the Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru.
The earthquakes that happened in Nepal in 2015 or Uttarkashi (1991) or Chamoli (1999) were large ones, no doubt. But a big one hasn’t occurred for a very long time, said Rajendran, one of the speakers at the IIT- Mandi conference.
“I believe we are entering a period of earthquake generation in that area. With the explosive increase in population and a disregard for safety, a relatively large earthquake can be quite disastrous for the region,” he said.
“We know very well where these earthquakes are going to happen with what sort of intensity. But it is difficult to say when will it happen,” said Supriyo Mitra, professor of Earth Science at the Indian Institute of Science Education and Research (IISER), Kolkata. The Himalayas, one of the youngest and active mountain ranges in the world, rose when the Indian tectonic plate rammed against the Asian plate.
As there is a difference in the relative movements of these two plates, the faster moving Indian plate is pushing under the Asian plate, prompting the Himalayas to gain height continuously, albeit in a small measure. As the Indian plate ducks under the Asian plate, the friction between the plates is stored as strain energy, which needs to be released every now and then.
The small earthquakes that happened in the past clearly indicate where the strain is building up, they said.
This helped the scientists precisely locate the stretch along the Himalayas where those big earthquakes can happen. It is next to impossible to prevent such natural calamities from taking place, the scientists agreed.
But it would be possible to reduce the material destruction as well as the loss of human lives, by making man-made structures earthquake resistant, they added.
The lack of enforcement of code for earthquake-resistance while constructing buildings in seismic-prone zones is worrying, said Durgesh Chandra Rai, professor of civil engineering at IIT-Kanpur.
Rai’s team found that a large number of public structures damaged during the Sikkim, Kashmir and Manipur earthquakes lacked proper enforcement of building codes.
Himalayan earthquakes fall into two main types – moderate intensity quakes like the ones in 2015 and 2008 and gigantic upheavals like the 8.3 magnitude in 1934 and 1950. The first ones are accompanied by a lot of shaking, but do not deform the surface.
But the gigantic upheavals like the 8.3 magnitude 1934 quake with epicenter in eastern Nepal destroyed much of Kathmandu, and the 8.7 magnitude Assam earthquake in 1950 is described as the greatest earthquake to hit the Himalayas in recorded history.