Stress is growing. A major Himalayan quake is coming. But when?

It is this eerie silence that most seismologists studying the Himalayas are worried about.

They have been fearing 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. They are worried about the devastation it can cause on human lives and material wealth across North India.

It was this obvious question that pre-occupied top earth scientists and seismologists in the country 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?”. By a ‘big one’, the scientists meant an earthquake of more than eight on the Richter.

“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.

Supriyo Mitra, professor of Earth Science at the Indian Institute of Science Education and Research (IISER), Kolkata, agrees.“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 Mitra.

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, helping the scientists precisely locate the stretch along the Himalayas where those big earthquakes can happen,” said the IISER professor.

‘Certainty of punishment’

While it is difficult to prevent such natural calamities from taking place, it would be possible to reduce the material destruction as well as the loss of human lives, by making man-made structures earthquake resistant. “Calculations have shown that spending an extra 10 per cent buildings in the Indo-Gangetic plains can be made to withstand earthquakes of the magnitude of 8,” said Mitra.

The lack of enforcement of code for earthquake-resistance while constructing buildings in seismic-prone zones is worrying 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.

“...builders and engineers violate such codes, but they were allowed to get away with minor penalty or punishment. It’s time to realise that it is not ‘certain punishment’ but ‘certainty of punishment’ that would force them construct safe buildings,” Rai said.