New Delhi: Sunday’s 6.8 magnitude earthquake on the Sikkim-Nepal border has wreaked havoc in the Himalayan country and the north- east Indian state, but scientists say the likelihood of a much greater earthquake in north India remains.
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Despite a decade-long upgrade of seismic monitoring instruments, scientists say their data is insufficient to be able to predict quakes anytime this decade.
“Technically, this is classified as a moderate quake (with a magnitude less than 7); however a great quake (above 7.5 on the Richter is imminent in this region. Unfortunately, we can’t predict when,” said Ajit Tyagi, director general, India Meteorological Department.
An earthquake that registers a 7 on the Richter scale releases about 30 times more energy than one that measures 6. An earthquake of magnitude 6 releases 60 times the energy contained in the atomic bombs that destroyed Hiroshima in 1945. The 18 September quake with an epicentre in North-west Sikkim caused tremors in Assam, Meghalaya, West Bengal, Bihar, Delhi and parts of Nepal. The main shock was followed by two aftershocks recorded within an hour of each other. At least 52 people have been killed in Sikkim, West Bengal and Bihar in the quake. Most major phone networks lost at least 25% of their operational capabilities in Sikkim. The total economic loss of the states has yet to be ascertained, home secretary R.K. Singh said at a briefing in Delhi on Monday. He added that power supply in Sikkim, which had been disrupted on Sunday evening, was largely back on track.
Photo by Reuters; Graphic by Sandeep Bhatnagar/Mint
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The conviction of seismologists that a major quake is imminent in the region rests largely on historical precedent. Between 1897 and 1950, India saw five devastating earthquakes between and 7.9 and 8.5 on the Richter scale and the subsequent 60 years haven’t seen anything on a comparable basis. Scientists infer that this is too long a time without a temblor of significant size in the region. Sikkim as well as most of north India falls in zones 4 and 5, regions classified as highly vulnerable to high intensity quakes.
“There have been several earthquakes of 6 and 7 magnitude in that period, but together all of them hardly add up to the intensity of one major quake. That energy has to come out somewhere and it’s only a matter of time,” said Harsh Gupta, a former director with the National Geophysical Research Institute, Hyderabad.
Young monks walk past a damaged house after a 6.9 magnitude earthquake in Gangtok on September 19. Reuters photo
Most of north India lies along a zone called the Main Central Thrust Zone, a region that spans the Himalayas and extends well into Pakistan. It’s on this zone that the tectonic plates that support India collide with the ones that bear Europe. The collision between these two plates leads to great instability, that, according to scientists, greatly increases the chances of frequent, major earthquakes.
Even though India doesn’t see as many significant earthquakes as parts of the US or Japan, it has lost several thousand lives to earthquakes in the 20th century, mostly because of the absence of resilient infrastructure.
India is “likely to take between 10 to 15 years to reach a minimum satisfactory level in terms of preparedness for earthquakes,” Nirmal Chander Vij, former vice-chairman of the National Disaster Management Authority, said in a note published on the organization’s website that was reported by Mint on 29 April. “Some very serious shortcomings persist in the preparedness levels because of our overall complacency towards this subject (preparedness for high-intensity earthquakes).”
A woman carrying her child to school walks past quake-damaged houses in Bhaktapur on September 19. Reuters Photo
Gupta said it was far easier to put in place plans to prepare for a quake than being able to predict one anytime soon.
“We do know the speed at which the Indian plate is crashing into the Eurasian plate thanks to better monitoring facilities, but that’s still not enough to make predictions,” Gupta said. “There’s a lot, however, that can be done to restrict damage.”
Sahil Makkar contributed to this story.