Threat of major earthquake over 8.0 magnitude looms over Himalayan arc

NEW DELHI: Following the gentle tremor in northern India on Friday, it has emerged that the entire Himalayan arc is poised to produce a sequence of great earthquakes over 8.0 magnitude. Human catastrophe in the region is likely to be unprecedented when these occur.

Reviews by Steven G Wesnousky, professor of geology and seismology at the University of Nevada at Reno, US, and Roger Bilham, geological scientist at Cooperative Institute for Research in Environmental Sciences (Cires) at University of Colorado, suggest that a big earthquake is needed to release the elastic energy in large sections of the Himalayan arc.

Bilham published a review of earthquakes in the Himalayas in the last 1,000 years, for The Geological Society in London. It shows that there haven’t been enough big earthquakes in this period to ease the accumulated strain in large sections of the arc.

It is estimated that due to the average rate of convergence between the Indian and Asian plates, every year adds additional strain on the Main Himalayan Thrust that needs an Mw = 7.3 earthquake for release (moment magnitude or Mw is a quantitative measure of an earthquake’s magnitude by size).

There have been strong earthquakes in western and central Himalayas in 100 years. But the quakes in Kangra (1905, Mw7.8), Uttarkashi (1991, Mw6.8), Chamoli  (1999, Mw6.8,) and Kashmir EQ (2005, Mw7.6) were actually moderate to major earthquakes. This means something more severe in nature might be in store.