Geologists are divided over the megaquake threat to the Himalayan region

New Delhi, Nov. 11: A silent accumulation of subterranean strain under southern Tibet may trigger megaquakes in the Himalayas, US scientists have said, challenging existing notions about earthquakes in the Himalayan region.

Using computer simulations, geologists Roger Bilham and Nicole Feldl at the University of Colorado in Boulder have shown that the strain build-up under Tibet could lead to megaquakes of magnitude 8 or higher with the potential for catastrophic damage.

Scientists have known for decades that the collision of the Indian continental plate with the Asian plate leads to underground strain. At critical “breaking points” when the strain shoots past certain limits, the release of this energy shows up as earthquakes.

In a paper published in the journal Nature on Thursday, the geologists said megaquakes in the Himalayan region might occur at intervals of about 1,000 years, emptying strain energy accumulated in southern Tibet.

“We’ve always assumed that earthquakes in the region were driven by the release of energy accumulating near the Great Himalayas,” said Bilham, who specialises in Himalayan earthquake mechanisms. “Our calculations suggest that a substantial volume of the southern Tibetan plateau plays a significant role in driving great ruptures.”

“This study indicates that even when large earthquakes have released strain in the Himalayas, there might be an even bigger reservoir of strain energy in Tibet that could lead to megaquakes,” said Vinod Gaur, a geophysicist at the Indian Institute of Astrophysics in Bangalore.

However, geologists also caution that this Tibetan hypothesis still needs to be validated.

“It is not clear whether and how much of the strain under the Tibetan plateau will lead to earthquakes in the Himalayas,” said Shyam Rai, a scientist at the National Geophysical Research Institute in Hyderabad.

With available knowledge, scientists cannot predict when the strain build-up will reach breaking point. But a megaquake of magnitude 8 or higher would mean “catastrophic damage”, said Malay Mukul at the Centre for Mathematical Modelling and Computer Simulations in Bangalore.

Last year, an earthquake of magnitude 7.4 had killed more than 70,000 people in Kashmir.