New Delhi: Three leading American seismologists have cautioned that future damaging earthquakes can occur in Central India, where no quakes have been so far recorded because this part of India is "flexed" like a bow.

The scientists – Roger Bilham, Rebecca Bendick and Kali Wallace of the University of Colorado – say the Indian plate is flexed downward by the weight of the Himalaya on the one hand, and by the buckling effect of the plate's collision with Tibet that started millions of years ago and is still continuing at the rate of 18 millimetres per year.

As a result, the earth's crust in the Central part of India is bulged out to make the subcontinent look as if it has developed a potbelly.

"The overall stress distribution in the flexed plate suggests that areas of Central India where no historic earthquakes are recorded may yet be the locus of future damaging events," they say in a report published in the September issue of the 'Proceedings of the Indian Academy of Sciences'.

They say severe variations in stress exist within the Indian plate as a result of the flexing. For instance, the surface is in tension from the crest of the flexural bulge northward, but is in the state of severe compression in the southward direction – that is the Central part of India.

The stress developed due to flexing is surprisingly large and is increasing northward towards the crest of the "bulge" and decreasing even more rapidly between the bulge and the Himalayan foothills, the scientists said.

According to their calculations, "The largest compression stresses are encountered by the surface of the Indian plate as it approaches the Himalayas." As India moves towards Tibet, every point in India passes slowly through the flexural stress field.

Their calculations indeed show that the Bhuj earthquake of 2001 occurred close to this region of maximum stress, as did the Latur earthquake of 1993. "The Koyna earthquake, though triggered by reservoir loading, is in the region of surface compressional stress," the scientists observe.

The stresses on the Indian plate result not only from its collision with Tibet, but also from the loading by sediments deposited in the Arabian sea in the West and in the Bay of Bengal in the East and from the flexural effects of India's descent beneath the Tibetan plateau. Since these forces are unique to India, they presumably explain why India exhibits anomalously high mid-plate seismicity compared to neighbouring plates, scientists say.

PTI