The Hindu : Opinion / Editorials : PREPARING FOR EARTHQUAKES

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Friday, Apr 08, 2005

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PREPARING FOR EARTHQUAKES

SOME 40 MILLION years ago, the plate bearing India began colliding with the one carrying Eurasia. The mighty Himalayas rose as a result of this ongoing collision and the Tibetan plateau is thought to have been pushed up by as many as three kilometres over the last 10 million years. The rise of this majestic mountain range and the adjacent plateau led to the onset of the Asian monsoon some eight million years ago. As the Indian plate continues to push into Eurasia, fearful stresses accumulate at the faults marking the boundaries between the two plates. For long periods, the two plates remain locked together, rather like Sumo wrestlers trying to get the better of each other. Then suddenly, when the strain becomes too great, one or more of the faults rupture, setting off an earthquake and allowing a bit of the Indian plate to slip beneath Eurasia. When the rupture happens under the sea, as it did on that fateful morning on December 26, 2004, it can set off a tsunami.

Global Positioning System (GPS) receivers that accurately monitor the position of places on either side of the plate boundary provide an indication of the strain that is building up. This combined with estimates of the strain released by past earthquakes gives researchers an indication of which faults are most likely to rupture again. A leading geologist has estimated that sufficient strain had accumulated at about a dozen places across the Himalayas to drive a `great earthquake' (one with a magnitude greater than 8). However, no one can predict when or precisely where such an earthquake will happen. But earthquakes tend to cluster in time and space, with one earthquake redistributing stresses and causing another nearby fault to act up. There are active fears that December's earthquake might also push faults in the Himalayas, already teetering on the edge, into rupturing. A great earthquake in the Himalayas could claim tens of thousands of lives.

It is not as though dangers to India from earthquakes are restricted to the plate boundaries. Faults marking weak zones within the Indian plate can also fail, as happened at Bhuj in Gujarat on Republic Day 2001 when about 20,000 people died. Over 60 per cent of the Indian landmass is liable to be affected by earthquakes of various intensities. Many of India's populous cities, including Delhi, Mumbai and Chennai, are located in zones with considerable seismic risk. A government document remarks grimly: "Some of the most intense earthquakes of the world have occurred in India, but fortunately, none of these have occurred in any of the major cities... Typically, the majority of the constructions in these cities are not earthquake resistant. Thus any earthquake striking in one of these cities would turn into a major disaster." It will be prudent not to push that sort of luck too far. Considering how much of the country and its people are vulnerable to earthquakes, a serene unawareness in the face of these risks is deeply disturbing. Creating the necessary awareness at all levels in vulnerable cities, towns, and villages must be the top priority. Only then can measures to make buildings and other types of construction better able to withstand earthquakes really take root.

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