Next tsunami for India may be from West

Bangalore, Feb 25: The Indian sub-continent could face the next tsunami threat from the West and not the East as the 500 km fault line along Baluchistan remained dangerously vulnerable to earthquakes of high magnitude, according to a noted geophysicist and Crawford Prize winner, Dan McKenzie.

''This rapture zone, lying East to West near South Iran, is much narrower compared to the 1,200-km-long weak zone along the Indonesian island, where the 9.1 magnitude earthquake triggered a tsunami that devastated the East coast of India and Sri Lanka in December 2004. However, this has remained silent for long and pose a live danger to the West coast of India,'' he opined.

Delivering a lecture on 'Living with Earthquakes' at the Indian Institute of Science here, he said nobody knew when it 'moved' in the recent past, but it was a potential danger to the West coast of the sub-continent as an earthquake of even a small magnitude could trigger a tsunami.

Prof McKenzie said the North Indian belt was one of the most dangerous belts prone to earthquake and the cities in this part of the country faced a major threat due to dense population.

He felt that educating people about the dangers posed by tsunamis could go a long way in minimising loss of life. While some structured buildings remained unscathed, like a mosque in Southern Sri Lanka, fishing villages on the coast were wiped out. As soon as there was a earthquake of the magnitude that could trigger a tsunami, the sea level would first go down, before the sub-surface waves moving at over 500 km per hour hit the coast. ''At this time, people should run for life as a bulge in the sea will be the next step before the waves hit the coast,'' he said.

Prof McKenzie said the best way to effectively face an earthquake situation was to build quake-resistant buildings. ''It makes economic sense to build quake-resistant houses than spend millions of Dollars in predicting an earthquake, which is next to impossible. Turkey spent ten million Dollars, while the United States spent 200 million in trying to develop a technology to predict earthquake. It never worked. It cost only 10 per cent extra to build quake-resistant houses, which is constructed on steel plates that move with lead blocks beneath to absorb the shock. It has proved effective,'' he said.

Highlighting the advantages of quake-resistant buildings, Prof McKenzie said that while just 40 people died in the 1994 earthquake of 6.8 magnitude that struck Northridge, California, another quake of the same magnitude killed over 40,000 of the one lakh population of Ban city in Iran in 2000.

Buildings built on bed rocks were less vulnerable to earthquakes than those built on soil base. Taking the example of Tehri dam in Uttarakhand, he said dams built on fault zones should essentially be earth dams as concrete dams could give way easily in the eventuality of earthquakes.

Tehri dam is located in the Central Himalayan seismic gap, a major geologic fault zone. This region was the site of a 6.8 magnitude quake in October 1991, epicentered 50 km from the dam.

UNI