Views from Experts.
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When havens turn into hells
We need to learn to build earthquake-proof homes. S.M.A. KAZMI reports on the lessons Gharwal learnt after its last major earthquake
Earthquakes do not kill people. Houses in which people live do. The earthquake of January 26 that flattened out Bhuj and a good part of Ahmedabad demonstrated this eloquently.
It’s useful to go back to the lessons that emerged from the earthquake that hit Garhwal in 1999, which killed more than 100 people and destroyed more than 10,000 houses in Chamoli, Rudraprayag, Tehri and Pauri districts. It had at that time raised an old debate: the construction of earthquake resistant houses, particularly in quake-prone areas.
Earthquakes are a reality in the Himalayan mountain region, which is one of the youngest, tallest and most fragile mountain systems in the world. The Himalayan region has been formed as a result of the collision of the Indian subcontinent, as it drifts northwards on earth’s surface, with the Eurasian plate. This process, which has been on for the past 60 million years and continues even today, is the major reason for earthquakes occurring here.
As Dr V.C. Thakur, director, Wadia Institute of Himalayan Geology, points out, seismic activity is constantly going on in the Himalaya and, on an average, nearly 200 earthquakes of smaller magnitude occur every year in the Uttarakhand region alone. Most of them go undetected by the local communities.
In this century alone, earthquakes of magnitudes greater than 6 on the Richter Scale, like the Uttarkashi one in 1991 and Chamoli in 1999, have struck the region 12 times. According to a simplistic estimate, an earthquake of a magnitude greater than 6 strikes the region about once in a decade.
Geophysicists are now fairly certain that a great earthquake of magnitude 8 or above would strike the central Himalayan region between Dehra Dun and Kathmandu sometime in the next century. The Dharchula-Bajang area on the Indo-Nepal border and Tehri-Uttarkashi region were identified as the most likely places. These warnings should be taken seriously.
But to go back to the old problem, all the deaths caused in the Uttarkashi, Chamoli and even Latur earthquakes, were due to house collapses. In the Uttarkashi quake, 65 per cent of the houses in the epicentral area either suffered heavy damages or completely collapsed. Similarly in Chamoli and Rudraprayag districts more than 10,000 houses suffered damages.
Dr Ravi Chopra, of the Dehra Dun-based People’s Science Institute, who has been involved in popularising earthquake resistant features and strengthening or retrofitting all existing buildings. For this to happen, it would be necessary to change the current construction practices in the Uttarakhand region, which are increasingly influenced by houses built in the plains. It requires major information dissemination campaigns on the concept, practical training of the local masons in earthquake resistant features and the building of a number of demonstration houses.
Dr Anil Joshi of the Himalayan Environmental Studies and Conservation Organisation (HESCO), who had been involved in the construction of quake resistant houses in Tehri and Rudraprayag districts on the guidance of renowned architect Laurie Baker after the Uttarkashi quake in 1991, said that all those houses remained intact while many other houses in the vicinity collapsed in this quake. Laurie Baker emphasised on building houses with local material. ‘‘Only the poor masonry work in the rural houses and ignorance of the traditional wisdom in the construction of the houses has resulted in the losses,’’ he maintained.
While a whole lot of government agencies and research institutions had been saying some thing or the other about the construction of quake resistant houses after the earthquake, nothing has been done practically on the ground.
Chopra explained that for the house to be quake resistant, they must have tie-bands at the plinth, lintel and roof levels to help a structure absorb the shocks as a single unit. Since corners are most vulnerable they should be strengthened. Elasticity of the structure could be enhanced by introducing flexible members-steel rods at corners. Openings such as doors and windows should be few, small and symmetrically placed away from the corners. The houses should also be kept as light as possible.
There are examples in the entire Himalayan belt stretching from Kashmir to the North-East of having traditional earthquake resistant houses using locally available material such as wood, stones and mud. These structures are called pherols in Garhwal and have withstood the test of earthquake for well over a hundred years in many cases. Such structures are not possible due to the shortage of wood and lack of traditional wisdom but still, with a little application, sufficiently safe houses could be built.
‘‘An additional expenditure of mere six to ten per cent during construction can make the building quake resistant,’’ according to Dr A.S. Arya, head of the quake engineering cell of the Bureau of Indian Standards (BIS). Professor P.S. Saklani, vice-chancellor of the Garhwal University, who himself is a geologist has called for suitable legislation to ensure that people adhered to the quake resistant norms.
Several high level meetings have been organised to devise strategies to deal with the housing problems faced by the victims and also to ensure that houses rebuilt adhered to the basic quake resistant norms. But the fact is that after the hue and cry that greets every disaster settles down, nothing concrete is done on the ground.
The latest disaster in Gujarat has highlighted once again the need for long-term planning and internalising the wisdom of the ages into our construction practices. And here we have another problem to address. The need to make highrise buildings in downtown locations resistant to earthquakes. It’s now back to the old drawing board.
Source :
www.indianexpress.com/ie/daily/20010222/focus.htm
