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Himalayan quakes devastate larger areas: expert

Shireen in Hyderabad

Eminent seismologist B K Rastogi of the Hyderabad-based National Geophysical Research Institute said that Monday's earthquake was one of the major quakes to hit the Himalayan foothills in recent times.

Dr Rastogi said that the NGRI's seismological observatory recorded the earthquake with its epicentre near Chamoli in the Garhwal Himalayas early this morning.

According to the NGRI, the earthquake measured 6.5 on the Richter scale. The Indian meteorological department observatory, however, has put it at 6.8.

Chamoli is about 100 kilometres south-east of Uttarkashi which was struck by a major earthquake on October 20, 1991. Measuring 6.5 on the Richter scale, it had claimed around 2,000 lives.

"We do not know about the casualties. Since Chamoli has thickly populated areas with some big towns, the toll could be more," said Dr Rastogi.

"We do not know if any landslides were triggered by the quake. Normally, landslides occur simultaneously with a quake,'' he said.

As for the Tehri dam, which is located 100 kilometres south-west of the present earthquake's epicentre, the expert foresaw no danger to the structure. ''It is quite well designed and nothing may happen even if bigger quakes hit the region," he said.

According to him, there has been a lot of seismic activity in the region. In the last eight years, 11 earthquakes of the magnitude of six on the Richter scale have occurred in this region. Forty major earthquakes have been recorded in the region in the last 100 years.

The Himalayan region has also witnessed four 'great' (with the magnitude of 7 to 7.9 on the Richter scale) earthquakes in the last 102 years. These are: in the Assam-Meghalaya plateau in 1897, the Kanga region in 1904, the Bihar-Nepal area in 1934 and the North-East, along the Sino-Indian border, in 1950.

There is no doubt that it is the most sensitive seismic zone, with minor tremors occurring all the time in the region. ''As the northern movement of the Indian Plate subducts at the rate of two centimetres per year, the Himalayas have been rising by one centimetre annually. The quakes occur along the subducting surface. The damage occurs in a wider area and is not confined to a small circle around the epicentre.

''For instance, in the case of the Latur earthquake which occurred on September 30, 1993, major damage was confined to a 15-kilometre radius since it was a shallow quake -- 2.8 km deep. About 10,000 people died in that quake. But in the case of quakes in the Himalayan region, the damage is normally spread over a 100-kilometre radius as these quakes have depths of 10 to 20 kilometres.''

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