For Indian seismologists it has never been a question of whether but when. Ever since the sub-sea Sumatran quake that triggered a tsunami in December 2004, they have warned that the Indian plate has become seismically very active and needs close tracking. The Indian plate is one of the 14 major plates that are locked on to the surface of the earth like a jigsaw puzzle. And when these rigid plates nudge one another, the accumulated stress which is built up along the boundaries is released to trigger an earthquake. They may be adept at explaining how and why earthquake happens, but seismologists, even after decades of painstaking study, are still in the dark about when or where exactly it will strike or how severe it will be. What they know for sure is that the frequency of earthquakes along the Indian plate has increased and this trend could continue. At times scientists stick their neck out to forewarn-like they did after the tsunami-about abnormal seismic activity in north-east India and the Himalayan region. However, in a study published in the journal Science in 2001, specialists from the University of Colorado, US, and the Indian Institute of Astrophysics in Bangalore, who studied seismic data in the Himalayan region, concluded that a major earthquake was overdue. They estimated that two major quakes, with a magnitude of 8.1-8.3, could strike at any moment. Worse, the big ones coming are expected to cause havoc in highly populated areas in the subcontinent, putting an estimated five crore people at risk. Among the cities in the line of threat are Delhi, Kolkata, Lucknow, Islamabad, Kathmandu, Dhakha and Thimphu. The October 8 earthquake lies along the fault line where the Indian and the Eurasian tectonic plates collide, pushing up the Himalayan mountain range. The Indian plate drives northwards at a rate of a few centimetres every year, moving under the Eurasian plate and creating a zone that is prone to seismic activity. To that extent, the Kashmir earthquake fitted in with the scientists predictions. But thankfully, it was relatively weak. The effects of the earthquake were lessened because it emerged 10 km below the earths surface, says seismologist Janardhan G. Negi, director-general, Madhya Pradesh Council for Science and Technology. However, aftershocks could trouble the area for a few more months. American geologists Roger Bilham and Kali Wallace of the University of Colorado point out that the Himalayan region-from the eastern Indian plate boundary in Myanmar to the western boundary through Pakistan and Afghanistan-has a dozen regions that could experience a future earthquake with a magnitude more than 8. Since the population of the Ganga basin is greater than at any time in history, they say that any massive earthquake in the future could affect people more than last years tsunami did. Generally, Indian geologists are restrained when it comes to issuing a caution or an earthquake warning. The exception is a 10-member group led by Harsh K. Gupta, former director of the National Geophysical Research Institute, Hyderabad, which has alerted that an earthquake with a magnitude of 5 could hit Koyna in Maharashtra in the next few weeks. Privately though, some of them are apprehensive about a big one striking in the region between Himachal Pradesh and Assam in the next 10 years. But they do not rule out smaller ones. As the number of people displaced by the Kashmir quake rises to 25 lakh, seismologists are also concerned about the construction of buildings. In Kashmir, most buildings were too weak to withstand earthquakes. In the absence of accurate predictions regarding quakes, the only option for urban India, where construction continues to be haphazard, is to ensure that structures are built to resist substantial tremors. In metros and elsewhere, old buildings made of brick and mortar, could cave in if there is a serious quake. Architects point out that reinforced concrete filled in with brickwork provides very little resistance to lateral forces like those triggered by a quake. It is only the use of better quality steel and a strict adherence to safety regulations based on the study of soil that can prevent a collapse.
Posted on: Wed, 08 Oct 2014 01:13:01 +0000