Experts don't rule out many aftershocks; Minister appeals not to panic

NEW DELHI: A day after facing devastating earthquake, Nepal and northern Indian states on Sunday felt an intense aftershock of 6.9 magnitude with its epicentre 75 km east of Kathmandu which may well be taken as yet another tremor of moderate intensity. Though its impact was not like what the region felt on Saturday, it was the most severe of all 35 aftershocks reported in the region in the past over 24 hours.
The entire region in any case continues to stare at a grim situation not only due to the possibility of few more aftershocks of varied magnitude but also due to prediction of heavy rains and thunderstorms in Nepal, eastern Uttar Pradesh, northern Bihar and sub-Himalayan Sikkim and West Bengal in next 24 to 72 hours which may affect the ongoing relief works.
Referring to the Sunday's seismic event, Harsh Gupta, president of the Geological Society of India, said, "It was an aftershock. India and Nepal may face many such aftershocks. There had been instances in the past when the country had faced hundreds or even thousands of aftershocks after the main earthquake".
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Gupta, former director of the Hyderabad-based National Geophysical Research Institute, told the TOI that one should not get panic of the reports of aftershocks.
"It's quite natural after the main earthquake. These aftershocks are also earthquakes. Since it happen after the main seismic event of bigger magnitude (earthquake), we call it aftershocks", he said, citing an example of an earthquake of 8.7 magnitude that had occurred in 1950 along India-China border whose aftershocks were felt till 1954 with one of the aftershock of the magnitude of 8 felt even two years after the main seismic event.
The IMD and ministry of earth science too came out with details of aftershocks including the one felt on Sunday afternoon.
"The last of the aftershocks was reported at 12.39 PM on Sunday. It was the most sever one of all aftershocks so far at 6.9 magnitude. Others (34) are of magnitude of over 4.0", said the ministry of earth science in a statement without denying the possibility of any other aftershock in coming days.
Union earth science minister Harsh Vardhan, however, advised people to keep calm and appealed others not to spread rumours.
Urging people to believe in reports based on only government advisories on earthquakes, he said, "The Indian Meteorological Department (IMD) has been regularly monitoring the seismic activity in the region and issuing regular reports and advisories from time to time".
The advisories may, however, be in nature of dos and don'ts during and after the earthquakes as technically the tremors cannot be predicted. The IMD's guideline on prediction of earthquakes clearly say, "No scientific technique is available anywhere in the world so far to predict the occurrence of earthquakes with reasonable degree of accuracy with regard to space, time and magnitude".
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The country's national weather forecaster is, however, quite precise about occurrence of rains and thundershower in the region. It in its latest prediction on Sunday evening said, "The activity (rain) is most likely to become widespread on April 27 and 28 with possibility of isolated heavy thunderstorm, particularly over eastern part of Nepal. Similar weather is also predicted for Kathmandu.
"It has been suggested that precaution be taken against the above weather and also due to possibility of landslides at vulnerable sites".
The IMD also predicted that the Sub-Himalayan West Bengal & Sikkim would also experience fairly widespread rain/thundershower activity during next three days with possibility of isolated heavy thunderstorm.
"Scattered thunderstorm activity over Bihar and over East Uttar Pradesh would also occur during next 2-3 days", said the IMD.
As far as aftershocks are concerned, Nepal witnessed as many as 26 of such seismic events on Saturday and nine on Sunday. The last one was felt in many parts of India as well including Delhi, UP, Bihar, Sikkim and West Bengal.
"These aftershocks may come for months, or years. It cannot be predicted", said J L Gautam, head (operations) of Centre for Seismology at IMD while emphasising on need to remain alert and follow certain dos and don'ts during and after the earthquakes.
Talking about country's vulnerability, the director general of the IMD L S Rathore said, "The episode which is happening now is a resettlement of the Indian and Eurasian tectonic plates".
The vulnerability of any region is the degree of damage caused by various levels of movements inside the earth. It may be calculated in a probabilistic way for a single structure or group of structures.
The Bureau of Indian Standards, based on various scientific inputs from a number of agencies, has grouped the country into four seismic zones -- Zone - II, III, IV and V. Of these, Zone V is the most seismically active region while Zone II is the least.
Broadly, Zone -V comprises of entire northeastern India, parts of Jammu and Kashmir and Himachal Pradesh, Uttarakhand, Rann of Kutch in Gujarat, part of north Bihar and Andaman & Nicobar Islands.
The Zone- IV covers remaining parts of Jammu and Kashmir and Himachal Pradesh, Delhi, Sikkim, northern parts of UP, Bihar and West Bengal, parts of Gujarat, small parts of Maharashtra near the west coast and Rajasthan.
The Zone III comprises of Kerala Goa, Lakshadweep, remaining parts of UP, Gujarat and WB, parts of Punjab, Madhya Pradesh, Jharkhand, Chhattisgarh, Maharashtra, Odisha, Telangana, TN, AP and Karnataka.
The Zone-II covers remaining parts of the country.