Is Uttarakhand ready for a mega-quake?

Is Uttarakhand ready for a mega-quake?

Growing concern over the possibility of a major earthquake hitting the central Himalayan region, which includes Uttarakhand state, is being expressed time and again during deliberations among geologists and seismologists. They believe that a mega-quake, measuring above magnitude 8 on the Richter scale, might jolt the region any time, leading to unprecedented damage to life and property. 

Seismologists studying the neo-tectonic activities in the central Himalayas ascribe the phenomenon of increased tremors to the gradual movement of the Asian plate towards the Eurasian plate. Scientists at Wadia Institute of Himalayan Geology (WIHG) in Dehra Dun, put the rate of this gradual plate movement at 14 millimetres per year. They attribute the rise of the Himalayas to continental collision of the underground tectonic plates.

Scientists feel that it has been a long time since the last high-intensity quake struck the region and a big one may be due, arguing that due to the ongoing intense seismic activity, a sudden release of accumulated trapped energy within the tectonic plates might take place at any time. This trapped energy is waiting to burst out in the form of an earthquake. Among others, Dr RK Chadda, a scientist with the National Geographical Research Institute, opines that this intense seismic activity could last until 2020.    

Brain-storming sessions and seminars have focused on this phenomenon. The WIHG has installed a seismic network across the Garhwal region to monitor underground tremors while scientists at the Central HNB Garhwal University are monitoring changes in the course of major rivers flowing through the mountains. This phenomenon of change of course due to neo-tectonic activity was noticed by scientists, particularly with regard to the Alaknanda river. In fact, they are also studying increasing incidence of multiple landslides in the area. Of course, there are   many theories regarding the phenomenon and the impact of neo-tectonic activity on lower Himalayan quakes.

Even though this view about the prospects of a major earthquake hitting Uttarakhand, particularly the Garhwal mountains, has gradually gained currency, yet another view, though contrary, has emerged, which rules out such a possibility. Quoting a well-known Japanese geophysicist, Jim Mori, a top WIHG scientist, Dr Sushil Kumar, maintains that fears about the sudden outburst of enormous accumulated energy trapped under the tectonic plates for decades now, have been allayed by Dr Mori’s research. He says that Dr Mori has opined that the   trapped energy does not stay under pressure for long and, as such, gets released gradually over a period of time. So, according to Dr Kumar, the trapped energy under the central Himalayan tectonic plates, might have got released over the past few decades, therefore no more posing the threat of a sudden outburst in the form of a big quake.  

Falling in zone 4 and 5 of the seismic map of the country, Uttarakhand state and its geographically contiguous areas, have been experiencing major and minor earthquakes at regular intervals. Some of these occurred in the years 1803, 1816, 1905, 1926, 1927, 1945, 1958, 1966, 1991 and 1999, most of these being below the magnitude 7 on the Richter scale. Geographically contagious Nepal in the east and Himachal Pradesh in the west lie in a similar sensitive belt and have faced big jolts.

 Two recent quakes that hit the Garhwal Himalayas in 1991 and 1999 were below magnitude 8 on the Richter scale, yet they caused enormous damage to life and property. Some 1,500 people were killed, and hundreds rendered homeless, in the 1991 earthquake that jolted Tehri, Chamoli and Pauri districts of the state. Four quakes in the central Himalayan belt and below are said to have been above magnitude 8. These included the ones that hit Nepal in 1950 and 2015 and parts of Bihar near Nepal in 1934.   

The impact of the central Himalayan earthquakes is also felt in areas that are not located faraway geographically and which fall in zone 4 of the seismic map. Thus, national capital New Delhi and some other cities and towns feel the impact of these quakes substantially. Sometimes, a quake occurring even in a remote part of Afghanistan unsettles parts of north India. One such quake, which measured magnitude 6.8 on the Richter scale, jolted Delhi recently.

Experts fear that a quake of magnitude 7 or above could wipe out a substantial portion of Delhi’s population. Even though areas falling in zone 3 and 4, namely parts of some southern and central states of the country, are relatively less vulnerable to quakes, yet the possibility of a quake hitting these states cannot be ruled out.    

As per the country’s seismic map, while Uttarakhand, Kashmir, Himachal Pradesh, Rann of Kutch, a part of north Bihar and the Andaman and Nicobar Islands lie in zone 5, some southern and central Indian states lie in the least-sensitive zone 2 or 3.

(The writer is a senior journalist based in Dehradun)

 

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Is Uttarakhand ready for a mega-quake?

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