Rajendra Prasad Nailwal –
The devastating earthquake in Nepal, which has so far claimed over 7000 lives, injured and left hundreds of thousands of people homeless has serious implications for the adjoining sub-Himalayan state of Uttarakhand.
Uttarakhand has also been experiencing big jolts all along the past 100years, among the worst of which occurred in 1934, 1950, 1991 and 1998.
According to earthquake scientists, Uttarakhand and Nepal fall within the seismically active seismic gap extending from Nepal to Dehra Dun.
The 1991 and 1998 quakes wreaked havoc in the high altitude districts of Uttarkashi and Chamoli killing more than 1500 people and uprooting hundreds of others.
The Frequency
Wadia Institute of Himalayan Geology (WIHG) scientists say that a great detachment underlying the sedimentary and metamorphic cover of Himalayas, which raptures from time to time, leads to great quakes in the region.
A study conducted by them showed that two sub Himalayan earthquakes in 1255 and 1934 had badly ruptured the surface of the earth. According to them, four major quakes measuring above seven on Richter scale had caused great loss of life and property.
Seismologists observed that big tremors have a periodic pattern dependent on the tectonic stress in an area. If a big quake above 7 on the Richter scale hits a particular area, it is not likely to repeat anytime soon.
If however, a seismically active zone has not experienced a big quake for long time, the possibility of the same area being jolted by a big quake cannot be ruled out.
Seismic gap
Records on genesis of the quake occurrences in the Central Himalayan region quote two known geologists Kailash Nath Khatrri and Roger Bilham of University of Colorado as identifying a ‘seismic gap’ between Kathmandu in Nepal and Dehra Dun, capital of Uttarakhand state.
Interestingly, Bilham had predicted in 2001 that a big quake above 8 on Richter scale occurring along the seismic gap of the central Himalayan region was likely.
He reiterated that even if smaller quakes release tectonic stress to some extent, there was high possibility of accumulated tectonic stress leading to huge earthquakes.
Accurate forecast
Corroborating these findings soon after the major earthquake that shook Garhwal region of Uttarakhand in 1991 and 1998, Dr V C Thakur, the then director of WIHG Thakur had said that there were inherent similarities in the source processes of these quakes, which point to their occurrence on the sub-horizontal plate boundary fault.
Professor Khattri had also stated at that time that a uniform type of deformation exists in the Himalayan region at least for the occurrence of the great quakes.
According to him, thrust type earthquake hypo centres define the plate boundary and sense of slip on it.
Hence, earthquakes could occur in the future.
Fundamental fracture
Dr Devendra Pal, a former WIHG scientist, propounded a similar theory on lower Himalayan tectonic activity. In 1992, he said that major fundamental fracture divides could occur in Eastern and Western Himalayas.
While Himachal Pradesh and Jammu and Kashmir are likely to be affected in the West, Garhwal and Kumoun in Uttarakhand and adjoining Nepal in the East could be the victims.
The entire area has been put in Zone Four to Five on the Richter scale in the earthquake hazard zone map of India.
The Ridge
Calling it a Ridge, Dr Pal said that the structures of Eastern and Western parts of the ridge are very different and that the ridge originates in Carlberg in the Indian Ocean.
Early records of various conferences on lower Himalayan seismicity at WIHG underline the fact that Himalayan front is vulnerable to major earthquakes.
Oregon State University Scientist Robert Yeast had said at a conference held about 15 years ago that the Himalayan region was likely to experience severe tremors.
The only thing that could be done now to minimise the impact of a quake is to learn a proper lesson from the Nepal earthquake and revisit the country’s preparedness to face such a calamity and minimise loss to life and property.
Rajendra Prasad Nailwal is a retired Special Principal Correspondent of the Times of India. He now lives in Dehra Dun.
Photo:
Nepalese victims of the earthquake search for their belongings among debris of their homes in Bhaktapur, Nepal, on April 29, 2015 (David Ramos-Getty Images)
