CHANDIGARH—Wave of tremors in North India recently increased the level of fear and concern about impending danger. “Earthquakes represent the next tectonic event,” says Dr. Ritesh Arya, Guinness World Record holder and internationally renowned Geologist of Kasauli. He said hill stations near Chandigarh are geological upside down hence north India prone to seismic activity.
Based on his findings, he said that towns like Shimla, Solan, Parwanoo and Surajpur axis located near Chandigarh and two neighboring States. It is geologically upside down means that older rocks were resting on the younger rocks as a result the entire sequence is geologically very fragile, he says and adds susceptible to greater damage in the event of epicenter being concentrated on these zones.
Surajpur region is located on the Surajpur Thrust where the Tethyan Himalayan Limestone sequence is resting over the younger Shivalik formation. Lower Shivalik formation (15 million years old) comprises sandstone and shale representing a freshwater terrestrial environment. It is overlain by Subathu limestone and black carboniferous (approx 55 million years old) represents the marine environment at the time deposition.
“This gap in the depositional history is the matter of concern and is also the cause of concentration of seismic activity in the region,” says Dr. Arya. Dwelling on his study, he said that in Barog or Solan, the Subathu formation, around 55 million years old was being overlain or thrust by Krol Formation which was more than 400 million years old. On the other, the metamorphosed Shimla slates are overlying the younger sedimentary tertiary sequence of Subathu, says he.
Presently, these areas have been crowded epicenters with tourism, education institutes and industries coupled with high rise buildings in absence of proper geotechnical institutions to control and design the buildings which is of paramount importance to withstand the seismic activity. “The whole concept o sustainable development goes for a six in the area,” said Dr. Arya.
Commenting on the reason of frequent tremors recently, he said that there was a tectonic shift of the Indian Plate at a rate of 47 millimeters a year towards Chinese Plate. Geologically, the region is highly folded and faulted due to the northward tectonic movement of Indian Plate which dragged for millions of years to finally collide with Chinese Plate.
He stressed on the need of setting up of geotechnical institute and monitor data collected from the bore wells to seriously study and reinterpret data for predicting earthquakes and to minimize the damage. He revealed that during the earthquake at Latur it was found a surge in the level of groundwater several hours before the event occurred. He observed that the water level either increased or decreased sharply before a tremor hits an area. Besides, its chemical composition is also altered due to an increase in Radon gases because of excessive radioactivity before and after the event.
Of the earthquake-prone areas in the country, 12 percent is prone to very severe earthquakes, 18 percent falls under severe earthquakes and 25 percent to the damageable earthquake.
From 1819 to 1950, an earthquake of 8 magnitudes at Richter Scales occurred in Kutch (Gujarat), Kangra (Himachal Pradesh); an earthquake of 8.3 magnitudes occurred on Bihar-Nepal Boarder; 8.5 magnitudes at Richter Scale in Arunachal Pradesh. Since 1950 the country had experienced an earthquake of fewer than 6.5 magnitudes at Richter Scales.
By Y.S. RANA :