Even as the massive tremors shook large parts of Uttar Pradesh, it was the alluvium cover in the Indo-Gangetic Plain, which acted as a cushion and prevented large-scale damage in the State. In geological terms, the State falls in the “safe” zone as the alluvium cover acts a “shock absorber.”
Since the affect of earthquakes is more on the rocky surfaces, as was evident in the 1991 Uttarkashi and the 1995 earthquake in Chamoli (now in Uttarakhand), its impact was not felt much in Uttar Pradesh.
But the intensity of Saturday’s tremors have led experts to rethink on how safe is the State from quakes. There is an opinion which says that the magnitude of the tremors could have left an impact on the rocky surface below the alluvium cover. Many are of the view that tremors of this magnitude perhaps visited Uttar Pradesh for the first time in 80 years. “Though Uttar Pradesh is safe, thanks to the rich alluvium surface which acts as a cushion, the possibility of even the shock absorber being shaken by the magnitude of the tremors cannot be ruled out,” said A.R. Bhattacharya, an eminent earth scientist and an expert in Himalayan Geology.
Professor Bhattacharya said the “faults,” or cracks in the rocky surface below the alluvium cover could have been activated by the magnitude of Saturday’s tremors. The rocky surface below the alluvium cover of the Indo-Gangetic Plain has a thickness of about 2.5 km kilometres and around the Himalayan foothills its thickness increases to around 6 km. The north-western belt seems to have been affected by the high magnitude of the tremors.
Three, or four faults are found in North India — the Purnea Fault in Bihar, the Lucknow Fault in Uttar Pradesh and the Moradabad Fault, also in U.P. Uttar Pradesh. “There is the Delhi-Hardwar Fault which meets the Aravallis in Rajasthan,” Dr. Bhattacharya told The Hindu .
