Press Esc to close
Tuesday 02 September 2014
News updated at 12:18 PM IST
Weather
Max: 27°C
Min : 20°C
In Bangalore
Generally cloudy

Tehri dam sitting on an active fault: seismologists

Hyderabad, Dec 9, 2012 (IANS)

There is an active fault beneath the Tehri dam that enhances the earthquake risk, scientists of the National Geophysical Research Institute (NGRI) here have  reported. The Tehri dam  is located near Tehri town in Uttarakhand in the Kumaon-Garhwal Himalayas region.

"The tectonic loading on this active  fault due to local seismicity, coupled with the reservoir loading and unloading, may generate earthquake(s) and cause additional seismic risk in this critically stressed region," Sandeep Gupta and co-workers in NGRI claim in their report in the latest issue of  "Current Science" published by the Indian Academy of Sciences.

They say their conclusion is based on  evidence obtained by  mapping of the seismicity pattern in the Kumaon-Garhwal Himalayas region in general and around the Tehri  dam in particular, using observations from a temporary seismological network  they operated for over 39 months during 2005-2008.  During this period, over 20 earthquakes of magnitude 1.6-2.8 on the Richter scale were recorded in a 20-km radius of the dam site.


According to the scientists, the dam site was chosen in 1961, "at the time when the plate tectonics theory was taking birth and researchers were not well-educated with the fundamental mechanism responsible for earthquakes in the Himalayas. Since then, much has changed in the context of our theoretical understanding and observations related to the evolution of the Himalaya and the associated earthquake hazards".

The Tehri dam falls in a region of possible future great earthquakes, the researchers say. The last major earthquake of magnitude 7.7 occurred 209 years ago, in 1803, close to Srinagar-Garhwal.  Many intermittent earthquakes including the 1991 Uttarkashi earthquake (magnitude 6.8) have rocked the region and released parts of energy stored elastically due to the movement of the Indian plate.

"Still, a large amount of residual stress has to be released by an earthquake of magnitude possibly not less than 8," the NGRI scientists claim.  They say that geodetic levelling observations in the region also suggest the possibility of great earthquakes to release the recoverable elastic strain stored in the upper crust of the outer Himalayas in this part of the Himalayas.

According to the NGRI team, the Tehri dam was initially designed to withstand  ground acceleration expected from the maximum credible earthquake of magnitude 7.2, whereas the ground acceleration would be twice this if an earthquake like the 1905 Kangra temblor strikes again.

The scientists have also studied the seismicity around the dam in relation to reservoir filing.  They observed an increase in seismicity from December 2005 onwards, after its first filling in October 2005. "We, thus, speculate that seismicity in the vicinity of the Tehri dam may have a linkage with instability created by loading and unloading of the reservoir."

This, coupled with the close proximity of the seismically active fault to the dam, has  serious implications for the earthquake hazard scenario and  calls for "re-assessment, analysis and further examination of our results using dedicated ground and space-based seismic and geodetic networks," the scientists concluded.

Go to Top

Photo Gallery
President Pranab Mukherjee grants degree to a student at the 14th convocation of the University...

President Pranab Mukherjee grants degree to a student at the 14th convocation of the University...

Fireworks on the occasion of 410th installation anniversary of Sri Guru Granth Sahib, the holy...

Fireworks on the occasion of 410th installation anniversary of Sri Guru Granth Sahib, the holy...

Left Front activists take part in a rally to observe anti-imperialist day in Kolkata on...

Left Front activists take part in a rally to observe anti-imperialist day in Kolkata on...

Flood water flows through Srisailam dam after its four crest gates were opened in Kurnool on...

Flood water flows through Srisailam dam after its four crest gates were opened in Kurnool on...

BJP president Amit Shah during a visit to Sree Padmanabhaswamy temple in Thiruvananthapuram on...

BJP president Amit Shah during a visit to Sree Padmanabhaswamy temple in Thiruvananthapuram on...

Prime Minister Narendra Modi shakes hands with Japanese Minister of Foreign Affairs Fumio...

Prime Minister Narendra Modi shakes hands with Japanese Minister of Foreign Affairs Fumio...

Actress & BJP MP from Chandigarh Kirron Kher speaks during a seminar on...

Actress & BJP MP from Chandigarh Kirron Kher speaks during a seminar on...

Prime Minister Narendra Modi and Japan's Prime Minister Shinzo Abe makes a toast during a banquet...

Prime Minister Narendra Modi and Japan's Prime Minister Shinzo Abe makes a toast during a banquet...

Congress president Sonia Gandhi prays in a temple during a visit to her constituency Rae Bareli...

Congress president Sonia Gandhi prays in a temple during a visit to her constituency Rae Bareli...

Congress president Sonia Gandhi in a village hut during a visit to her constituency Rae Bareli on...

Congress president Sonia Gandhi in a village hut during a visit to her constituency Rae Bareli on...

Copyright 2014, The Printers (Mysore) Private Ltd., 75, M.G Road, Post Box 5331, Bangalore - 560001
Tel: +91 (80) 25880000 Fax No. +91 (80) 25880523