Press Esc to close
Tuesday 28 June 2016
News updated at 7:57 AM IST
Weather
Max: 27.5°C
Min : 19.4°C
In Bengaluru
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
People carry an effigy representing inflation devil on a camel-cart during a demonstration...

People carry an effigy representing inflation devil on a camel-cart during a demonstration...

A car wades through a water logged lane at Jayadev Bihar after heavy monsoon rains in Bhubaneswar...

A car wades through a water logged lane at Jayadev Bihar after heavy monsoon rains in Bhubaneswar...

A sadhu at a base camp for Amarnath Yatra ahead of their registration in Jammu...

A sadhu at a base camp for Amarnath Yatra ahead of their registration in Jammu...

The titular head of Wodeyar dynasty Yaduveer Krishnadatta Chamaraja Wodeyar and Trishika Kumari...

The titular head of Wodeyar dynasty Yaduveer Krishnadatta Chamaraja Wodeyar and Trishika Kumari...

A white tiger takes bath in a pond during a hot summer day at its enclosure in Kolkata Zoo...

A white tiger takes bath in a pond during a hot summer day at its enclosure in Kolkata Zoo...

An artiste gives finishing touches to an idol of Goddess Durga for upcoming Durga Puja...

An artiste gives finishing touches to an idol of Goddess Durga for upcoming Durga Puja...

Collapsed tents at BJP Awadh Kshetriya Booth Sammelan following the storm, in Barabanki...

Collapsed tents at BJP Awadh Kshetriya Booth Sammelan following the storm, in Barabanki...

Women Kabaddi players who will take part in the Women's Kabaddi Challenge, at a press conference...

Women Kabaddi players who will take part in the Women's Kabaddi Challenge, at a press conference...

People enjoy the rainy weather on a beach along the Arabian Sea in Mumbai...

People enjoy the rainy weather on a beach along the Arabian Sea in Mumbai...

The underconstruction Bogibeel Bridge over the mighty Brahmaputra River in Dibrugarh district....

The underconstruction Bogibeel Bridge over the mighty Brahmaputra River in Dibrugarh district....

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