Kathmandu raised by a metre, Everest has sunk by an inch

  • Zia Haq, Hindustan Times, New Delhi
  • Updated: May 02, 2015 01:37 IST

Scientists from a specialist study wing of the European Space Agency, among others, have constructed the first geological portrait of quake-hit Nepal to discover some earth-shattering changes — the Kathmandu valley has risen by up to a metre, while the Everest sunk by one inch and areas north have settled below their original height.

Perched precariously on the boundary of two colliding continental plates, Nepal and northern India’s “geological profile” may have undergone permanent changes, preliminary analysis suggests. The study was made possible by a special satellite passing over the devastated country several times since the big quake.

The experts used images from Europe’s Sentinel-1a satellite — the first of a new-generation spacecrafts capable of picking up ground movement — to produce an interferogram, a multi-coloured graphic representation, which is like an MRI scan of the human body.

The experts concluded that an area of 120km by 50km around Kathmandu was lifted by the quake up to 1 metre. “Unwrapped interferogram shows clearly uplift around Kathmandu and subsidence to the north,” Tim Wright of Leeds University who analysed the data, said in a comment via Twitter.

Using the same radar images, UNAVCO, a nonprofit geoscience research consortium, inferred that some of the world’s tallest peaks — including Mount Everest — dropped by about 1 inch (2.5 cm), probably because the land beneath loosened up, as built-up strain got released. That possibly triggered the deadly base-camp avalanche.

Wright and others used a mathematical model to add up the number of brightly coloured fringes on the interferogram. They counted 34 fringes, which correspond to an elevation of one metre, with each “fringe” denoting a vertical movement of about an inch.

The magnitude 7.9 earthquake released stresses building up for over 100 years, according to estimates.

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