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April 28, 2015

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Capital may have moved 3 meters south

THE earthquake which struck Nepal on Saturday may have caused a land area around the capital Kathmandu to budge by several meters, experts say.

Kathmandu moved possibly about three meters south, according to initial analysis of seismological data obtained from sound waves which travel through Earth after an earthquake, said University of Cambridge tectonics expert James Jackson.

An area about 150 kilometers long and 50 kilometers wide in a fault running underneath the Kathmandu valley gave in after decades of pressure, causing rocks on top of the fault to slip south over the rock underneath.

The fault lies between two tectonic plates — one bearing India pushing north into a plate carrying Europe and Asia at a rate of about two centimeters a year — the process that created the Himalayas in the first place.

Saturday’s lurch likely saw the Kathmandu region rise by about half a meter, while the area to its north sank by about the same margin.

Mount Everest was likely too far east to have been affected.

The shifts may be large enough to necessitate adjustments to high-precision world maps.

Japan’s 2011 Tohoku earthquake saw undersea plate movements of about 50 meters, said Paul Tapponnier from Singapore’s Earth Observatory, with large land shifts along the shoreline too.

The largest earthquake in the Himalayas hit Assam in 1950, displacing portions of land by almost 30 meters.

The latest quake had a magnitude of 7.9, much less violent than the 8.2-8.5 typical for the area, said Tapponnier, and likely not strong enough to have relieved all the stress accumulated along the fault.

One thing the experts agree on, is that there will be more major quakes in the stricken region. What nobody knows, is when.




 

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