Risks of another Nepal earth­quake re­main high, ac­cord­ing to re­searchers

The China Post - - INTERNATIONAL -

Large quakes in Nepal this year only par­tially re­lieved stress on a ma­jor Hi­malayan fault line, and chances for a big tremor are as high as be­fore, re­searchers said Thurs­day.

Jean- Philippe Avouac of the Univer­sity of Cam­bridge, who coau­thored stud­ies pub­lished si­mul­ta­ne­ously in the jour­nals Na­ture Geo­science and Science, said there was enough “strain avail­able to drive a large earth­quake in western Nepal.”

“This was the case be­fore the Gorkha earth­quake and it hasn’t changed sig­nif­i­cantly with the Gorkha earth­quake,” he told AFP by email, adding the risk for another quake was “defini­tively not lower” — though also not sig­nif­i­cantly higher.

The Gorkha dis­trict was near the epi­cen­ter of a 7.8-mag­ni­tude tremor on April 25, the worst in Nepal in more than 80 years, fol­lowed on May 12 by a 7.3-strong after­shock.

The twin quakes killed more than 8,700 peo­ple, trig­gered land­slides and de­stroyed half a mil­lion homes, leav­ing thou­sands in need of food, clean wa­ter and shel­ter.

Nepal

rests on a ma­jor

fault line be­tween two tec­tonic plates — one which bears In­dia push­ing north and east at a rate of about two cen­time­ters (0.8 inches) per year against the other, which car­ries Europe and Asia.

This process along the Main Hi­malayan Thrust fault ( MHT) is what cre­ated the Hi­malaya moun­tain range, and causes earth­quakes when strain built up along the fault gives way pe­ri­od­i­cally, thrust­ing the over­ly­ing land­mass up and out­ward.

In the re­cent dis­as­ter, an area some 150 kilo­me­ters (93 miles) long and 50 kilo­me­ters wide gave in af­ter decades of pres­sure.

Ex­perts cal­cu­lated that the cap­i­tal Kathmandu shifted more than 1.5 me­ters (nearly five feet) south­wards, and was raised by nearly a me­ter. Mount Ever­est was es­ti­mated to have moved three cen­time­ters to the south­west.

The April 25 quake started north­west of Kathmandu, and prop­a­gated east­ward along the fault for about 140 kilo­me­ters, run­ning un­der­neath the city but not reach­ing the land sur­face. The pres­sure “un­zipped” another “few tens of kilo­me­ters east” in the after­shock.

The f ault had re­mained “locked” for 20 years with­out any re­lease of stress, said the Na­ture Geo­science pa­per.

And the 2015 quakes trans­ferred un­re­leased pres­sure into western and shal­lower parts of the Earth’s crust.

“The locked por­tion of the MHT west of the 2015 event calls for spe­cial at­ten­tion,” it cau­tioned — not­ing a 800-kilo­me­ter-long stretch where there had been no large quake for over 500 years.

Avouac added: “We will have at some point a large earth­quake in western Nepal, but the prob­a­bil­ity of it hap­pen­ing to­day is not sig­nif­i­cantly larger than it was be­fore the Gorkha quake.”

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