Second quake part of chain reaction: scientists

May 12, 2015

The 7.3-magnitude earthquake that struck Nepal on Tuesday, 17 days after a lethal 7.8 temblor, is part of a chain reaction in a notorious seismic hotspot, scientists said.

Like buttons popping off one by one from a shirt that is ripped open, a large displaces stress to another part of a fault, causing it to rupture, they said.

"Large earthquakes are often followed by other quakes, sometimes as large as the initial one," said Carmen Solana, a volcanologist at Britain's University of Portsmouth.

"This is because the movement produced by the first quake adds extra stress on other faults and destabilises them," she told the Science Media Centre (SMC), a not-for-profit organisation based in London.

"It is a ."

Tuesday's quake hit 76 kilometres (47 miles) east of the Nepalese capital Kathmandu, followed around half an hour later by a second tremor of 6.3 magnitude.

The April 25 quake, which killed more than 8,000 people, occurred a similar distance west of Kathmandu.

Both events happened on the same fault, where the Indian and Eurasian plates of the Earth's crust meet, bumping and jostling.

"Since the first earthquake in April, aftershocks have been migrating more or less southeastwards," Nigel Harris, a professor of tectonics at Britain's Open University, told the SMC.

"There has been a rip in the underlying plate which has suddenly moved west to east, and this second earthquake is an extension of that process."

The April 25 and May 12 quakes were shallow, which means that ground shaking is far greater than with temblors that occur at depth, the scientists said.

Pascal Bernard, a seismologist at the Institute for Planetary Physics in Paris, said aftershocks in the region were unlikely to be greater than five magnitude.

Over 80 years prior to Tuesday's quake, eastern Nepal had an 8.1 temblor in 1934. Around 10,700 people were killed in Nepal and neighbouring India.

"This means that pressure between the two in this region has significantly eased," Bernard told AFP.

At the interface of the two plates, the Indian plate is riding upwards at around two centimetres (fourth-fifths of an inch) a year.

The movement is not smooth but rather laden with friction, leading to sharp and potentially destructive jolts as stress builds up.

"The boundary region of the India and Eurasia plates has a history of large and great earthquakes," the US Geological Survey (USGS) said on its website.

"Prior to April 25, four events of magnitude six or larger had occurred within 250 km of this area over the past century."

Explore further: Why the Nepalese quake was so destructive

Related Stories

Why the Nepalese quake was so destructive

April 28, 2015

The earthquake, which wreaked havoc in the Kathmandu Valley of Nepal on Saturday about noon local time, was the strongest quake in the world so far this year. With a magnitude of 7.8 it was felt over a very large area from ...

Did Kathmandu shift? Questions and Answers

April 27, 2015

The tremor which struck Nepal on Saturday, killing more than 3,500 people, may have caused a land area around the capital Kathmandu to budge by several metres, experts say.

Recommended for you

Greenland ice loss quickening

December 7, 2018

Using a 25-year record of ESA satellite data, recent research shows that the pace at which Greenland is losing ice is getting faster.

New study explains creation of deadly California 'firenado'

December 6, 2018

A rare fire tornado that raged during this summer's deadly Carr Fire in Northern California was created by a combination of scorching weather, erratic winds and an ice-topped cloud that towered miles into the atmosphere, ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.