AFP
Paris
The fresh earthquake that struck Nepal yesterday, 17 days after a lethal 7.9 temblor, is part of a chain reaction in a seismic hotspot, scientists 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 chain reaction.”
“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 5 magnitude.
Over 80 years prior to yesterday’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 tectonic plates in this region has significantly eased,” Bernard said.
At the interface of the two plates, the Indian plate is riding upwards at around 2cm (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.