Second Nepali earthquake part of chain reaction in seismic hotspot

The 7.3-magnitude earthquake that struck Nepal yesterday, 17 days after a lethal 7.8 quake, is part of a chain reaction in a notorious seismic hotspot, say scientists.

Like buttons popping off one by one from a shirt that is ripped open, a large quake 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, a not-for-profit organisation based in London. "It is a chain reaction."

Yesterday's quake hit 76km 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.