‘Darwin Gap’ quake may shake Chile once again

LONDON - A fault line in Chile that shook Charles Darwin during his voyages in 1835, and ripped again last year, may strike again.

An analysis of land movement has shown that the magnitude 8.8 quake that hit in February 2010, claiming over 500 lives, increased stress significantly in a segment of a fault which last ruptured in 1835, reports New Scientist.

The 1835 quake coincided with Darwin’s visit to the area. He recorded it in The Voyage of the Beagle, and suggested - nearly 80 years before continental drift was first proposed - that mountains were created by a succession of small events, rather than in one explosive event.

Stefano Lorito of the National Institute of Geophysics and Volcanology in Rome, Italy, and colleagues have now used tsunami, GPS and radar data to assess the amount of land movement during last year’s quake.

By feeding this into a model, they were able to estimate the amount of slippage on the fault and the variation in the release and accumulation of stress along it.

They found that the fault slipped by up to 19 metres along a segment north of the epicentre, close to the city of Constitucion, which in 1928 was hit by a magnitude 8 earthquake.

Further south they recorded a secondary concentration of slip, measuring up to 10 metres. This slip happened near the epicentre of a magnitude 9.5 earthquake that shook Chile in 1960.

In both these regions, the large movement appears to have released a lot of pent-up stress.

Worryingly, on the central segment of the fault - dubbed the ‘Darwin Gap’ because it was responsible for the magnitude 8.5 earthquake that Darwin experienced - the slip in last year’s quake was far smaller, at less than 5 metres.

This part of the fault appears to have accumulated more stress since then, raising the likelihood of another big quake of magnitude 7 to 8. (ANI)