Seimologists say risk of Chile quake high

VALPARAISO, Chile, Jan. 31 (UPI) -- The 8.8-magnitude earthquake in Chile in February 2010 did not relieve seismic stress as expected and earthquake risk remains high in the area, researchers say.

Geophysicist Stefano Lorito of Italy's National Institute of Geophysics and Volcanology in Rome and colleagues say the risk of a large seismic event might even be higher in some places than it was before last year's quake, ScienceNews.org reported Monday.

The stress remains, they report in an article in the journal Nature Geoscience, because instead of the ground moving where stress had been building the longest, the greatest slip took place where a different quake had already relieved stress just eight decades earlier.

Chile is subject to powerful earthquakes. The largest temblor ever recorded in the world, at a magnitude of 9.5, occurred on Chile's coast in 1960. A magnitude-8.0 quake struck in 1928 180 miles north of that quake.

Between those two locations lies a stretch of coast that hadn't had a major event since 1835, when Charles Darwin visited witnessed a major earthquake, and seismologists believed the "Darwin gap" would be the location of the next major quake -- but it wasn't, researchers say.

The greatest slip in 2010 occurred north of the quake's epicenter, where the 1928 quake struck. South of the epicenter there was another area of slip, but directly between the two, in the Darwin gap, there was little to no movement.

Other earthquake zones, such as in Sumatra in 2007, have experienced big earthquakes that didn't relieve pent-up geologic stress where scientists thought it was greatest, Lorito says.

"It is not strange to see that the rupture is complex, and that some parts can break at one time and some at another time," he says.