Science & Environment

Further Chile earthquakes 'possible', say scientists

Earthquake in Chile, 1960
Image caption Chile lies in an earthquake hotspot in the Pacific known as the "ring of fire"

Chilean authorities are working with seismologists in order to prepare for a possible earthquake that could strike the country "any day".

A group of researchers studied the effects of the massive earthquake that jolted the nation in February, killing almost 500 people.

They found that the quake raised the land by as much as 2.5m near the coast and shifted the coastline out to sea.

The findings appeared in the journal Science.

An international team of scientists, led by University of Chile geologist Marcelo Farias, measured land-level changes at 24 sites along the county's coast and in nine estuarine valleys.

They said the 8.8-magnitude earthquake was "the fifth largest event in modern seismology".

Co-author Daniel Melnick, a geologist from Potsdam University, Germany, said seismologists had warned the Chilean authorities about a possible disaster could happen at any given moment - but the state did not act.

"Scientists met with authorities in Talcahuano several months before the earthquake," he told BBC News. "And they warned them that there was a possibility of an earthquake and of a big tsunami.

Image caption Models of the tsunami triggered by the earthquake show waves of up to one metre travelling across the Pacific Ocean

"But the authorities didn't really take the scientists seriously," said Dr Melnick.

The researcher explained that there was often a problem of communication between the scientific community and the local government.

"The authorities believe that if you forecast an earthquake, everybody would start to panic and this would affect the property value," he said.

But a Santiago resident, Enrico, who was just outside the capital during the February disaster thinks people must know an earthquake might strike and be prepared.

"Everyone should know what to do if the ground starts to shake," he told BBC News.

"I was lucky that I was in the countryside when the earthquake happened, but I know that in the city, where lots of people were crammed together in big buildings, there was panic. Nobody knew how to behave."

Exact forecast

Dr Melnick said that the latest study showed that the predictions were correct, and called February's disaster a "wake-up call" for the local authorities.

The team measured the coastal level changes right after the earthquake to calculate the size of the rupture and then determined how much "slip" was released during the shaking.

Slip is the displacement that results when the tectonic oceanic plate jumps back like a spring during an earthquake after years of compressing the continental plate.

Image caption Almost 500 people died in Chile's last earthquake

They found an average slip of 10m - very similar to the forecasted data of 11.9m.

Dr Melnick explained that to predict an earthquake's magnitude, seismologists multiply plate convergence rate by the number of years since the last great event.

"There was an earthquake in south-central Chile in 1835 and it was well documented by FitzRoy and Darwin, [with the data of] land level changes and a tsunami that followed.

"So that means that if we know that a region has not experienced an earthquake in 175 years, then we can say that there is about 11m of slip ready to be released. This way you can estimate the magnitude. And that's very important to know to prepare for it," said Dr Melnick.

Getting ready

He said that using the same method, scientists determined another area that was "ready" for a potentially devastating shaking - northern Chile, close to the border with Peru.

"The region hasn't ruptured since 1877. We can estimate that it is ready for another magnitude 8 or 8.5 earthquake any day - it could happen tomorrow or it could happen in the years to come," he said.

ONEMI, the Chilean National Emergency Office, has been in close contact with the seismologists, trying to prepare for a future earthquake that could strike anytime.

A spokeswoman told BBC News that the agency was working with the local authorities, explaining what should be done if the ground started to shake.

"Earthquakes are our reality. To get the population ready, we have regular risk exercises when people must evacuate the building in a case of an earthquake.

"We educate them, explaining that as soon as they know that the quake is big enough to generate a tsunami, they must go to highlands."

Dr Melnick said it was important that the authorities were finally starting to take science more seriously.

"Local inhabitants know that there could be an earthquake," he said.

"It is very important that the authorities listen and take precautions."

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