The Earth has been permanently deformed by cracks from the earthquakes in Chile, new research suggests. Scientists previously thought the Earth rebounds after earthquakes. In previous models, damaged chunks of the planet's crust would elastically rebound. This would, perhaps, take months or even decades, but eventually, the crust would be back in the the condition it originally was. This phenomeona was the case in the wake of the 1906 San Francisco temblor that destroyed over 80 percent of the city. Scientists first observed it then, and it has since been extensively backed up by satellite-based GPS systems that monitor Earth's movements. 

Surprising new research suggests this is not always the case. Richard Allmendinger, a structural geologist from Cornell University, and his colleagues have discovered that major earthquakes of magnitude 7 or greater apparently caused the crust in the Atacama Desert of northern Chile to crack irreversibly.

"My graduate students and I originally went to northern Chile to study other features," Allmendinger said in a statement. "While we were there, our Chilean colleague, Professor Gabriel González of the Universidad Católica del Norte, took us to a region where these cracks were particularly well-exposed."

"I still remember feeling blown away - never seen anything like them in my 40 years as a geologist - and also perplexed," Allmendinger said to OurAmazingPlanet. "What were these features and how did they form? Scientists hate leaving things like this unexplained, so it kept bouncing around in my mind."

In northern Chile, "the driest place on Earth, we have a virtually unique record of great earthquakes going back a million years," Allmendinger said. Most records of ancient earthquakes can only measure cycles of two to four quakes, "our record of upper plate cracking spans thousands of earthquake cycles," he noted.

"It is only in a place like the Atacama Desert that these cracks can be observed - in all other places, surface processes erase them within days or weeks of their formation, but in the Atacama, they are preserved for millions of years," Allmendinger said. "We have every reason to believe that our results would be applicable to other areas, but is simply not preserved for study the way that it is in the Atacama Desert," he added.

The journal Nature Geoscience has an article detailing the findings of Allmendinger and his colleagues.

In the Atacama, records remain of a large number of quakes; thus researchers are more easily able to see patterns. Their findings were remarkable: they determined that 1 to 10 percent of the deformation of the Earth caused by 2,000 to 9,000 major quakes over the past 800,000 to 1 million years was permanent. Cracks in the desert crust will not spring back elastically, as previously assumed.

Allmendinger said that his new study "calls into question the details of models that geophysicists who study the earthquake cycle use," and suggests "the models will have to be rethought".

More elements of their findings are detailed in the April 28 issue of Nature Geoscience.