Earth's Crust Permanently Deformed by Chile Earthquakes: Scars that Don't Heal

Earth can usually spring back after earthquakes, rebounding and reforming over the course of months to decades. Yet new research reveals that some quakes are just too scarring for Earth to properly heal. It turns out that major earthquakes in Chile changed our planet's crust permanently.

Our planet has surprising elasticity. After quakes, Earth can spring back to its former shape. For example, after the devastating 1906 San Francisco quake that destroyed almost 80 percent of the city and killed 3,000 people, scientists saw that the crust actually rebounded. Now the phenomenon is usually observed through the use of satellite-based GPS systems that monitor Earth's movements.

This latest study, though, reveals that Earth can't always recover. Researchers travelled to northern Chile in order to study other geological features. Yet what they found was completely unexpected. They saw large cracks in the Earth's surface--a surprising feature. At first, the scientists were baffled as to how they had formed.

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

Northern Chile has an earthquake record that goes back a million years. While most analyses of ancient earthquakes only probe cycles of two to four quakes, the researchers found that the record of upper plate cracking spans thousands of earthquake cycles.

So how did the scientists see these cycles? It's all recorded in the rocks. The researchers were able to examine the number of earthquakes captured in northern Chilean rocks and record their average behavior over a long period of time. They found that a small but significant one to ten percent of the deformation of the Earth caused by 2,000 to 9,000 quakes was actually permanent. These deformations included cracks that ranged from a scarce few inches to a massive feet in the crust of the Atacama Desert.

This research actually has major implications when it comes to the study of earthquakes. In particular, it calls into question current models that geophysicists use to study earthquake cycle, according to LiveScience. Because the models currently are based off of the idea that no damage is permanent, the recent findings could mean that these models would need to be reworked.

The findings are published in the journal Nature Geoscience.