Earthquakes in Chile have cracked and deformed the Earth, according to a news study on quakes in the South American country. While tremors have been known to wreak havoc on the planet’s surface, more than 100 years of research suggests that the Earth mostly rebounds from them.
Blocks of the world’s crust have been seen springing back to where they were before over the course of months and sometimes years.
This kind of rebounding was first seen during investigations of the devastating 1906 San Francisco earthquake, which caused the destruction of more than 80 percent of the city.
The rebound can now be documented through satellite-based GPS systems that monitor how the Earth moved. But structural geologist Richard Allmendinger of Cornell University, along with his colleagues, believe that major earthquakes of magnitude 7 or more have caused the earth’s crust in northern Chile to crack permanently. Allmendinger explained:
“My graduate students and I originally went to northern Chile to study other features. While we were there, our Chilean colleague, Professor Gabriel Gonzalez of the Universidad Catolica del Norte, took us to a region where these cracks were particularly well-exposed.”
Allmendinger recalled being both awe-struck by the features and also curious as to how they formed. The marks and cracks in the Earth gave him and other researchers a unique record of earthquakes going back for millions of years. Allmendinger added that most analyses of ancient earthquakes only probe cycles of two to four of the ancient tremors. However, with Chile “our record of upper plate cracking spans thousands of earthquake cycles.”
The record helped the researchers examine their average behavior over a much longer time period. They discovered during the research that a small but significant 1 to 10 percent of the deformation of the earth caused by 2,000 to 9,000 earthquakes over the past 800,000 to one million years was permanent. Allmendinger explained:
“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. 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.”
The findings were published in the journal Nature Geoscience on April 28.
[Image via ShutterStock]