A new study revealed that earthquakes can cook "dead" plants and algae trapped in the fault line.
Earthquakes are believed to be brought by a sudden slip on a fault. As fault lines slip, a friction is created, which in the process, causes heat. At times, the heat caused by the friction gets so high it melts rock inside the fault.
"Temperature rise during an earthquake says something about the strength of the fault when it was slipping, and that is a big unknown in earthquake science," said Heather Savage, a geophysicist at Lamont-Doherty Earth Observatory in New York, to LiveScience.com. "These kinds of questions are really fundamental if we're ever going to get better at making accurate earthquake predictions."
However, though there are many visible fault lines on the Earth's surface, there were not much melted rocks to study.
Over time, Savage and her colleagues managed to develop a new way to know more about old earthquakes -- a new thermometer that uses thermal alteration of organic biomarkers that happen to a fault and surrounding materials. Inadvertently, they discovered that slipping faults can cook dead plants and algae trapped in a fault, as well - in a way comparable to how organic materials were converted to eon then to oils.
The team then decided to test if these "cooked" materials can be used to determine the severity of earthquakes. They used earthquake biomarker to analyze cooked materials and melted rocks along a fault in a 60-million-year old subduction zone situated above the shoreline at Pasagshak Point, Kodiak Island.
Subduction zones are the areas where tectonic plate movements occur beneath another tectonic plate movement. The biggest earthquakes are deemed to come from these zones.
The biomarkers -- carbon, hydrogen, and diamondoids - were heated until they take on a similar basic structure as diamonds. After that, they discovered that the earthquake they were looking at was 840 to 1170 degrees Celsius (1540 to 2140 degrees Fahrenheit) hot and approximately a magnitude of 7 or 8.
Savage said that this method, known as earthquake thermometer, only works on faults in sedimentary rocks that carry organic material.
Further details of the study were published in the online journal Geology.
