Scientists study chemical signatures left by the frictional heat of past earthquakes

By tracking heat-induced chemical signatures, researchers can determine where an earthquake began and ended

“If even a tiny structure within a fault has had an earthquake, we can actually see the difference between how hot that piece of the fault got versus everything outside of it,” geophysicist Heather Savage said.

Scientists have developed a new method for studying past earthquakes. By tracking heat-induced chemical signatures, researchers can determine where an earthquake began and ended, as well as plot its movement across a fault system.
When faults slip, the friction generates intense heat spikes, hot enough to alter organic compounds in rocks. For the past eight years, geoscientists at Columbia University’s Lamont-Doherty Earth Observatory have been working on ways to analyze these chemical alterations.
By contrasting chemical changes in rock samples, researchers can locate the origin of an earthquake within a larger fault system.
“If even a tiny structure within a fault has had an earthquake, we can actually see the difference between how hot that piece of the fault got versus everything outside of it,” geophysicist Heather Savage said in a news release.
Tracking historical changes can help researchers determine whether earthquakes within a regional fault system follow predictable patterns.
“Do they all happen to one side? Are they distributed throughout? Are they all clustered on the weakest material within the fault zone?” Savage said.
This data can help researchers create a kind of heat map.
The analysis methods being developed by Savage and her colleagues at Lamont require a solid foundation of lab experimentation. A variety of rock samples must be subjected to a wide range of temperature and pressure combinations to see how different geological circumstances render different chemical alterations.
“The important step for us is to determine how each of those compounds reacts to time and temperature,” Savage said. “That’s going to tell us about the physics of the earthquakes in that fault, which in the long run could lead to a better understanding of earthquake hazards.”

http://www.themarshalltown.com/2016/12/18/by-tracking-heat-induced-chemical-signatures-researchers-can-determine-where-an-earthquake-began-and-ended/