New tool could provide insight into powerful future earthquakes

An everyday quirk of physics could be a valuable new way to study the causes and potential for major harm earthquake happen, such a study.Researchers at the University of Texas at Austin, USA, discovered that a friction phenomenon could be the key to understanding when and how severe a fault – a fracture or a zone – is fractures between two boulders – moves. The phenomenon, which explains why it takes more effort to push a heavy box from a standstill than to keep it moving, determines how quickly fault surfaces bond or heal after an earthquake, they said. The study, published in the journal Science, shows that a slow-healing bug is more likely to move harmlessly, while a fast-healing bug is more likely to remain stuck until it ruptures in a large, damaging earthquake.
The discovery alone doesn’t allow scientists to predict when the next big earthquake will strike because the forces behind big earthquakes are too complex, the researchers said. However, it offers a valuable new way to study the causes and potential for a large, damaging earthquake, they said.
“The same physics and logic should apply to all different types of faults around the world,” said study co-lead author Demian Saffer, director of the University of Texas Institute of Geophysics at the Jackson School of Geosciences.
“With the right sampling and field observations, we can now begin to make testable predictions of how large and how often large seismic slide events could occur on other large faults like Cascadia in the Pacific Northwest,” Saffer said. The researchers developed a test that combined rocks from a well-studied fault off the coast of New Zealand and a computer model to successfully calculate that a harmless slow-motion earthquake would occur every few years because the fault is very slow to heal . The rock samples they tested were drilled about half a mile below the sea floor in a fault in New Zealand. The researchers compressed the rocks of the fault zone in a hydraulic press and found that they healed very slowly and slipped easily. When they fed the rock data into a computer model of the fault, the result was a small slow-motion tremor every two years, a near-exact match to observations of the New Zealand fault.
Researchers believe the clay-rich rocks common to many large faults may regulate earthquakes by allowing plates to slip quietly past one another, limiting the build-up of stress. The discovery could be used to determine whether a fault is prone to shedding during large, damaging earthquakes, said study co-leader Srisharan Shreedharan, associate researcher at the University of Texas Department of Geophysics and an assistant professor at Utah State University. “This doesn’t get us any closer to actually predicting earthquakes, but it does tell us whether a fault is likely to slide silently without earthquakes or have large, ground-shaking earthquakes,” he added.