A team of researchers led by the University of Texas at Austin has recently discovered that an everyday quirk of physics may be a crucial tool in predicting the world’s most powerful earthquakes. According to the experts, a frictional phenomenon may be a critical key in understanding when and how violently faults move. While this alone cannot allow scientists predict when and where the next major earthquake will strike – since the forces behind large earthquakes are very complex – it will nevertheless offer scientists a new way to investigate the causes and potential for damaging earthquakes to occur.
The researchers squeezed rocks collected from a well-studied fault off the coast of New Zealand in a hydraulic press and discovered that they were very slow to heal and slipped easily. Introducing this finding in a computer model used to estimate the earthquake activity in that area, the results pointed towards a small, slow-motion tremor every two years, an almost exact match with observations from the New Zealand fault. Thus, a fault that is slow to heal is more likely to move harmlessly, while one that heals quickly is more probable to stick until it breaks into a large, damaging earthquake – a phenomenon that also explains, for instance, why it takes more effort to shove a heavy box from a standstill than it does to keep it in motion.
“The same physics and logic should apply to all different kinds of faults around the world,” said study co-lead author Demian Saffer, an expert in Geophysics at UT Austin. “With the right samples and field observations we can now start to make testable predictions about how big and how often large seismic slip events might occur on other major faults, like Cascadia in the Pacific Northwest.”
The experts believe that the clay-rich rocks that are common at many large faults may be regulating earthquakes by allowing plates to slip quietly past each other, limiting the buildup of stress.
“This doesn’t get us any closer to actually predicting earthquakes, but it does tell us whether a fault is likely to slip silently with no earthquakes, or have large ground-shaking earthquakes,” explained co-lead author Srisharan Shreedharan, an assistant professor of Geosciences at the Utah State University.
Since at Cascadia, for instance, there is little evidence of shallow, slow-motion tremors, the Pacific Northwest Seismic Network (PNSN) aims to place sensors across key areas of the fault, in order to monitor the possibility of major earthquakes.
“We want to zero in on the processes in the shallow part of the fault because that’s what governs the size of the tsunami,” said Harold Tobin, the director of PNSN. “Fault healing doesn’t explain everything, but it does give us a window into the working of subduction zone faults that we didn’t have before.”
The study is published in the journal Science.
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