Fault healing behavior could provide insight into area seismicity: study

WASHINGTON: Observing the healing behavior of a defect could provide a window into the seismicity of the fault zone, according to the scientists.
A blemish that is slow to heal is more likely to move harmlessly, while one that heals quickly is more likely to stick around until it breaks into a large, damaging one. earthquakethey said in a study.
Scientists at the University of Texas at Austin in the United States have found that a phenomenon of friction could be key to understanding when and how violently defects move, the study found.
Indeed, the phenomenon, which explains why it takes more effort to move a heavy stationary box than to keep it moving, governs how quickly fault surfaces bond or heal after an earthquake, according to the study.
A daily oddity of physics could be an important missing piece in scientists’ efforts to predict the world’s most powerful earthquakes, according to the study published in the journal Science.
This alone won’t allow scientists to predict when the next big earthquake will strike – the forces behind large earthquakes are too complex – but it does give researchers a valuable new way to investigate the causes and potential of a large destructive earthquake, the authors said.
“The same physics and logic should apply to all types of faults around the world,” said study co-lead author Demian Saffer, director of the Institute of Geophysics at the University of Texas, United States.
“With the right samples and field observations, we can now begin to make testable predictions about the magnitude and frequency of large seismic slips that could occur on other major faults, such as Cascadia in the northwest. of the Pacific,” Saffer said.
To make the discovery, the researchers devised a test combining rocks from a well-studied fault off the coast of New Zealand and a computer model, to successfully calculate that a harmless type of earthquake “in slow motion “would occur every few years because the clay-rich rocks inside the fault are very slow to heal, the study said.
According to the study, the rock samples the researchers tested were drilled about half a mile below the seabed in a fault in New Zealand. They pressed the rocks from the fault zone in a hydraulic press and found that they were very slow to heal and slipped easily, he said.
When they plugged the rock data into a computer model of the fault, the result was a small slow-motion tremor every two years, an almost exact match with observations of the New Zealand fault, according to the study. .
Researchers believe that clay-rich rocks, which are common to many large faults, could regulate earthquakes by allowing plates to slide quietly past each other, limiting stress buildup.
“The finding could be used to determine if a fault is likely to slip during large and destructive earthquakes,” said study co-lead Srisharan Shreedharan, a researcher affiliated with the University’s Institute of Geophysics. from Texas.
“It doesn’t get us close to predicting earthquakes, but it tells us whether a fault is likely to slip silently without an earthquake, or have large earthquakes,” Shreedharan said.
At Cascadia, there is little evidence of shallow, slow tremors. This is one of the reasons the Pacific Northwest Seismic Network wants to place sensors in key areas of the fault, according to the study.
“The new study gives them the framework to do that,” network director Harold Tobin said.
“We want to focus on processes in the shallow part of the fault because that’s what governs the size of the tsunami,” said Tobin, who was not part of the study.
“Fault healing doesn’t explain everything, but it gives us a window into how subduction zone faults work that we didn’t have before,” Tobin said.
The New Zealand rock samples were collected during a scientific ocean drilling mission in 2018.

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