Researchers simulated deep-fault conditions and found crushed quartz can weld back together rapidly under about 1 GPa of pressure (≈10,000 atm) and temperatures above 900°F (≈482°C). Electron microscopy showed the grains fused into a cohesive material—a process a co-author called "quick-set fault glue." This rapid cementation offers a physical mechanism for how faults regain strength after slow slip events and could alter models of fault behavior and earthquake risk.
How Rocks 'Heal' Themselves Deep Inside Fault Zones — A Possible Key to Slow Slip Events
Researchers simulated deep-fault conditions and found crushed quartz can weld back together rapidly under about 1 GPa of pressure (≈10,000 atm) and temperatures above 900°F (≈482°C). Electron microscopy showed the grains fused into a cohesive material—a process a co-author called "quick-set fault glue." This rapid cementation offers a physical mechanism for how faults regain strength after slow slip events and could alter models of fault behavior and earthquake risk.
02:09 PM, 11/20/2025Science
Earthquakes are often explained as sudden slips along faults where tectonic plates release stored stress. But not all fault movement is abrupt. Slow slip events (SSEs), first identified in 2002, unfold as a sequence of gradual ruptures, pauses and re-ruptures over hours to months, producing only centimeters of net displacement. That cycle—slip, apparent recovery, then renewed slip—has long puzzled seismologists.
Researchers studying seismic activity in a tectonically active sector of the Pacific Northwest report a plausible physical mechanism: rocks at the plate interface can re-cement, restoring strength under the extreme pressures and temperatures found deep in fault zones. The team describes their results in a paper published in Science Advances.
To reproduce post-SSE conditions in the laboratory, the scientists built a vessel capable of maintaining roughly 1 gigapascal of confining stress (≈10,000 atmospheres) and heated crushed quartz above 900°F (≈482°C). After running the experiment under those pressures and temperatures, electron microscopy showed the crushed mineral grains had welded together to form a cohesive, stronger material.
“It’s like quick-set fault glue,” said Amanda Thomas, a geophysicist at the University of California, Davis and a co-author on the paper. “It’s really fast and you can get significant strength recovery.”
The authors argue that this cementation process—rapid mineral welding under high pressure and temperature—provides a physically plausible way for deep faults to regain cohesion after slipping, enabling repeated slow slip cycles. While the experiment focused on conditions comparable to deep SSE-prone faults, the cementation mechanism could also influence the behavior of larger, more seismically active faults.
Understanding these healing mechanisms helps seismologists improve models of fault strength and the timing of future slips. Incorporating rapid cementation into fault models could change assessments of stress recovery, rupture propagation, and earthquake hazard in regions with deep, warm fault zones.