It’s virtually impossible to predict when and where an earthquake will occur. Depending on your location and how big the earthquake is, warning times range from a few seconds to a few minutes. But that hasn’t stopped scientists from trying their best to extend this early warning window by as much as possible. Even an hour’s notice could save thousands of lives in a single major earthquake incident.
A new study suggests that the most dramatic quakes may be preceded by a subtle, slow creep — an unassuming phase that may hold the key to understanding the mechanics of rupture.
Perhaps all the more intriguing, this insight comes not from fault lines but from a laboratory experiment involving sheets of plastic.
The Prelude to Rupture
“First, a crack needs to be created,” Jay Fineberg, the lead researcher of the new study and a physicist at The Hebrew University of Jerusalem, explained for Live Science. This crack, or rupture, begins where two tectonic plates meet. The plates are stuck at a brittle interface — a thin rigid zone that resists deformation. Over time, stress builds up as the plates press against each other. Then, seemingly without warning, the crack accelerates to near the speed of sound, shaking the Earth and releasing pent-up energy.
But how does this explosive rupture begin? Fineberg and his colleagues sought answers by studying how cracks form in sheets of polymethyl methacrylate, or plexiglass. Though plexiglass is far removed from the rocky depths of Earth’s faults, the forces at play are strikingly similar. The team recreated earthquake-like conditions by clamping sheets together and applying shear forces, mimicking the movements along faults like California’s San Andreas.
What they observed was surprising. Before the catastrophic rupture, the material exhibited a slow, creeping phase called a nucleation front. These nucleation fronts move at a snail’s pace compared to the rapid fractures that cause seismic waves. That’s a good thing: it means you can observe this phenomenon to perhaps predict with relatively high confidence whether a major earthquake is about to occur. Essentially, this aseismic motion — devoid of the kinetic energy that generates shaking — could be the quiet precursor to an earthquake.
The Energy Equation
To understand this slow movement, Fineberg and his team expanded their mathematical models. Instead of treating the crack as a simple line separating broken and unbroken material, they reimagined it as a patch expanding in two dimensions. This change revealed a critical insight: the energy required to expand the patch increases with its perimeter. As long as the energy demand stays balanced, the patch moves slowly, remaining in the aseismic phase.
Eventually, though, the patch grows beyond the brittle zone. Here, the balance shifts. Excess energy accumulates and transforms the slow creep into a runaway rupture. “This extra energy now causes the explosive motion of the crack,” Fineberg said.
In 2014, Fineberg and colleagues overturned a 500-year-old understanding of friction established by Leonardo da Vinci. Through laboratory experiments simulating earthquakes, they discovered that friction — the force governing how objects slide — relies fundamentally on fracture, the breaking of connections between two surfaces.
Using blocks with rough, interlocking contacts to mimic tectonic plates, the team showed that motion occurs only when these connections are ruptured in an organized sequence, a process governed by fracture mechanics. The rupture propagates at speeds near the speed of sound, releasing energy and enabling the surfaces to slide. This revelation linked two seemingly distinct processes, redefining the physics of how things break and move.
Promising but with Limitations
Now, all this experience may lead to something truly amazing. The implications are profound. If scientists could detect this aseismic phase in real faults, it might be possible to predict earthquakes before they strike.
“In the lab, we can watch this thing unfold and we can listen to the noises that it makes,” Fineberg said. “So maybe we can uncover what you can’t really do in a real fault, because you have no detailed information on what an earthquake is doing until it explodes.”
Easier said than done, though. Many faults experience aseismic creep over long periods without leading to earthquakes, making it difficult to identify when a slow rupture might transition to a catastrophic one in the real world. It remains to be seen whether these findings can be translated into a major advancement in earthquake early warning systems.
Still, this research offers hope for improving our understanding of fracture mechanics in other contexts. The same principles may apply to airplane wings, bridges, or other mechanical structures under stress. By identifying the subtle signs of impending failure, engineers could prevent disasters before they occur.
The findings appeared in the journal Nature.
