New research suggests that nucleation fronts are behind the rapid fractures that cause seismic waves.
One slow, creeping movement No shaking may be a precursor to earthquakes, according to a new report published in the journal Nature. The research, led by physicist Jay Fineberg of the Hebrew University of Jerusalem, examines how cracks form and accelerate in materials, providing insights into the physics of earthquakes.
The study reproduces earthquake-like fractures in the laboratory, using Plexiglas sheets subjected to lateral forces, imitating the behavior of tectonic plates on fault lines like the San Andreas Fault in California.
The results suggest that, before a rapid fracture occurs – the type of fracture responsible for seismic waves and tremors in the ground – there is a slower energy production process known as nucleation front.
“When tectonic plates are trapped at a fragile interface, stress builds up over time,” Fineberg explained. This fragile section, unable to deform under tension, ends up breakinggiving rise to an earthquake. However, this process does not occur instantly. First, a crack has to form and expand slowly, in what Fineberg describes as a “precursor phase.”
The team discovered that these nucleation fronts differ from normal fractures in their speed and energy release. Unlike fast-moving fissures that generate kinetic energy and seismic waves, nucleation fronts move slowly and do not cause immediate shaking. This movement, known as “aseismic creep”, allows energy to gradually accumulate.
The study revealed that nucleation fronts must be modeled in two dimensions instead of one. Instead of viewing a crack as a single line separating broken from unbroken material, Fineberg likened it to a growing stain in the plane where two plates meet. Initially, as the spot grows, the energy required to expand it increases proportionally, preventing rapid rupture, explains .
However, when the stain goes beyond the fragile zone, the energy balance changes. Excess energy becomes available, triggering explosive acceleration of the crack that produces an earthquake.
This discovery has implications for earthquake prediction. If scientists could measure aseismic movement along fault lines, it might be possible anticipate disruptions before these occur.
