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Earthquakes can be preceded by subtle, slow motion, study finds, offering new possibilities for improving early warning systems and preventing disasters
Avoiding an earthquake is still an almost impossible task, despite the scientific advances. However, a recent study has shed new light on what may be a precursory sign before the most catastrophic earthquakes.
Based on laboratory experiments, scientists have identified a slow, subtle movement that could be a key to extending an early warning window.
The mystery of the beginning of the rupture
Earthquakes occur when tectonic plates, large pieces of the Earth's crust, move abruptly. This movement occurs along fault lines, where the plates meet and press against each other for long periods of time.
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Eventually, the pressure builds up and causes a rupture, releasing a huge amount of energy and causing the tremors. But what puzzles scientists is how this rupture begins. How can we predict this initial moment?
Jay Fineberg, physicist at Hebrew University of Jerusalem and leader of the study, explains that the rupture begins in a broken zone, where the plates are stuck.
As the stress increases, the rupture accelerates until it reaches nearly the speed of sound, generating an earthquake. But before this explosion, there is a calmer, slower phase that could be observed to predict a disaster.
The plexiglass experiment
Although fault lines run miles underground, the study did not focus directly on them. Instead, the scientists recreated fault conditions in a laboratory setting using sheets of polymethyl methacrylate, also known as plexiglass.
The team applied shear forces to the sheets, simulating the movements of tectonic plates, especially as they occur in California's famous San Andreas fault.
What they found was surprising. Before a catastrophic rupture, the material went through a phase called a “nucleation front,” an extremely slow, almost imperceptible movement.
This phase is much gentler and more creeping than the rapid, intense tremors that mark earthquakes. For scientists, this has opened up a new possibility: if this subtle movement could be detected, it might be possible to predict the arrival of a major earthquake.
The mechanics behind slow motion
Fineberg’s team went further and expanded the mathematical models to understand the crack’s behavior. Instead of viewing the rupture as a simple line, as was traditionally done, they reimagined it as a patch that expanded in two dimensions.
This new model revealed a crucial point: while the increase in energy required to expand the patch was balanced, the motion remained slow and aseismic.
However, when the patch exceeded the limit of its brittle zone, excess energy accumulated and the rupture accelerated, becoming explosive.
Implications and challenges
The findings offer an optimistic outlook for improving earthquake early warning systems. If it is possible to detect this aseismic phase on real faults, it will give scientists more time to issue warnings.
According to Fineberg, in the laboratory it is possible to hear the sounds emitted by this movement, but in reality, since faults are not as visible, many faults exhibit this slow movement without resulting in an earthquake, which makes the task of predicting the exact moment even more complex.
Despite the difficulties, this research opens doors to the development of new monitoring and prevention methods.
And not just for earthquakes. These same principles can be applied to the study of other systems under stress, such as airplane wings or bridges, offering a way to detect failures before they become catastrophic.
With information from Live Sciense.
