A new study has shed light on the hidden mechanism that could explain how earthquakes “ignite.” Researchers have discovered that a period of slow, creeping movement without any shaking may be a necessary prelude to earthquakes.
The study, which focused on the fundamentals of material rupture, used laboratory experiments with sheets of plastic to examine the physics of fractures. The findings revealed that a buildup of friction at the interface of two bodies transforms into a sudden rupture, releasing kinetic energy into the surrounding material.
According to Jay Fineberg, a physicist at The Hebrew University of Jerusalem, “the same physical process will take place in both cases – the explosive spring of the bent plates will release in the same way.” This process occurs when two tectonic plates moving against each other get stuck, allowing the fault to build up stress.
The research also revealed that the fracture process doesn’t happen all at once. A crack needs to be created, which accelerates rapidly to speeds close to the speed of sound, causing the earth to shake. The key question is how nature creates the crack that becomes an earthquake.
Fineberg and his colleagues investigated this using a mix of theoretical math and laboratory experiments. They reproduced earthquake-like fractures in the lab with blocks made of polymethyl methacrylate, also known as plexiglass. The researchers found that once a crack starts, it acts like a one-dimensional line ripping through the material.
However, before the crack forms, the material develops a precursor phase called a nucleation front. These fronts move slowly through the material but don’t release kinetic energy into their surroundings, making them “aseismic.” Eventually, the patch expands outside of the brittle zone, causing excess energy that needs to be released.
The findings suggest that detecting signs of the transition from aseismic to seismic movement may allow scientists to predict earthquakes. Fineberg and his team are now working on developing methods to detect these signs in laboratory materials, which could potentially uncover what happens during an earthquake before it occurs.
Source: https://www.livescience.com/planet-earth/earthquakes/scientists-find-hidden-mechanism-that-could-explain-how-earthquakes-ignite