For some time, seismologists are aware of brief, subtle anomalies in underground electrical fields leading up to an earthquake, sometimes occurring as soon as a couple of weeks before the quake happens.
It’s tempting to think these electromagnetic bursts might be wont to predict when a quake will strike. Up so far , however, the explanation for the strange bursts hasn’t been clear.
New research suggests that the key lies within the gases that get trapped in what’s referred to as a fault valve & may build up before an earthquake. These impermeable layers of rock can slip across a fault, effectively creating a gate that blocks the flow of underground water.
When the fault valve eventually cracks & pressure decreases, CO2 or methane dissolved within the trapped water is released, expanding in volume & pushing the cracks in the fault. Because the gas emerges, it also gets electrified, with electrons released from the cracked surfaces attaching themselves to gas molecules & generating a current as they move upwards.
“The results supported the validity of this at present working hypothesis, that coupled interaction of fracturing rock with deep Earth gases during quasi-static rupture of rocks in focal zone of a fault might play a crucial role in generation of pre- and co-seismic electromagnetic phenomena,” write the researchers in their published paper.
Using a customized lab setup, the team was ready to test the reactions of quartz diorite, gabbro, basalt, and fine-grained granite in scaled-down earthquake-like simulations. They showed that electrified gas currents could indeed be linked to rock fracture.
The type of rock does make a difference, the scientists found. Rocks including granite have lattice defects that capture unpaired electrons over time through natural radiation rising from below the surface, which results in a bigger current.
And the sort of fault seems to possess an impact also. The study backs up previous research from an same scientists into seismo electromagnetics, showing how CO2 released from an earthquake fault might be electrified & produce magnetic fields.
Other hypotheses about the electromagnetic bursts include the thought that the rocks themselves could become semiconductors under enough strain and with enough heat, while other experts don’t think these weird bursts are predictors in the least.
Until an earthquake is really predicted by unusual electromagnetic activity – activity that happens many on our planet as a matter in fact anyway – the jury remains out. But if this concept is protected by future research, it could give us a life-saving method for getting a heads up-on future quakes.
“As a results of this laboratory experiment, it’d be possible to detect the electrical signal accompanying an earthquake by observing the telluric potential/current induced in conductor, like a steel water-pipe buried underground,” conclude the researchers.
“Such an approach is now undergoing model field tests.”
The research has been published in Earth, Planets and Space.