It’s been a while since seismologists observed some subtle anomalies in underground electrical fields prior to earthquakes, in some cases manifesting a few weeks prior to the moment when an earthquake is triggered.
They are tempted to assume that the electromagnetic bursts can be used to determine when a quake will occur.
Up until recently, the reason why they occur hasn’t been apparent, according to Sciencealert.
New research speculates that the answer may lurk within the gases trapped in what is called a fault valve and may build up before quakes.
The impermeable rock layers sometimes slip across faults, forming a gate that blocks the underground water flow.
When the fault valve cracks and pressure decreases, CO2 or methane dissolved in the water are released, expanding and pushing the cracks furthermore.
As the gas rises, it also gets electrified, with electrons pushed away from the cracked surfaces joining the gas molecules and producing an electrical current as they move upwards.
“The results supported the validity of the present working hypothesis, that coupled interaction of fracturing rock with deep Earth gases during quasi-static rupture of rocks in the focal zone of a fault might play an important role in the generation of pre- and co-seismic electromagnetic phenomena,” the researchers wrote.
With a custom laboratory setup, the team managed to test the reactions of quartz diorite, basalt, gabbro, and fine-grained granite in downscaled earthquake simulations.
They proved that electrified gas currents might have a link to the rock fracture.
The kind of fault appears to have en effect, too – the study suggests that rocks, including granite, have lattice defects that trap unpaired electrons over time via natural radiation rising from below the surface, producing a greater current.