Earthquakes of varying strength erupt along so-called fault lines, where two masses of earth violently slip past one another. The powerful grinding of rock on rock creates an incredible amount of friction, heat and chemical reactions.
As the rocks slip past each other, they can create a series of tremors or shocks felt all the way up on the surface.
The largest tremor, known as the mainshock, strikes at the epicentre and is often preceded by weaker foreshocks.
Geologists, however, cannot tell the difference between the two until after the mainshock hits.
Because of this, earthquake predictions are impossible to make to any degree of accuracy.
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But a team of engineers at Duke University in North Carolina, US, is making headway into better understanding the mechanical processes that allow earthquakes to erupt in the first place.
Although the research does not yet open the floodgates for precise earthquake forecasting, the engineers involved believe they are on the right track.
Professor Manolis Veveakis from Duke said: “We still cannot predict earthquakes, but such studies are necessary steps we need to take in order to get there.
“And in theory, if we could interfere with a fault, we could track its composition and intervene before it becomes unstable. That’s what we do with landslides.
“But, of course, fault lines are 20 miles underground and we currently don’t have the drilling capacity to go there.’
Professor Veveakis and research scientist Hadrien Rattez have devised a new model that predicts the behaviour and origins of an earthquake in different types of rock.
Such studies are necessary steps we need to take in order to get there
Professor Manolis Veveakis, Duke University
The model provides much-needed insight into the geological processes taking place deep underground, where temperatures and pressures reach incredible levels.
Dr Rattez said: “Earthquakes originate along fault lines deep underground where extreme condition can cause chemical reactions and phase transitions that affect the friction between rocks as they move against one another.
“Our model is the first that can accurately reproduce how the amount of friction decreases as the speed of the rock slippage increases and all of these mechanical phenomena are unleashed.”
The model was published on January 17 in the journal Nature Communications.
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In their experiments, the researchers simulated the conditions within a fault by squeezing and grinding together two discs of rock at high speeds.
By applying pressure and friction, the rocks are superheated and start to melt before glowing bits of rock fly off in every direction.
The experiments reach pressures of 1,450 pounds per square inch and speeds of one metre per second.
For reference, the Pacific tectonic plate is estimated to travel at about 0.00000000073 metres per second.
Professor Veveakis said: “In terms of ground movement, these speeds of one meter per second are incredibly fast.
“And remember that friction is synonymous with resistance.
“So if the resistance drops to zero, the object will move abruptly. This is an earthquake.”
The engineers ran their model though computer simulations to determine friction drops across a wide range of faults.
These faults include rocks such as halite, silicate and quartz.
Dr Rattez said: “The model can give physical meaning to observations that we usually cannot understand.
“It provides a lot of information about the physical mechanisms involved, like the energy required for different phase transitions.”
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