‘Holy grail’ of earthquake research one step closer to reality as experts develop method that could one day help to predict future tremors
- Experts studied 700 years of historical earthquake records from central Italy
- They used this information to create a model of changing stresses underground
- 97 per cent of quakes from 1703–2016 took place on previously-stressed faults
- The results may help experts work out where future quakes are more likely to hit
Being able to forecast future earthquakes is commonly regarded as a ‘Holy Grail’ of seismological research and researchers are one step closer to the goal.
Analysis of historical disasters in Italy found earthquakes are more likely to strike along faults that have already been stressed by forces from previous tremors.
Researchers led by the University of Plymouth studied accounts of earthquakes going back 700 years to build models of how the stress underground changed.
Scientists have long striven to identify patterns in the seemingly random way that earthquakes strike in hazardous, geologically active regions.
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Earthquakes are more likely to strike along faults that have already been stressed by forces from previous tremors, modelling of historical Italian disasters — such as the 2016 quake that devastated the town of Amatrice — has revealed
Earth scientist Zoë Mildon of the University of Plymouth said: ‘Earthquakes are hugely destructive to both people and property, and the Holy Grail of earthquake science would be to predict where they are going to happen and when.
‘We are a very long way from that, and indeed it may never be possible to accurately predict the location, time and size of future earthquakes.
‘Our research, however, could be a starting point in helping us develop better forecasts of which fault lines might be more susceptible based on previous tremors.’
Dr Mildon and her colleagues studied historical records from the Apennines region of central Italy, which has been hit by earthquakes repeatedly over the last 700 years.
On the surface, the events recorded appear to have taken place at random, with the location of each successive earthquake jumping around the region.
Using advanced modelling techniques, however, the researchers have shown that 97 per cent of the earthquakes between 1703–2016 took place on geological faults that were already either entirely or partially positively stressed by previous quakes.
‘Earthquakes are caused by rock sliding past each other along fault lines, which causes the forces and stress in the surrounding rocks to change after a big earthquake,’ explained Dr Mildon.
‘It is often assumed that the nearest fault to a particular earthquake will be the next to rupture,’ she added.
‘However, our study shows this is never the case, so typical approaches to modelling Coulomb stress transfer have limited potential to improve seismic hazard assessment.’
‘Our model adds the stresses of lots of earthquakes together and shows that in the majority of cases fault lines are positively stressed when they rupture,’ she added.
‘It is a step change in modelling Coulomb stress transfer and shows this is an ignored yet vital factor when trying to explain earthquake triggering.’
Scientists have long striven to identify patterns in the seemingly random way that earthquakes strike in hazardous, geologically active regions. Pictured, Dr Zoë Mildon stands at the face of an exposed fault in the Maiella National Park, in southern Abruzzo, which last moved in 1706
The historical records that Dr Mildon and colleagues studied began in 1349 and described the lives lost and damage brought by about earth movements to individual towns and villages across central Italy,
From these accounts, the researchers were able to infer where and when large earthquakes occurred and feed such into their stress models.
Among the events researchers studied were the series of earthquakes that destroyed the towns of Amatrice and Norcia, killing around 300 people, in the August of 2016.
Although the researchers’ records dated back around 700 years, they concentrated their analysis on the latter half of this period in order to give their model time build a decent picture of the cumulative stresses caused by each subsequent quake.
The full findings of the study were published in the journal Nature Communications.
WHAT CAUSES EARTHQUAKES?
Catastrophic earthquakes are caused when two tectonic plates that are sliding in opposite directions stick and then slip suddenly.
Tectonic plates are composed of Earth’s crust and the uppermost portion of the mantle.
Below is the asthenosphere: the warm, viscous conveyor belt of rock on which tectonic plates ride.
They do not all not move in the same direction and often clash. This builds up a huge amount of pressure between the two plates.
Eventually, this pressure causes one plate to jolt either under or over the other.
This releases a huge amount of energy, creating tremors and destruction to any property or infrastructure nearby.
Severe earthquakes normally occur over fault lines where tectonic plates meet, but minor tremors – which still register on the Richter sale – can happen in the middle of these plates.
The Earth has fifteen tectonic plates (pictured) that together have molded the shape of the landscape we see around us today
These are called intraplate earthquakes.
These remain widely misunderstood but are believed to occur along minor faults on the plate itself or when ancient faults or rifts far below the surface reactivate.
These areas are relatively weak compared to the surrounding plate, and can easily slip and cause an earthquake.
Earthquakes are detected by tracking the size, or magnitude, and intensity of the shock waves they produce, known as seismic waves.
The magnitude of an earthquake differs from its intensity.
The magnitude of an earthquake refers to the measurement of energy released where the earthquake originated.
Earthquakes originate below the surface of the earth in a region called the hypocenter.
During an earthquake, one part of a seismograph remains stationary and one part moves with the earth’s surface.
The earthquake is then measured by the difference in the positions of the still and moving parts of the seismograph.