Just this weekend, a powerful 6.6M quake struck Italy. It took place within the region that experienced another back in August, one that resulted in the deaths of more than 300 people. Remarkably, no one was killed this time, despite it being the most powerful quake to hit Italy since 1980.
Either way, this new event appears to be one of many that have shaken the country recently. So why are there so many earthquakes happening there right now?
Italy is prone to earthquakes thanks to its particularly unusual geological setting. It’s positioned along several active fault networks in the colossal battle between the Eurasian and African tectonic plates. The latter is ramming into the former at a rate of around 2 centimeters (0.79 inches) every year, which builds up tension and creates new faults.
This collision has been responsible for constructing the Apennines, a mountain range that runs through the north of the nation like a spinal column. It is within these mountains that the recent August and October quakes have taken place, along with their numerous, fairly powerful aftershocks.
The faults that slipped forwards suddenly in both cases were “normal” faults, wherein one chunk of rock slides down relative to the other side. They were set loose by the extension of the Tyrrhenian Sea, part of the Mediterranean Basin off the western coast of Italy.
The location of this Sunday's earthquake. The shaking reached as far as Naples. USGS
In effect, the opening up of the Tyrrhenian is pulling apart the Apennines and causing faults to rupture. This is sometimes referred to as extensional faulting, and it’s the very same mechanism that caused the devastating 2009 Aquila quake that killed 309 people and sparked a highly controversial legal battle.
A subduction zone in the Adriatic to the east – where one plate section is diving beneath another – is also contributing to the region’s earthquakes by generating stress. Nevertheless, the primary cause of Italy’s destructive tremors right now appears to be down to the aforementioned expansion.
This won’t show any signs of stopping for at least several million years. Consequently, powerful quakes will continue to occur for many thousands of generations to come.