Geological aspects[edit]
The quakes occurred in a seismic gap which is located between the areas hit by the 2016 August earthquake and the one in Umbria and Marche of 1997. In that gap no strong earthquake happened for more than 100 years[15] until 2016.
As the process of faulting along the chain of the Apennine Mountains is a relatively recent one in geological terms, starting 500,000 years ago, the faults are more irregular, so more shaking occurs due to foreshocks according to seismologist Ross Stein from Stanford University. In this case the destructive shock on 26 October was preceded by the foreshock by two hours, causing people to leave their homes and be safer when the larger shock occurred.[1
the process of faulting along the chain of the Apennine Mountains
faulting along the chain
movements along faults
as a result of compression in the Earth's crust.