October 2016 Central Italy earthquakes

A series of major earthquakes struck Central Italy between the Marche and Umbria regions in October 2016. The third quake on 30 October was the largest in Italy in 36 years, since the 1980 Irpinia earthquake.

Earthquakes
A magnitude 5.5 earthquake struck 8 km east southeast of Sellano on 26 October at 19:11 local time (17:11 UTC) at a depth of 10 km. The earthquake was also felt in the city of Rome. In the region of Marche some houses collapsed, Italian media reported. There were also power failures and the telephone lines were interrupted.

A magnitude 6.1 intraplate earthquake struck 3 km west of Visso on 26 October at 21:18 local time (19:18 UTC). The earthquake, which occurred two months after a magnitude 6.2 earthquake in August, struck about 30 km to the northwest of the August earthquake's epicenter. The civil protection, however, estimated the consequences less dramatically than feared. According to official data, a man died because he had suffered a heart attack as a result of the quake.

A third large, shallow earthquake of USGS preliminary magnitude 6.6 struck 6 km north of Norcia at 07:40 local time (06:40 UTC) on 30 October. Early news and social media reports showed heavy damage to some structures. The village of Arquata del Tronto was destroyed, as were several heritage buildings. These include the Basilica of Saint Benedict in Norcia, the Church of San Salvatore and other churches in Campi. Two women died of sudden heart attacks during the quake.

Shocks
(Source: Istituto Nazionale di Geofisica e Vulcanologia)

Magnitude of October 2016 Central Italy earthquakes.

Geological aspects
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 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.

Comparisons with August 2016 earthquake
The map to the left is dated 27 October, before the biggest shock of 30 October.

Earthquakes from August 2016 Central Italy earthquake.