Italy's National Institute of Geophysics and Volcanology (INGV) said the quake struck at 15:48 (14:48 GMT), with its epicentre in Garfagnana.

BBC: Italy: Earthquake hits near Bologna

Alessandro Amato of the INGV said the latest tremor "came out of nowhere", and described it as a classic earthquake for the area - "medium-strong" and "fairly shallow".

BBC: Italy: Earthquake hits near Bologna

Raffaele Azzaro, first researcher at INGV-CT, told CNN that one local faultline has moved by as much as 17 centimeters in one day, and currently moves at a rate of around three centimeters each year.

CNN: Keeping track of Etna's pulse

Volcanologist Sonia Calvari, of the Institute of Geophysics and Volcanology in Catania (INGV-CT), said rapid advances in technology enable experts to use a wide range of methods to continually map and monitor Etna from a distance.

CNN: Keeping track of Etna's pulse

Fabio Picuti, the public prosecutor, stresses that the charge is not about whether the experts, who included Enzo Boschi, then president of the National Institute of Geophysics and Vulcanology (INGV), should have predicted exactly when, where and with what force the earthquake would have struck.

ECONOMIST: An extraordinary manslaughter trial starts in Italy

Indeed, Warner Marzocchi and Anna Maria Lombardi of the INGV showed that a few hours before the earthquake actually struck modelling would have suggested the chance that a powerful quake would occur within 10 kilometres of L'Aquila within three days rose from one in 200, 000 (the background level) to about one in 1, 000.

ECONOMIST: An extraordinary manslaughter trial starts in Italy