Holocene paleoseismology of the Norcia fault system (Central Italy)

We investigated the Late Quaternary activity of the Norcia fault system, one of the most hazardous seismogenic structures of Italy, responsible over the centuries for nucleating several Mw 6 earthquakes, possibly up to Mw 6.9 as on 14th January 1703. This fault is located only 10 km away from the Mount Vettore fault system, which was responsible for the deadly Mw 6.6 central Italy earthquake in 2016. Using evidence gathered from ten paleoseismological trenches, we reconstructed the history of the strongest earthquakes sourced by the Norcia faults during the past 4 ky, and in previous time-windows back to 20 ka. In particular, we found indications of the historical 1703 and 99 BCE events, as well as a previously unknown one in the Bronze Age. We also obtained a robust estimate of the slip-rate for the post Last Glacial Maximum period (1 ± 0.2 mm/yr), and a rough 1.8 ky recurrence time for ~Mw 6.9 events during the late Holocene.