The evolution of the 2016 central Italy seismic sequence from geodesy, seismology and field investigation
The destructive 2016 Central Italy earthquake sequence constitutes the largest release of seismic energy in Italy since the 1980 Irpinia earthquake. The sequence started on 24th August with a MW 6.2 earthquake, which was followed on the 26th October and 30th October by MW 6.1 and MW 6.6 events respectively, as well as by hundreds of smaller aftershocks.
Here we use geodesy and bodywave seismology to estimate source mechanisms for each of the major earthquakes, and to estimate the spatio-temporal distribution of seismic and aseismic slip throughout the sequence. Our field measurements of extensive metre and decimetre-scale surface ruptures are used to constrain and to validate our source models. We use our slip estimates to calculate the evolution of Coulomb stress on the causative and surrounding faults throughout the sequence.
We find that each of the MW>6 events involved slip on the Vettore fault, a structure that had not produced earthquakes in the historical record, despite being known to be active over the Holocene. Slip in all events was also largely restricted to shallow (<8 km) depths, possibly related to structural segmentation of the Vettore fault with depth.
We show that these earthquakes have stressed the down-dip extent of the Vettore fault. As this portion of the fault has not failed in the recent seismic sequence or in historical earthquakes, we suggest there is still a potential for large earthquakes on the Vettore fault within a relatively short interval, an occurrence that has precedent in other tectonic regions worldwide.