The 2016 Amatrice-Vettore Earthquakes: linked faults, multiple earthquakes and repeated rupture.
The Amatrice-Vettore Earthquake sequence ruptured in three separate main shocks on the 24th August (Mw 6.2), 26th Oct (M 6.0), and the largest on the 30th Oct (M 6.6). Sequences of earthquakes of similar or larger magnitudes are common in the historical catalogue in central Italy. Here we report on the complicated nature of this sequence using multiple techniques and observations at a range of spatial and temporal scales.
The first earthquake ruptured across two faults systems thought previously to be separate, even independent, structures – the Laga and Vettore faults. Two months later, the second event occurred along the northern end of the Vettore fault, which did not fail in the previous event. Based on radar interferometry (InSAR) and body wave seismology, both of these events ruptured shallow and long patches with ~20 cm of slip observed along portions of the ruptures at the surface. The largest earthquake shortly followed, and preliminary InSAR models suggest that the deeper portion of the Vettore fault accommodated significant slip but propagated to the surface along the same patches that broke in the previous two events, with greater than 1.5 m of displacement measured in places.
We will show preliminary results from satellite radar and field observations (including extensive laser scanning and mapping of the ruptures), and discuss these observations in the context of how the sequence evolved in time and space. We highlight the important observation of surface rupture along the same >6 km segment in the first and last event, and what this implies for the preservation of earthquake sequences in the geological record. These events are critical for understanding how faults form hard links and how the disconnected nature of faults in central Italy lead to sequences of events, rather than a single larger-magnitude earthquake.